Blog entries tagged with "power"

A month ago I was able to compare four months of usage between last year and this year. I have received my electricity bill for August which means I can extend that comparison out to six months.

The numbers from 2023:

Gas:

Electricity:

For this six month period in 2023 my total energy cost was $2,078.65.

Then for 2024:

Gas:

Electricity:

These two additional months are the middle of winter so the usage is what I expected, but you cannot argue that $449.31 is a lot less than $2,078.65

I also was able to update my view of my consumption:

Something I noticed with the additional data is that for July I both consumed more electricity and my solar generated less, this aligns with it being a cold and dark month. August had more than normal sunny and warm days, which can be seen in lower comsumption and higher solar generation.

This is all I have to say about this update, I think the next update I give with this amount of detail will be at the end of year when I will be able to see how the numbers go over spring and the start of summer.

Although I should wait until I have a full year’s worth of usage data (or possibly wait for multiple year’s worth) I realised that I could make a comparison of the last four months against the same four months last year. Why four months? Because that is a period of time since my solar was fully set up and that aligns with the two monthly cycle for the gas bills.

Let’s start with some numbers from 2023:

Gas:

Electricity:

This means that for this four month period in 2023 my total energy cost was $1200.95. (it is a coincidence that this is almost a round number…)

So how about 2024:

Gas:

Electricity:

So the total amount I was charged for these four months in 2024 was $258.86. This is a lot less than the same period in 2023, around 80% less which is quite nice.

However this is only one perspective of my usage, the amount of energy fed in or out as seen by the smart meter. How much energy am I consuming? For that I can go to the monitoring for my solar panels:

The first thing that I noticed was that the Enphase Envoy is consistently measuring values that are about 10% lower than what my smart meter is measuring. For the purposes of this comparison I have adjusted the Enphase consumption value up by 10%.

This has given a result I did not quite expect.

• When I had gas heating and resistive hot water in 2023, my electricity consumption for these four months was 1896kWh.
• Then in 2024 with heat pumps for heating/cooling rooms and heating hot water, the electricity consumption for the four months was 1561kWh.

So even without taking into account the gas usage, I am now using 335kWh less electricity? This is a good overall result.

I also need to ask, what would I have paid if had only changed the heating and hot water? The daily charge would have remained and if I assume the same 22.6c/kWh rate my overall bill would have been $483.50. This is only slightly lower than what I had paid for electricity in 2023, so not having a $738 for gas really stands out, and based on how the gas rates were increasing, that would have been nearer $1000 in 2024.

I think I could make the following conclusions:

1. Switching away from gas is worth it and gives the biggest difference of not having that $738 bill, even if you only take into account the financial aspect
2. Adding solar panels gives a decent financial benefit, in this case reducing the cost by half from $483 to $258.
3. Moving to heat pump for hot water gave a smaller, my previous estimates were that it halved the electricity needed, so from $100 to $50 for the four months

I did mention that gas prices were already going up, and my electricity rate increased at the start of August from 22.6c/kWh to 27.7c/kWh. This is combined with my feed-in rate already dropping from 5.4c/kWh to 5.0c/kWh at the start of July. I need to think about more/better ways to self-consume my solar generation, and if this trend continues I might consider batteries sooner than later…

Today is the winter solstice and over the last few days it has been quite clear that winter has set in in Melbourne with headlines such as “Melbourne shivers through coldest winter day in four years…” so it seems appropriate I give some updates on how my solar, AC and heat pump hot water system are going.

A big question I asked myself was whether I made a mistake in getting my gas disconnected. Previously I would have the central heating on a schedule that I didn’t think about and my entire house would be warm at the times that I was awake. The AC units in my study (during the day while I am working and then in the evening) and bedroom (a bit in the morning for when I wake up and then a bit in the evening before I go to sleep) do a good job if I close the doors to those rooms, which means the other rooms (kitchen, bathroom, lounge) are cold.

It isn’t actually that bad, but it is noticeable when I move from room to room. Thanks to my monitoring I could also track that when I was in my study that the CO₂ would climb to 1500ppm and at times I do feel a bit sluggish. My mitigation so far has been to get up every hour and go get a drink or go to the bathroom, this lets enough fresh air in to drop the CO₂ down to around 600ppm from where it will start to climb again. The alternative is to leave the door open (like I used to do) but then the AC unit is trying to heat my entire house which is not efficient.

With the shorter and cloudier days there has been a noticeable drop in how much my solar panels are generating. At the peak of summer they would generate almost 30kWh over the day, but the best I have seen recently is 17kWh on a day that was sunny all day, but that is the difference between 13 hours of sun high in the sky versus about 8 hours of sun that is lower. Though even on a day that rained all the way through the panels managed to produce around 3kWh which was about a third of my consumption for that day.

I could also notice a pattern of the solar generation being best in the early afternoon, the day would start out cloudy and the clear up for a bit. To better take advantage of this I changed the schedule on my heat pump hot water from 10am to 1pm with the intent to run it both from solar that I am generating and also to be in a warmer part of the day so it should run a bit more efficiently. I don’t have a way to actually measure this, but it seems like the right thing to do. What I can also see is that where it would run for just over an hour when the ambient temperature was above 20°C, but now when the ambient temperature is below 10°C it is running for a bit over two hours.

All of this is just the detail, what really matters is the long term so it won’t be until the start of next year that I can sit down with the data and compare 2023 with gas heating and no solar against 2024 with solar and three heat pumps…

It has been a month since I last mentioned my solar panels and this time the significant thing is that I have received my electricity bill for the first full month since everything has been set up. No partial feed-in tariff and no admin charges.

It is pretty much as I expected with what I get paid for the solar balancing out what I am charged for pulling from the grid, leaving the daily charge:

I can’t compare the reported usage against what Enlighten reports because my Envoy gateway has been a bit broken (but now replaced). After the long power outage earlier in February it failed to report to the cloud, although the Home Assistant integration was able to pull data from it just fine. Even then Home Assistant data isn’t complete as the Envoy would at times drop off the network, but llowing for some missing data the usage values do line up.

