Tag Archives: energy

Reflecting on our total home energy usage

The graph of our total gas usage per year doesn’t decrease quite so impressively as our electricity graph, which I blogged about halving over five years. Because the numbers were getting ridiculously big and difficult to compare at a glance, I’ve re-created the electricity graph here in terms of our average daily electricity usage instead of our annual usage (click the graph to see a larger version):

Graph of daily electricity usage per year.

 

If you compare it with the average daily gas usage graph below, you can see (just from the scales of the y-axes) that we use much more gas than electricity (except in 2007, which was an anomalous year because we didn’t have a gas fire during the winter so we used a electric halogen heater instead):

 

Graph of daily gas usage per year.

Our gas usage has come down overall since 2005 (from 11280 kWh in 2005 to 8660 kWh in 2011; or 31 kWh per day to 24 kWh per day on average) but not so dramatically as our electricity usage has. Between 2005 and 2011, we reduced our electricity usage by about a half  and our gas usage by about a quarter.

Gas, in our house, is used only for heating rooms and water. So if I were to chart the average outside temperatures of each year, they’d probably track reasonably closely to our gas usage. In 2005 (when we used an average of 31 kWh per day), we still had our old back boiler (with a lovely 1970s gas fire attached) which our central heating installer reckoned was about 50% efficient. In 2006 (26 kWh per day), we replaced it with a new condensing boiler (apparently 95% efficient) but didn’t replace the gas fire until mid-2007 (the dodgy year that doesn’t really count). In 2006, we also had the living-room (our most heated room) extended so it had a much better insulated outside wall, door, and window. These changes could explain the pattern of reducing gas usage year by year up till then.

Old boiler being removed

In 2009, January saw sub-zero temperatures and it snowed in November and December. I think that must be the reason why our usage for the whole year shot back up again, despite the new boiler, to 31 kWh per day. In 2010 (21 kWh per day), it was again very cold and snowy in January; I think the slight dip in gas usage that year compared with both 2008 (25 kWh per day) and 2011 (24 kWh per day) was down to a problem with the gas fire that meant we used the electric halogen heater again during the coldest month. In 2011 it snowed in January but was fairly mild for the rest of the year.

I think 2008, 2010, and 2011 probably represent ‘typical’ years of heating our house with its new boiler and gas fire. Like I concluded about reducing our electricity usage, I think our gas usage went down mostly by getting some better insulation and a more efficient boiler but we did also reduce the default temperature of our heating thermostat to about 17 degrees C (instead of 20 degrees C) a couple of years ago too (we increase it when we need to but it stays low if we don’t), which I think has made some difference but it’s hard to tell when our heating usage is so closely tied to the outside temperature. Also, we don’t currently have any way of separating out our water heating from our central heating, and our gas fire from the boiler.

Of course, what really matters overall is the total amount of energy we use (that is, the gas and electricity numbers combined). So I’ve made a graph of that too. Now we’re talking numbers like 48 kWh per day in 2005 to 33 kWh per day in 2011.

 

Graph of total daily energy usage per year.

Overall, that means we reduced our total energy usage by about one-third over seven years.


Thanks again to @andysc for helping create the graph from meter readings on irregular dates.

Halving our electricity usage

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

electricity-graph-18thFeb2012

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.

UX hack at London Green Hackathon

At the London Green Hackathon a few weeks ago, the small team that had coalesced around our table (Alex, Alex, Andy, and me) had got to about 10pm on Saturday night without a good idea for a hack, in this case a piece of cool software relevant to the theme of sustainability. We were thinking about creating a UK version of the US-based Good Guide app using on their API to which we had access. The Good Guide rates products according to their social, environmental, and health impacts; the company makes this data available in an API, a format that programmers can use to write applications. Good Guide uses this API itself to produce a mobile app which consumers can use to scan barcodes of products to get information about them before purchase.

Discussing ideas
Discussing ideas

The problem is that the 60,000 products listed in the Good Guide are US brands. We guessed that some would be common to the UK though. We wondered if it would be possible to match the Good Guide list against the Amazon.co.uk product list so that we could look up the Good Guide information about those products at least. Unfortunately, when we (Andy) tried this, we discovered that Amazon uses non-standard product IDs in its site so it wasn’t possible to match the two product lists.

The equivalent of the Good Guide in the UK is The Good Shopping Guide, of which we had an old copy handy. The Good Shopping Guide is published each year as a paperback book which, while a nicely laid out read, isn’t that practical for carrying with you to refer to when shopping. We discovered that The Ethical Company (who produce the Good Shopping Guide) have also released an iPhone app of the book’s content but it hasn’t received especially good reviews; a viewing of the video tour of the app seems to reveal why.

Discussing ideas
Quite late at night

By this point it was getting on for midnight and the two coders in our team, Andy and Alex, had got distracted hacking a Kindle. Alex and I, therefore, decided to design the mobile app that we would’ve written had we (a) had access to the Good Shopping Guide API and (b) been able to write the code needed to develop the app.

While we didn’t have an actual software or hardware hack to present back at the end of the hackathon weekend, we were able to present our mockups which we called our ‘UX hack’ (a reference to the apparently poor user experience (UX) of the official Good Shopping Guide mobile app). Here are the mockups themselves, along with a summary of the various ideas our team had discussed throughout the first day of the hackathon: