What’s using electricity in our empty house?

As part of my Social Consumption Project, I’ve had an electricity meter reader logging our household usage to a database since late September.

The week of October 5 our house was empty – I was in the west coast and Catherine and Oliver were in Ontario – and so this gave us a great chance to find out what the base electric load of our house is when there’s nobody living in it. Here’s what we found (number are kWh per day from October 5 to October 11, 2014):

Electricity Usage, in kWh, at 100 Prince Street in October, 2014

Other than lights, we took no steps to turn things off during our absence – poor planning – and so the bulk of the consumption that week were things like the refrigerator, the “instant-on” appliances, like our TV set, and our iMac computer, which we left on (and which was used a couple of times a day by our friend G. who was checking the house for us).

Maritime Electric’s charge for electricity is 12.78 cents per kWh, so our electricity was costing us between 64 cents and and 77 cents a day. So we weren’t going broke. But that’s that’s still $5.00 that we didn’t, in theory, need to spend that week.

By comparison, here’s our electricity usage for this week, when the house was fully occupied:

We used 117 kWh this week, which is 79 kWh more than an empty house, which you could say is our “discretionary” electricity – the stuff we do deliberately by turning something on.

Which made me curious: that 38 kWh our house used the week we were away, the electricity the house uses when we don’t deliberately turn something on, what’s using that?

And so I borrowed an electronic energy meter from the Confederation Centre Public Library (almost every public library on Prince Edward Island has one, so this is easy for anyone to do, and it’s free) and this weekend Oliver and I measured the electricity consumption of everything in the house that plugs in.  Here’s a chart showing the “stuff that’s always on that uses electricity”:

Appliance Load
Refrigerator 30 watts
Mouse Repeller 3 watts
Television 4 watts
Nintendo Wii 8 watts
Stereo 11 watts
Eastlink Router 9 watts
Apple Airport Extreme 7 watts
VOIP Telephone Box 5 watts
iMac Computer 94 watts
TOTAL 171 watts

There are some other things that aren’t counted in that total – the furnace coming on, a light that’s always on in the upstairs bathroom – but that total covers almost everything.

And so our “idle” household uses almost as much electricity as a 200 watt light bulb left on all the time.

And, indeed, 171 watts per hour is 0.171 kWh and 0.171 kWh for 24 hours is 4.1 kWh, which is within 1 kWh to what my electricity meter readings showed (the difference was likely those things we didn’t count, plus some lights that G. would have used).

There are some things we can do to lower this base load, some of which I’ve already done:

  • I’ve moved the television, stereo and Wii to a power bar that I can shut completely off when we’re not using them: that will save us 23 watts of load, or about half a kWh per day if we never turned them on.
  • We could have the iMac go to sleep (rather than just “idling” with the display off); this could save about 2.25 kWh per day if we never turned the iMac on.

Of course if nobody at all was going to be using the house, we could also turn off the Internet gear and the phone and we’d save even more.

The other step we’ve taken is to start to replace incandescent and compact florescent light bulbs with LED bulbs, starting in the living room. So far I’ve replace 221 watts of load with 59 watts but replacing the bulbs in the three lamps we use most often.

It may seem absurd to be taking these seemingly minor steps that will save us a few dollars a month on our electricity bill at most. But these small things mean a lot on a province-wide level.

There are about 40,000 households in Prince Edward Island. If each of those households has a computer on all the time that consumes about 100 watts of electricity, that’s 4 millions watts of electricity being used to power all those computers; that’s 4 megawatts, or about 2% of the Island’s electricity load (193 MW) as I type this sentence. That’s a lot of electricity, and it’s electricity that we weren’t using a generation or two ago. It’s also electricity that we could save a lot of if we put our computers to sleep (or turned them off) when we’re not using them.


Ken's picture
Ken on November 24, 2014 - 16:41

Just think of all the office and school computers left on overnight. A campaign to halt that could use an app that logs the computer power state and has an icon that turns green to certify that it is 'power wise'. A contest could be organized based on the number of power smart certified computers used by schools, offices, or other orgs. The app would report each computers power profile back to a database.

Oliver Rukavina's picture
Oliver Rukavina on November 25, 2014 - 15:58

:( I am not a Pre-Historic Kid I am a modern kid

Clark's picture
Clark on November 26, 2014 - 19:49

I had no idea my iMac used 3x the amount of power as my refrigerator when idle.

Oliver B's picture
Oliver B on November 30, 2014 - 15:44

Are you replacing your CF bulbs before they've expired? I've been tempted, but when I think of the carbon cost of their manufacture and the difficulty of disposing of them, I've figured I should try to get the most of them--because LEDs don't improve on CFs as much as CFs improved over incandescents. I did retire a bunch of incandescents before they'd expired to replace them with CFs.

Peter Rukavina's picture
Peter Rukavina on November 30, 2014 - 19:31
The performance of the CFL bulbs is so poor in the winter – they take 10 minutes to get to full brightness – that I’m simply moving them to seldom-used places of the house, like the basement, replacing incandescent bulbs.
Oliver B's picture
Oliver B on November 30, 2014 - 22:01

Oh, yeah, I have some bulbs like that. I don't blame you.

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