So how does this compare against a time before I got the solar installed. That would be October 2023:

It is nice that my monthly bill is now a quarter of what it used to be, although I expect it to rise as we head into the colder months when there is less sun and I will be using electricity for heating. No more gas bill though :)

When the previous owners of my place renovated the kitchen they put the power for the dishwasher directly behind the dishwasher instead of the correct location in an adjacent cupboard. This didn’t directly affect me until that dishwasher needed replacing and there was now not enough clearance for the plug.

I replaced the dishwasher over two years ago and my temporary solution was to have the cable coming out of a gap in the side panel and up to a power point above the bench. Last week I finally had an electrician in for a couple of changes which included replacing the kitchen downlights (from 300W of halogen to 48W of LED), replacing a failing bathroom exhaust fan and adding a power point to the cupboard next to the dishwasher.

However this meant that the Tasmota based smart power plug is now also located in the cupboard. I could no longer hit the button on it to turn on power to the dishwasher.

So I started to think about some kind of remote panel button/display that could be mounted on the wall above the dishwasher. As I am still building my projects around the D1 mini I was able to put this together from the variety of shields and bases I picked up a while back:

Unlike my clocks where I wrote a minimal program that communicated via MQTT, this time I decided to try setting this up using ESPHome which I had used to interface with my AC units. It was only a few minutes until I had a button and an RGV light showing up in Home Assistant.

I now started on the more complicated part which was deciding what logic I wanted and then implementing it as automations. So far I have the following:

First is the action to take if the button is pressed:

• if power is off, then turn on power
• if power is on AND dishwasher not active, then turn off power

Then the behaviour of the LED:

• if power is off, then LED is off
• if power is on:
  • if dishwasher active, then LED is blue
  • if dishwasher has been active since the power was last turned on, then LED is green
  • if dishwasher has not been active since the power was last turned on, then LED is red

I can now see at a glance if the dishwasher is running, if it needs emptying or if it is on and shouldn’t be. The next step will be to work out an enclosure, I am leaning towards something based around a wall place and spacer block like I did for my bathroom clock/sensor:

I’m thinking of a small hole for a button to protrude through, and then see how well the LED just shows through the plastic.

There are plate that exist for commercial applications for things like running AC after hours that are a push button and a neon indicator in a two gang plate, but those are quite large (in depth as they are intended to mount in the wall, not on the surface of tiles like I want) and also very expensive, even if all I wanted was the housing for the neon indicator that I would retrofit the LED into…

Today my gas service was abolished.

This sounds fancy but what it means in practice is that I no longer have natural gas service to my house. The meter has been removed and it has been turned off at the main. It was only four months ago that I kicked of these changes by thinking about how expensive my gas bill was getting.

Although I stopped using gas two months ago I had been procrastinating about making the call, it was Daniel Bowen’s post about his experience that prompted me to get around to it.

On 22 January 2024 I called up my retailer to start the process. They emailed me a form to fill in and return which I did the same day. Then silence.

I use the same retailer for gas and electricity and as it happens on the Wednesday there was a form to fill in regarding the feed-in for solar. More silence.

To ease my mind on the Friday I called up and was able to confirm that both forms had been received and had triggered the next stage of each process. So time to wait.

A bit after 11AM today I noticed a truck with the logo of the gas distributor pull up and two workers get out. I didn’t need to speak to them but I wanted to make sure they only disconnected my gas service and did not affect the other unit as they still use gas. They said they first locate the services and then based on that will either just remove my meter and cap the pipe, or remove my meter and turn it off at the main.

It took them around an hour for:

1. locate both gas and water for both units
2. locate the gas and water mains on the nature strip across the road
3. dig down to the gas main
4. shut of my connection at the main
5. confirm that was shut off to my meter
6. remove my meter
7. cut the service pipe off at ground level
8. fill in the hole in the nature strip

I now expect to get my final bill with a $242 abolishment charge ($220 ex-GST), but that is ok as I will no longer have a $1/day charge (so $365/year) for a service I am not using.

There is still some pipework and the entire central heating still in place, but there is no urgency in removing those. In fact I have been wondering if it would be possible to repurpose the ducting, just running the fan to circulate air around my house…

Update 22 February 2024:

Received my final gas bill with the abolishment charges being:

Abolishment Admin Fee                       $  33.00
Gas Service Order                           $  76.65
Added SO# 1202394 Service Line Abolishment  $ 165.35

The two service orders add up to the expected $242, then on top was the $33 admin fee charged by my retailer.

So far this summer the weather has been pretty mild so it is odd to think that we are now in February and this is the first time that we have had temperatures in the high thirties. Based on my measurements we reached 36.2°C yesterday and 38.4°C today.

So how did my new air conditioners handle the heat?

I am still working out how I want the schedules and automation to work, but so far I have it that a calendar entry for 24#COOL#STUDY means that I will allow the study unit to be running at 24°C in cooling mode. The automation looks at the current outside and indoor temperatures and will not start the AC until they both reach 24°C

On Saturday that condition was met at 2PM and kept my study at a nice comfortable temperature. I also closed the exterior blinds and had the ceiling fan on low. Today that condition was met at 10:30AM and things also remained comfortable, though since there was plenty of sun I also turned on the bedroom AC unit and lowered them both to 22°C to see how that felt.

Speaking of sun… it was a nice clear day and the generation from my solar panels was the stereotypical ideal curve:

Consumption items of note are:

• hot water running for an hour from 9AM
• spikes at 10:30AM when I cooked an early lunch
• increasing usage with the AC at 24°C and then further increase when both running at 22°C
• spikes in early afternoon when I use the washing machine
• a drop at 5PM when I switched back to one AC at 24°C

It is nice that most of this usage is covered by solar generation. The stats for the day so far are:

• 29.6kWh solar generation
• 15.2kWh consumed
• 4.2kWh pulled from the grid
• 18.5kWh fed to the grid

The reconfiguration of my account for solar finally got done a week ago, so now I am getting credit for what I feed back to the grid. For this day at my current rates the consumption balances the feed-in, making the cost just the daily supply charge. However this is just one day and it is the impact over time that is more important.

