Gas usage and its cost

Friday, October 20th, 2023 at 09:09pm

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:

YearTotal UsageDaily ChargeUsage Cost
201827582 MJ$301$567
201930074 MJ$326$645
202052402 MJ$326$981
202156883 MJ$328$896
202258485 MJ$333$1010
2023 (partial)44669 MJ$231$1156
2023 (estimated)60000 MJ$354$1500

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…

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