Halving our electricity usage

I learnt something interesting today: between 2007 and 2011, we halved the amount of electricity we use in our house:


In 2007, we used 6783 kWh of electricity (for electricity, a kilowatt hour is the same thing as a ‘unit’ on your bill). In 2011, by contrast, we used 3332 kWh (or ‘units’). 2007 was slightly on the high side (compared with 2006) because we had no gas fire in the living-room during the winter of 2006-7 so we’d used an electric oil heater during the coldest weeks (we don’t have central heating in that room) 1.

That’s an average of 19 kWh per day in 2007 compared with 9 kWh per day in 2011. Which is quite a difference. So what changed?

In early 2008, I got a plug-in Maplin meter (similar to this one) and one of the very early Current Cost monitors, which display in real-time how much electricity is being used in your whole house:

Current Cost monitor

Aside from the fun of seeing the display numbers shoot up when we switched the kettle on, it informed us more usefully that when we went to bed at night or out to work, our house was still using about 350 Watts (which is 3066 kWh per year)2 of electricity. That’s when the house is pretty much doing nothing. Nothing, that is, apart from powering:

  • Fridge
  • Freezer
  • Boiler (gas combi boiler with an electricity supply)
  • Hob controls and clock
  • Microwave clock
  • Infrared outside light sensor
  • Print/file server (basically a PC)
  • Wireless access point
  • Firewall and Internet router
  • DAB clock radio
  • ADSL modem
  • MythTV box (homemade digital video recorder; basically another PC)

And that’s the thing, this ‘baseline’ often makes a lot of difference to how much electricity a house uses overall. 3066 kWh per year was 56% of 2007’s total electricity usage.

The first six items on that list draw less than 100 Watts (876 kWh per year) altogether. They’re the things that we can’t really switch off. But there were clearly things that we could do something about.

Over the next couple of years, we reduced our baseline by about 100 Watts by getting rid of some of the excessive computer kit, buying more efficient versions when we replaced the old print/file server and MythTV box, and replaced most of our lightbulbs with energy-efficient equivalents. We also, importantly, changed our habits a bit and just got more careful about switching lights off when we weren’t using them (which wouldn’t affect the baseline but does affect the overall energy usage), and switching off, say, the stereo amplifier when we’re not using it.

That brought our baseline down to about 230 Watts (2015 kWh per year), which is a lot better, though it’s still relatively high considering that the ‘essentials’ (eg fridge and freezer) contribute less than half of that.

And that’s about where we are now. We tended to make changes in fits and starts but none of it has been that arduous. I don’t think we’re living much differently; just more efficiently.

1The complementary gas usage graph shows lower gas for that year for the same reason; I’ll blog about gas when I have a complete set of readings for 2011).
2350 Watts divided by 1000, then multiplied by 8760 hours in a year.
Photo of the Current Cost monitor was by Tristan Fearne.
Thanks also to @andysc for helping create the graph from meter readings on irregular dates.

7 thoughts on “Halving our electricity usage

  1. I rather wish I’d carried on grabbing our data at home. I had some problems with my low power server that sort of brought an end to it all and I’ve not bothered again since. However, this sort of long term view is a real motivator to keep going! Thanks for sharing.

  2. @Graham: I did this based purely on electricity bills (with estimated readings removed) averaged over days (because readings were on different days of the month and not year endings). So if you still have your old bills you’re fine.

  3. Well done Laura. It is clear that you are doing your bit for the planet. I have been collecting a lot of data on my electric usage, but so far I haven’t made much progress in bringing it down.

  4. Laura, this is a most commendable effort and quite inspiring. I wish I hadn’t jumped about energy suppliers so much (getting cashback via Quidco etc… then when it has cleared moving suppliers again so almost covering each quarters bill!). However, I am going to have a root about for my bills and try and do something similar as it is truly tangible evidence as to whether or not I apply my energy conservation know-how.

    Do you leave your set top box, router etc… on, what are your next plans for shaving off more from your kw/h usage, did you research energy efficiency gains when replacing your server and Mythbox TV set up and have you done a post on your TV set up (or offer sign-posting to useful info source)as I want to move away from blinking Virgin “rip off” Media and need to get gen’ed up on more efficient way to watch and record tv !


  5. @Alex: Tony (my other half) built the MythTV system and used to have the details online – he’s removed the link from his website though, and they might be out-of-date now. Basically, it’s a low-powered PC so it’s quiet in the living-room and it has a digital tuner thing to receive. MythTV is a Linux distribution which downloads the Radio Times XML feed every few days for scheduling recordings. We have live TV pausing etc. Pretty good. I’ve never used a commercial one so I don’t know how it compares or what else is available out there.

    Coincidentally, the server broke down last week so we’ve been looking into lower power replacements but actually it makes more sense to just fix it (if we can) at the moment. Which does mean it’ll still appear higher than I’d like on the graphs but it’s probably more sustainable overall to keep the old hardware going for another couple of years if possible. While the server was down, I tried turning off the router – I’ve not checked yet but it means I should be able to tell what it uses and what the server itself uses without having to unplug them once they’re working again.

    Instead of replacing the hardware, we’re thinking of looking into how to get the harddisks to spin down as that’s probably what takes a lot of the power. If we get anywhere, I’ll report back! 🙂

  6. I have Economy 7 in my apartment and I use the economy 7 hours to do all my washing and drying, cooking, heating water for 1 hour. In the winter months Economy 7 hours are 12am to 7am. I use all my heavy electric usage between 4.30am to 7am. I find this economical and my monthly DD is £59.00. I am already in credit for only two months supply. I have energy lights and only switch a light on in the room that I am using. The tie after 7am the only electric usage is for a mug of tea or coffee and heating my meal in the microwave. I think I have cracked the electricity economy in my apartment. If you have Economy 7 electricity use those hours to minimise your electric bill.

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