I also noticed something odd when looking at the generation from the inverters on each of the solar panels:

So ten of the panels are generating as you would expect for a clear sunny day. But what is up with the other two? In the enphase app the panels are laid out over an aerial image of my roof and I could see that the two panels with slightly lower generation are the two that are next to my tv antenna. So the slight shadow that casts is affecting those panels, changing from one to the other as the shadow changes. While I don’t watch free to air tv often, I won’t get rid of the antenna as there are a couple of shows I still automatically record to watch later.

It has now been one month since I had solar panels installed and I am still working out what I want to monitor and how it will change my behaviour.

So what does the monitoring look like?

The cloud based monitoring that the Envoy controller reports to gives a status page, but I find the energy reporting to be more interesting. This is the report for yesterday:

There were clouds a couple of times but otherwise it was sunny, so there is a nice curve to the solar production. On the consumption side you can see there at 10am the hot water was on for an hour, then I was cooking lunch with my air fryer at 11:30am. It was a warm day so in the afternoon I turned on the air conditioning to keep things cool.

With the integration into Home Assistant I can get a similar view of the same data through the energy dashboard, though not as granular as it is in one hour (instead of 15 minute) increments:

This is getting its data from the “energy production/consumption today” values which are in kWh and reset each day. If I want live information I look at the power values which I have converted to W to be in line with what I get directly from the smart meter, from my UPS and from my tamsota devices. The same day but the power reading which is updated every minute looks like:

It starts to get messy but I can also include the power reading data from the smart meter (updated every 8 seconds):

If the smart meter reading is positive then I am consuming from the grid, while if it is negative then I am feeding power back to the grid. Of course I am still waiting for my meter/account to be reconfigured so I get paid for what I export…

It is clear that on a sunny day in summer that my solar generation will easily cover the large loads such as hot water, dishwasher, washing machine and lunchtime cooking. What would the numbers look like on my bill?

Not as much of a saving as I expected, but this is only a single day and I was running both AC units as an experiment while I would ideally just be running the one in my study. Definitely need to wait and see how the numbers fall for a full monthly billing cycle…

It has been two months since I started to think more about my energy usage and now my energy profile has completely changed. Two weeks ago the air conditioning units were installed, but I have not yet mentioned that yesterday I had solar panels installed and today they completed the install of a heat pump hot water system.

The shape of my roof is not the easiest for solar panels, but they managed to fit twelve panels facing north. The panels are each 370W while the microinverters are 295VA (see this video) which even on an overcast day should cover my typical usage. The system has been running for 24 hours now (technically I should now turn it off and wait for the inspection) and it has been interesting to watch how much they generate versus what the weather is doing.

I opted for microinverters from Enphase (the only option in Australia for microinverters) because I like the idea better than string inverters and the tipping point was that there is an integration included in Home Assistant. So while it is good to have the provided online interface, it was also nice to be able to easily add the solar system. Once added I had thirteen new devices. One for the Envoy which is the controller/gateway, and then each individual panel. The figures I will be interested in are the panel generation, my consumption and how much I feed back to the grid.

My first side quest was to figure out why my smart meter was now saying I was consuming an amount of power that was simply not possible:

As I worked my way through the source of this number I quickly spotted the problem. The number in the XML from the smart meter adapter is in hex and very large numbers start with lots of F. Thinking back to computer science subjects at uni I remembered that is likely a negative number if we are dealing with a signed integer. After some number conversion a demand value of 0xfffffc09 was now coming back as -1015 which is both sensible and aligned with what the Envoy said I was feeding back into the grid. As I had published the script for this to github, it was right to push a fix.

While there was still some daylight (and there was some generation from the panels) I then played around some more in Home Assistant, including enabling the energy dashboard, but that is going to be a longer term task.

As well as installing the solar system yesterday, the electricians also did their part of the install for the new heat pump hot water system. Ready for plumbers to come today to decomission the old hot water system in the roof (still working after 50+ years…) and hook up the new heat pump and storage tank. Its power usage would have been high today as it was heating up the entire tank but once things settle down I will try to record how much it needs day to day.

The piece missing from the hot water install is the wifi module, once they come back to install that I will have a new source of data. There is no out of the box integration as there was for the Envoy system, but I hope I can figure out a way to extract data.

However a much more immediate result is that I have now had the first shower in this house with mains pressure hot water, no more low pressure due to the gravity fed system…

I have recently learned two things about the halogen downlights I have in my kitchen.

First is how much power they use. While I do not have a direct measurement like I have for my dishwasher or washing machine, by watching the demand figure from my smart meter (updated every 8 seconds or so) I was able to confirm that they use 300W. This makes sense because there are six of them and they are rated for 50W each.

The second was that after almost 13 years I noticed that from my backyard I could see light in my roofspace through gaps in the tiles. Opening up the access hatch in the laundry I was able to confirm that a decent amount of light was coming from the back of the halogen fittings.

So they use a lot of power, light up the roof unnecessarily and probably get quite hot. It is also time to replace these with LED versions.

However this is proving to be not as simple as I hoped. These are 12V globes and when I tried replacing them with LED versions the lights come on but immediately turn off. The typical reason for this being that the drivers are not compatible. I think I need to replace the whole fixture with an LED version, there are few options at different price points, but all are around 8 to 10W. These days I much prefer 60W to 300W

I have a short (but growing) list of tasks for an electrician, this is now on that list.

As I have been working through the cost of my electricity and the specific costs for hot water and other appliances I have also been reading up on what it would mean to get solar panels. A great starting point is Solar 101: A Guide To Buying Solar Power Systems and I have been getting information from other sites as well.

I am in the process of getting quotes and one thing common issue is that the shape of my roof isn’t the best. I might not be able to fit that many panels on the north facing section, nothing faces east, very little faces west, and then there is a nice big south facing section. I would definitely get 4.4kW of panels facing north and then optionally a second set facing south. Or even have a second set on the flat roof of my detached garage, but first I need to completely redo that old roof.

One aspect that caught my eye is whether or not a particular load can be completely handled by solar generation. Paying 22c/kWh overnight for power and then getting back 6c/kWh for unused solar during the day, means you are still paying out 16c/kWh. That cost would instead be zero if it were able to be moved to be during the day.

I have four large electrical loads, how easily would they fit within 4.4kW?

1. heat-pump hot water

I plan to leave a heat-pump hot water system on the typical schedule of 10am to 4pm, but in practice I expect it will from from 10am for at most two hours, drawing a constant 1kW for that time. In summer this should be trivial for any solar installation, and hopefully be possible in winter, but there are those cold dark and wet days…

2. dishwasher

Based on the usage I have been tracking so far a typical cycle of my dishwasher will consume around 1.1kWh, but spread over an hour and a half with sustained peaks of 2kW (not this is around 8.5A, so under the 10A rating of the cable, plugs, etc) which makes sense as it needs hot water for both the washing and then the rinsing. Again in summer this should be trivial to run when there is ample solar, then in winter the solution might be to run it in the afternoon when the sun is highest and the hot water has finished.

3. washing machine

I was surprised to see that the washing machine also consumed around 1.1kWh like the dishwasher, but as I showed in the previous post the pattern is quite different, with it running for much longer and only heating up the water (also at 2kW) in the early phases. Unlike the dishwasher that uses hot water for rinsing, the washing machine uses cold water for that. These differences aside I would treat this the same as the dishwasher and run it in the afternoon and not at the same time as each other.

4. reverse cycle heating and cooling

This one is still the most unknown to me as I don’t have it and I cannot compare it against my current gas central heating. I do know when the gas heating has been running and I know when I would like to have cooling:

• Summer: Cooling to take the edge of the hot days and to make the really hot days livable
• Autumn and spring: Heating in the early morning (I start working from home at 7AM) and late evening
• Winter: Heating all though the day from early morning until late evening

The power usage for this system is hard to determine. For one model of system that I have been quoted the energy rating label says that for Melbourne it will use 920 kWh per year. How does that translate for my poorly insulated leaky house? This same model is rated at 3.5A when heating. So is that 0.8kW? I don’t yet know enough…

Do I need to know the detail now? Making these changes should mean that my overall grid consumption is lower so my monthly bills will be lower compared to my previous electricity and gas bills.

Something else I have realised is that the idea of running loads completely from solar means that I will be better off staying on a single rate plan instead of switching to a time of use plan. It doesn’t matter if the rate during the day is 22c/kWh or 19c/kWh if solar means neither is paid, but in the evening when there is no solar I would prefer to only pay 22c/kWh instead of 29c/kWh…

After working through the cost of heating water my next target of investigation was appliances.

I am going to consider a fridge (or also a standalone freezer) to be part of the background usage. It is an appliance that needs to run all the time and be reliable because I do not want spoiled food. I am not considering trying to control it, if it is using too much power then the option is to replace it with a newer more efficient model.

Some other large kitchen appliances are the oven and hotplate. I know how much power they use and I know that I mostly use them around lunchtime which is already in “off-peak” classification. The smaller kitchen appliances such as the toaster and microwave are not used on a regular basis so I am not going to worry about those. The dishwasher I will come back to later…

Appliances for entertainment such as the television and speakers are used for specific purposes. I should check their standby usage, but otherwise I am not concerned.

I know the computers and monitors in my study are a large portion of my regular power usage, but they are essential, either they need to be on because I am working from home, or they are on because I am using them for personal projects or entertainment.

So now we come to the washing machine and are back to the dishwasher. These two applicances have pumps or motors, but also heat water which takes a lot of energy. This has been in the back of my mind for a long time, so in order to find out I went to Bunnings and picked up a “smart plug” that also included energy monitoring.

It worked and I was able to get data into home assistant, but this device needed an account on a cloud service to be configured and then the home assistant integration hooked in via that. Not the self contained approach I prefer.

I have yet to return this plug to Bunnings, but I after seem a couple of mentions in forums and other loactions I did order two Athom plugs with AU sockets. Although I haven’t looked at Tasmota for a while I knew of it, and importantly I knew it was MQTT based which I liked.

It took a couple of days for them to arrive and I set one up for my dishwasher and other for my washing machine.

I estimate that I run the dishwasher every two or three days, and this is its power consumption on the “speed perfect” and “half load” setting:

These days with working from home I find that I am only doing a load of washing once a week for clothes, then a dedicated wash for sheets or towels. This is my washing machine on an “intensive” cycle which is what I use for towels:

Quite different patterns. You can definitely see when they are heating water, and I think the irregularity with the washing machine is due to how it is detecting the motor usage, compared to a pump in the dishwasher.

But what does this tell me? Not really much…

But what might I be able to do with this information? Maybe something…

One thing I can do for both appliances is turn off the power using the smart plug to eliminate any standby power usage. I could also use a schedule in home assistant to enforce the time of use, not allowing them to run at certain times of day.

Depending on how fancy I want to get (simple could be x watts used for more than y minutes) I should also be able to add some form of indicator to know if the appliance is or has been running. If for some reason I have started a load of dishes in the afternoon I don’t want to always kill the power at 3pm, I would want it to complete the cycle and then turn off the power. A more useful automation I could configure is an alert to tell me (and remind me) when the washing machine has finished, because while dishes are ok to be left in the dishwasher, damp clothes in the washing machine need to be taken out and hung up.

As usual with these things, as soon as I dig into one aspect a bit I being up more questions and possibilities…

As mentioned in my previous post about electricity usage I now need to talk about how I get hot water.

