When ‘off’ isn’t off

Tuesday, April 17th, 2007 at 8:40 pm

As part of the push to reduce energy usage at work we were able to borrow an energy meter so we could see first hand the usage of various appliances.

The most common LCD display we have is the HP 1702. At full brightness it uses 30.2W while at half brightness it uses 21.4W. These numbers are not that surprising, neither is the standby usage of 1.7W. What did surprise us is that when the screen is ‘off’ it still consumes 1.6W. The power needed to monitor the soft power switch is only slightly less than the power needed to watch for a video signal and to light the orange LED.

The other displays we have (HP 1740 and HP L1706) were similar with off/standby values of 1.0W/1.1W and 0.8W/0.9W.

So should we bother turning these displays off? The only way to have significantly less power consumption than putting them in standby is to switch them off (or unplug them since the points in the partitions do not have switches) at the power point.

Next week we should be able to borrow the meter for longer which means that some of us will be able to take it home for personal tests.

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