Wednesday, 5 September 2012

How much power does your house use?

Average usage per day in KWh
Another interesting question for you all, in response to Anne's last post, and my general advocacy of monitoring.

How much power do you think your house uses when you think you've turned everything off you can? So, that's leaving fridges, freezers, computers you never turn off (I have an excuse, dear!), etc etc.

You don't know? You might be very surprised when you find out.

Our average daily usage in 2010 (as per the graph opposite) was around 18KWh, of which a sizeable amount was being contributed by stuff that was always on - old computers with inefficient power supplies can chew a couple of hundred watts, which is getting on for 5KWh over a day.

Stop for a moment, and think about that.

Scary, isn't it. One computer, probably 60p a day. Over £200 a year.

A very handy rule of thumb at
present: if you pay 12p a KWh,
it's accurate to within 5%.
Also: 1 KWh/day for a year = £40
Early in 2011, I finally decommissioned the last of the old servers (I'm an IT professional - I host several web sites and other things for friends, just to keep my hand in as a sysadmin) and replaced it all with a MiniITX box from the rather excellent, that eats, relatively speaking, next to nothing. Somewhere about then is when we started monitoring, and I think our quiescent usage is around about the 300W mark - or about £300 a year.

You'll notice our 2011 average is down to about 13KWh/day. Pretty much, just from doing that.

Our 2012 average is down to about 8.5KWh a day. Why? Actually, most of that's a no-brainer. Solar PV. As soon as the solar panels kick in, they start powering the house. Quite literally: once the sun gets out enough that the watts the PV is kicking out pass the magic 'things that are always on' point, we're running the basic functions of the house for free.

On top of that, our washer and dryer now have timers, so we can run them when the sun's out. And we have a new fridge to replace the 10+ year old one, that only uses about 150KWh a year (that's about 17W!).

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