My current system is as electric system up in my roof which is set up as a controlled load. This means that it is on a dedicated circuit that my meter will only power from 11pm until 8am at a reduced rate. It doesn’t appear to have ever been replaced, which would make it 54 years old…

The usage varies from day to day, but an average for a month is 200kWh, which at my current rate means I pay around $35 per month. On its own that isn’t a huge figure, but small things do add up over time.

My current system is electric resistance, however the future is in heat pumps. There are two brands available to me that get excellent reviews and those are Sanden and Reclaim, these also happen to be the most expensive options. I found it interesting that these are not an all-in-one unit like the cheaper options, but are a split system with a heating unit and separate tank, for my needs I will opt for the smallest tank at 160L.

So how do these compare for electricity consumption? It is hard to predict but there are many claims of up to four times more efficient. For my comparison I am going to be conservative and use two times as efficient, so 100kWh over the month instead of 200kWh.

A heat pump is about moving heat, so while they can still heat the water when it is cold outside, they are more efficient the hotter it is as there is less of a differential. So instead of heating the water overnight when it is coldest, it makes sense to run during the warmer day, eg between 10am and 4pm which is usually what they are set to.

So what does high efficiency and a different time of day mean for me?

So even with the higher rate compared to the controlled rate, the lower consumption easily covers the difference. Remember that I am being conservative with this estimate, so the actual results should be even better.

I am going to try to put monitoring in place so I can see how it performs, especially at the extremes of a 10°C day in winter versus a 35°C day in summer…

Update 13 November 2023:

After reading/watching some more posts/videos from people with heat pumps (such as Reclaim Heat Pump Hot Water Solar Energy Usage UPDATE – EEVblog2) I am thinking that my estimate above is way too conservative.

Both the Sanden and Reclaim systems are stated to draw at most 1kW when in use, and extrapolating from other people’s reporting that should mean it would run for an hour a day to heat up my water. Over a month that would be around 30kWh, not the 100kWh I used above. So what does that do to the monthly costs?

Of course this is all still just a bunch of guesses, I won’t have any real data until I switch over, but the 1kW figure for the load does figure into thoughts on solar generation…

Continuing my thinking about how I heat and cool things in my house I have given my electricty bills the same treatment that I gave to my gas bills and produced another glorious Excel chart:

I have what is referred to as a “controlled load” which is that my electric hot water is on a dedicated circuit that only runs overnight (typically from 11pm until 8am) for a lower rate. I think I can see that there was a time when the consumption was fairly evenly split between hot water and everything else, but then once I started working from home the controlled load dropped a bit while the peak usage jumped up a fair amount.

I didn’t dwell too much on this data because there is a different data set that is much more detailed. If I want extreme detail I could go to the log of what I get directly from my smart meter, but an instantaneous power figure every eight seconds is a lot, and it only reports the peak usage, it doesn’t (though it did originally) report the controlled load.

The other data set I am referring to is the one that I can get from my electricity distributor as that is in a format of half hour blocks, essentially what the electricity retailer uses to calculate bills. Importantly this does include two sets, one for the peak usage and another for the controlled load.

I looked at this data in a few different ways but in the end summed up the half hour blocks for an entire month, this is for October 2023:

(Note that the peak and off-peak distinction is not real, I split them in the chart for something I will explain below, they are both currently billed as the same peak rate)

You can clearly see the controlled load turning on at 11pm to start heating up the hot water, then it drops off throughout the night as the amount of water that needs heating each day is different. Not sure what the bump around 5pm is caused by.

Looking at the peak usage there is a baseline visible overnight, then usage increases as I start working from home, a spike at lunchtime when I cook, followed by afternoon and then evening usage. There is no spike for dinner because that is just reheating the other half of the Hello Fresh meal that I cooked for lunch.

I was able to apply my current rates to this data and end up with the same amount as my bill for that month.

Another plan my electricity retailer offers is a time of use plan, where the usage is split into peak being 3pm to 9pm and then off-peak being 9pm until 3pm. The controlled load is still separate from this.

These rates are currently:

I have the data, so what if I calculated the cost of these plans against my past usage?

So there would be a slight benefit to switching to the time of use plan.

I haven’t been tracking the usage, but I think I do usually run the dishwasher and washing machine in the evening. It doesn’t make a difference while on the single rate plan, but that could be a big change if on time of use. For this I will find some plug in power meters that can report to Home Assistant (ideally MQTT based) so I can track it.

There are also some other options with other electricty retailers with a number of them offering three rates:

• Peak – 3pm to 9pm
• Off-Peak – 10am to 3pm
• Shoulder – all other times

Then there is a retailer such as Amber which gives a half-hourly rate that is based on the live wholesale rate. I don’t know if any others that do this, and this is where you don’t want to just run loads like washing in off-peak, but automate it so that it runs when the live rate is low. I’m not at that point yet, but maybe someday.

Some other things I haven’t covered in this post are the impact of switching to heat pump hot water, running air conditioning all year round, and installing solar panels…

Continuing my thoughts on the cost of heating I have been running through different ways of thinking about what my house is and what I would want in regard to heating and cooling.

So what is my home?

• A two bedroom unit that was built in 1970.
• Insulation in the ceiling, but not in the best condition and should be replaced. No insulation in the walls or floor.
• No windows facing east so don’t get any morning sun.
• My lounge has north facing windows, but no significant heat comes from those.
• Both bedrooms have west facing windows (so they get the hot afternoon sun)
• The bedroom I use as my study had a north facing brick wall that heats up in summer.

What do I have for heating and cooling?

• Gas central heating.
• One bedroom has an ancient in-wall air conditioner that I never use.
• Ceiling fans in the bedrooms and lounge.
• Venetian blinds on all the windows.
• External blinds on the west facing windows.

What is a day like in winter?

• It is cold and dark outside.
• Central heating warms everything up quickly.
• I have the heating first set to 16°C to help me wake up, then warmer for the remainder of the day.
• It is comfortable to work in my study or be in other rooms.
• The afternoon the sun might hit my study window enough that I will close the venetian blinds.
• Once the heating turns off it looses head fairly quickly, but I am asleep by then.

What about in the peak of summer?

• It is more variable, often overnight in the teens and mid to high twenties during the day, but then periods of hot weather were is is above 30°C at night and over 40°C during the day.
• Most of the time it can be comfortable with the external blinds to blocking the sun and then the ceiling fans circulating air.
• When it gets hot then everything starts to heat up and then stays hot for a day once the cool change eventually comes through. It did get to 40°C in my study once, but it is hard to work in anything above 30°C

For now I am setting aside the issue of insulation and keeping my focus on active heating/cooling as that has a much more tangible impact in the form of bills. I would like to insulate the walls and re-insulate the ceiling, but that will be long term.

Something I have tried when the house is hot and a cool change has arrived is to open up doors and windows to try and get a draught, but that has never worked very well. The idea of a whole house fan has intrigued me, but while a thing in places like the US, it is rare in Australia. A couple of companies do install them, but none I have found in Melbourne.

So what I am after is a way to make things comfortable throughout winter (such as heating the study to 20ish degrees while I am working), and then make the extremes in summer tolerable (getting from the high 30s to the mid to high 20s).

While ducted air conditioning would be nice as it would be unobtrusive (unlike the the indoor head of a split system), the additional cost (double, quadruple, or more…) is not as appealing. It would also be heating/cooling rooms that I am not spending time in, so without better insulation that would be a wasted running cost.

This line of thought is taking me to split systems which would have the advantage of being able to cool the specific rooms that need it AND the room that I wish to use at the time. While there is more it learn about these specifically, it is also bringing me back to electricity, when does it get used, how efficiently is it being used, and where does it come from?

More electricity used during the day means that solar panels will be more beneficial…

Procrastination had its hand in it, but as previously indicated I have gone through my gas bills to produce this masterpiece of an Excel 2003 chart:

For 2018 and 2019 I was commuting to the city for work so the heating would only run on weekday afternoons and evenings and then all day on the weekends. There is a noticeable step up in usage for 2020 onwards when I was working from home because now the heating was running during the day on weekdays as well.

It was also interesting to see that the usage over summer didn’t drop to zero like it used to. I put this down to there still being cold mornings fairly late in spring and early in autumn. Previously I would have gotten up and left for work without running the heating, but when working from home the heating would run to eliminate the morning chill even though by lunchtime it had warmed up outside.

Also note the constant blue line that is the daily charge. This is just under $1 per day, so $365 per year and I could only expect that to go up.

Looking at these numbers from a yearly perspective:

It is appealing to think that I could get rid of this ongoing cost. But what is the upfront cost of a replacement system and what is the ongoing cost of that new system?

I’m pretty sure that a replacement system would be a form of reverse cycle air conditioning. A drop in replacement that used the existing ductwork would be convenient, but that does not exist. It does look like there are options for a ducted system that would be installed in the roof with an exterior unit, but that seems rare and expensive. The cheapest and most varied option appears to be split systems (though I would prefer not to have something sticking out of the wall), with multi-split systems (one exterior unit running multiple indoor units) somewhere in between.

What would this cost to heat my house (or just the single room I am in) over winter? How much of that could be covered by the output of solar panels on those dark and cold days? As usual I have answered some questions but raised more…

It has been almost ten years since I started monitoring my home power usage from my smart meter. Since then I have improved how I do that and I also track the usage of my computers via a UPS.

Also hooked into Home Assistant is the control of my central heating, this has been working well and I have been comfortable (especially while working from home) but recent price increases have highlighted that it would be a good idea for things to change.

I get a gas bill every two months with the last one being $580 and the one before that $520. These are over winter when the heating is used the most, so I expect the next bill should be around $550. I checked my bills from last year and while the gas consumption is similar, they were around $180 cheaper. That is a big increase that I don’t like. I need to dig into things further, looking back over all my bills for the last couple of years, including from before I started working from home.

Once I have the information what am I going to do with it? There won’t be much I can do about the increasing prices so what can I do to reduce consumption? Getting around to replacing/upgrading insulation and similar changes could reduce the consumption, but what about eliminating my gas connection completely? Is it finally time to get reverse cycle air conditioning and use that for heating? That heating is during the day, so it is also time to get solar panels? What about my hot water, where are we up to with using heat pumps for hot water?

Lots of questions… as I get answers I will try to write them up.

I have written before about how I use a Zigbee dongle (the now discontinued RAVEn from Rainforest Automation) to get power consumption information from my smart meter. A bit over two years ago I also wrote about how it appeared that a failing power supply was interfering with the Zigbee connection and also confusing my UPS.

I think that my logic still holds for the UPS issues, but now I think I was wrong about it interfering with Zigbee…

Things improved when I rewrote my script to use a proper serial port library and then improved even more when I started to use that library correctly. However recently I noticed that there were still some gaps appearing in the power usage data, so I had another look.

My first action was to further cleanup my script so it both made more sense and to also report on more messages. I was only caring about InstantaneousDemand which is sent every 8 seconds, but it also often sends CurrentSummationDelivered and ConnectionStatus which I was ignoring.

Once I started logging ConnectionStatus I thought I might be seeing a pattern. At the times (for an hour or so every few days) that I stopped getting InstantaneousDemand messages, all that it was getting were ConnectionStatus messages, and the LinkStrength values were around 60 or 70, not the 100 it normally way.

So was something still interfering?

I couldn’t spot a regular pattern in the dropouts so I had no idea what possible interference there might be. The information about the RAVEn and other smart meter in-home displays mentions that placement of the device is important as Zigbee is low power. I had the RAVEn plugged into the back of my linux box which placed it about 10 metres from the smart meter with walls, furniture and the metal case in between. So what if I simply moved the RAVEn closer?

I had a long USB extension cable so it didn’t take long to relocate the RAVEn to be about 4 metres closer and not directly behind a metal box. After a week in this position I found that there was still the occasional reconnection, but nothing like the hours of no InstantaneousDemand messages that I was seeing before.

I could have just left the USB extension cable in place, but I didn’t like how it looked and didn’t want to add it to the mess of cables under the desk.

The RAVEn is a USB device that provides a USB serial port, on that port are XML messages. My script takes those XML messages and writes them to MQTT as JSON. Is there something else that I could plug the RAVEn into to do this, something that I can place close to the smart meter?

I’m a fan of using ESP8266 devices in the D1 mini form factor for my current home automation. Could I use one of these to build a RAVEn to MQTT bridge over wifi? Maybe, but with some caveats and possibly some effort and delay waiting for parts.

Other Arduino based options seemed just has hard so I turned to the old Raspberry Pi I had sitting around. I had previously used this to test out Kodi so I instead loaded up Raspberry Pi OS Lite and quickly found that I could transfer my existing perl script over, tweak it a little bit, and have it working.

The next hurdle with this as a solution was that it used wired ethernet and I don’t have wired ethernet in the room near the smart meter, I would need wifi if I wanted to have the RAVEn as close as possible.

What would it take to add wifi to this Pi? A USB wifi adapter can be used, but which one and how much would that cost? Would a cheap $8 adapter work, or would I have to get a $50 adapter? As well as not working, it might take a while for a cheap adapter to be delivered.

What about a newer Pi that included wifi? The Pi 3 B+ that I am using for Kodi has wifi even though I am using it on a wired connection, but that also costs towards the $60 mark, and seems to be out of stock.

Hold on, what about a Pi 3 model A+? This is smaller and cheaper than a B+, it also has wifi and the single USB port is fine for my single RAVEn. An online order and a few days later it arrived and was quick to get functional:

I needed a case for protection and liked the exposed look of the slim case from Core Electronics.

This has been running like this for about 36 hours now, taped the wall which puts it about 1 metre from the actual smart meter. Time will tell if this solves the reliabilty issues, but it is looking promising.

Of course this does seem like a bit of an overkill to use a whole Pi for this simple task. I might consider a Pi Zero, but I would need the W version (for wifi) and when you include the USB OTG cable the price is getting closer to that of the A+, and these are sold out everywhere I checked…

The final thing I want to mention today is that after I cleaned up my script I also wrote up some documentation and pushed it up to GitHub:

• popcorncx/raven-mqtt: Takes the XML messages from a RAVEn and writes them to MQTT

Just don’t yet look at my other repos as all you will see are two that were created seven years ago, only one of which has any code pushed to it. One of the items buried on my todo list is to clean up and push some of the other things I have written for my home automation setup…

Up until yesterday the last change I made to my script that pulls usage information from my smart meter was to make it use a serial port library. At the time I grabbed the example and apart from adding in a hack to remove the null characters I was getting it worked fine.

Inspired by some things at LCA2020 last week I decided that I would change how I was getting the usage data.

The adapter I am using appears as a serial port and while you can send commands, if you just read from the serial port it will output an InstantaneousDemand XML payload every few seconds. The script I was using would connect to the serial port and read until it got one of these payloads (erroring if it didn’t see one in 30 seconds), writing the data to MQTT for Home Assistant to pick up.

This didn’t seem to be the best way, it sometimes wasn’t able to open or read from the serial port (one hung process could give hours of errors) and it was also skipping over information.

My replacement version would instead run as a daemon, connecting to the serial port once and then publishing MQTT messages whenever an InstantaneousDemand payload appears on the serial port. I still had it die if no payload had been seen for 30 seconds, but it would be restarted as I set it up as a service.

This was working quite nicely for a few hours, but then I noticed the load value was high, checking with top I found that this process was taking 100% of CPU. This wasn’t right…

Upon checking the documentation for Device::SerialPort I found that while I had used examples from the SYNOPSIS section, there was a full EXAMPLE that was much better.

• In my loop I was trying to read() a single byte each time, instead I should be reading more bytes. The example used 255, so I went with that.
• I wasn’t checking the count of bytes returned from read(), this explained the null data I had been seeing. I was reading when no data was available, if the count was zero there was no data.
• There is a timeout value that controls how long the read will wait before returning zero data. If not set then the loop in my code would be calling read() as fast as it could, setting this to one second meant it was handled within the serial port library.

After making these small changes (aka using the library correctly) the CPU usage of this process dropped to nothing. While it wasn’t actually impacting the performance, it is good to do things properly.

Something else I an trying with this process is setting an MQTT Last Will and Testament message. This is a message that you set up when connecting to your MQTT server, but it will only get sent if there is an ungraceful disconnect. Coupled with a startup message I can get a notification when the process is starting and a notification if the process crashes. Time will tell how useful this will be, but it is interesting to learn about.

Power and internet comes into my home above my bedroom window. There have been a few times I have been laying in bed watching the cables whip around in the wind, wondering what damage that could be causing and how long the cables should last. This has in part been answered for me as the power cable (likely from when this place was built around fifty years ago) has now been replaced.

Tonight’s events possibly started around 8PM when I started to make some dinner, with one thing on the stove I started another in the microwave, at which point the kitchen lights dimmed (more than ever before) and in my study the UPS started to beep. For a while I had been tracking under voltage in my power because often the UPS would be boosting from battery, this time the voltage had dropped enough that the UPS was still able to boost, but also wanted to start shutting things down. Luckily I was done with the stove and microwave, once they were off the voltage was back to ok levels and the UPS was happy.

After I ate my dinner I started to check my logs and research who to contact about this, then my phone rang. It was my neighbour from the other unit asking if my power was on, because hers was not. This was unexpected as our units are semi-detached, we share the same power cable and the meters are in the same box. But then my power also went out.

Heading outside to talk we saw that the streetlights were on and that other houses in the street still had power. In the meter box I saw that both of our meters were on, so had our power been turned off remotely?

United Energy is my electricity distributor, nothing was listed on their outage page and as I was looking for a faults number to call I received a call. It was someone from United Energy to tell me that my power had been switched off as they had detected a fault. They asked some questions around if I had noticed any issues (I said I had) and told me that a work crew had already been requested and should be there some time that evening.

About an hour later the crew arrived, two people, one in a van and the other in a bucket truck. There were not the friendliest of people (they did have a job to do after all) but from what I could gather they identified the cable as old so would be the likely issue. An hour later they had replaced the cable and run some tests, my power was now back on and they were gone.

I mentioned that I was checking my logs, so what logs do I have?

After I resolved the issue of my UPS shutting down every few weeks I noticed that something was happening to cause the fans in the UPS to come on. The UPS is connected via USB to my linux box but all I was logging was the power output every five minutes. Adding the UPS component into Home Assistant gave me a nice view (and history) of a number of values:

I set up an automation to notify me (via Pushover) whenever the status changed. Over time I was able to see that the UPS was detecting a drop in input voltage, so was using the batteries to boost back up to a normal level. This would typically happen if I used two large applicances at the same time (eg washing machine and stove), but also at other times as well. It was on my todo list to find out what the acceptable voltage range was and probably get it looked at.

So what was the voltage doing tonight? This:

A few things can be seen:

• Around 230V before 5PM when I wasn’t home
• Initial drop to around 210V as I put my hot water on boost, then sitting around 220V
• Big drop to 200V and then as low as 180V around 8PM
• No data when the power was off
• Back to 233-239V once I turned everything back on

I will continue to monitor the UPS status with the expectation that I should not (or at least rarely) get notified about undervoltage again.

The final thing I want to say now is that this has been an interesting coincidence. The reason I needed to boost my hot water was because it had been turned off all week while I was at LCA2020 where the overall theme was security and privacy. The specific coincidence I am thinking of is that there was one talk about the smart meters (I hadn’t realised that outside Victoria the rollout was still ongoing and contentious) and I was part of a couple of discussions about their advantages and disadvantages. In this case the remote detection of a fault and quick rectification was a good thing.

We know when you are sleeping: The Rise of Energy Smart Meters – Rachel Bunder (LCA 2020)

Many years ago I started monitoring the power consumption of my house via a ZigBee dongle that communicates with my smart meter. The quick and dirty solution I did at the time stayed in place for a long time, until it started to play up…

The first symptom I noticed was that my script would hang, in itself not that bad, except that I was calling it directly from MRTG… which would cause the entire MRTG polling loop to hang, so I wouldn’t get any monitoring. In response I split the script, one to read the usage to write to a log, and another (called by MRTG) to read the latest entry in the log.

The reading script would still get stuck, so I added a generous timeout and stopped thinking about it. Until I thought it would be a good idea to also drop the usage data onto MQTT for Home Assistant to grab. Nothing wrong with this, except that I upped the frequency from once every five minutes to every minute. Sometimes it would fail for hours, sending an email with the error every minute…

I initially noticed the increase in timeouts around the same time that I upgraded the hardware in my linux box and did a fresh install of Ubuntu. Due to default permission changes I found that I could no longer simply cat the serial port, I needed to connect using Device::SerialPort, so I was thinking that there was something wrong with the usb-serial chipset or the driver.

That was until a few weeks ago, when I upgraded the hardware in my Windows desktop.

For a long time I have been aware of a slight ticking sound coming from that computer, you know the sound of a fan slightly hitting something or being slightly off balance?

The new build went great and although I didn’t really need the upgrade it let me do an upgrade that was required, to my parent’s computer. As I was handing down parts I thought that I could replace the power supply fan instead of buying a whole new power supply, so I powered it up and heard the same noise…

… coming through my speakers.

Oh, this is not a bad fan, this is a failing power supply.

So what does serial port problems in one computer have to do with a bad power supply in another one? Probably nothing, but since replacing that power supply I haven’t had a single timeout error, it is as stable as when I first picked up the adapter. I guess it is possible that the power supply was generating interference at around 2.4GHz…

Another thing I didn’t think was related was that the UPS that these two computers run from had started to shut down. Not in any graceful manner, but with a sudden power off followed by a loud continuous beep. I suppose it is also possible that a bad power supply could also trip the UPS…

While some people are heavily against smart meters, I am not concerned. In fact when I received the initial notification about the installation my first thought was about the possibility of playing with new technology.

When they finally installed the meter it coincided with a co-worker getting solar panels installed which led to a number of conversations about ways to monitor power generation and consumption. Based upon previous research I had done I knew that other people in Melbourne had had success with Rainforest Automation devices which use the ZigBee Smart Energy wireless protocol to connect to the smart meter.

My co-worker opted for the EAGLE as his solar panels also connected over ethernet, while I opted for the (cheaper) RAVEn which is a USB dongle.

Once the devices arrived I had to wait a few more days until my smart meter was completely setup, but then it was a simple matter of entering the address and install code from the RAVEn into the online portal for the smart meter. After a quick test with the windows app, I plugged it into my Linux box to see it come up as a serial port.

It was nice to simply run cat /dev/ttyUSB1 and see it output an XML fragment reporting the instantaneous demand every few seconds.

The documentation for the XML API showed me how to send commands and how to convert the hex values to decimal and how to apply the multiplier and divisor. It didn’t take long to wrap this in a script to be called by MRTG:

Events visible in this sample include:

• Hot water turning on at 11PM AEST and topping up a couple of times
• Fan and light while getting ready for work
• Fridge cycling on during the day
• Use of oven to cook dinner
• Lights and other usage when I am at home

Due to complications with having off-peak electric hot water (aka a ‘controlled load’) I do not get summation values, instead that is just a graph of the instantaneous load. So while it doesn’t give true usage, it is a good enough indicator.

Currently this graph is available to anyone who knows the URL, and while it can let someone determine when I am or am not at home, the easier way to do that would be to go into my backyard and look through a window.