saving electricity at home

Saving electricity at home is all round a good thing to do. It saves money, it reduces your carbon footprint if you care about that sort of thing, and it cuts down on waste. What’s not to like?

For some reason the subject has been hijacked by two small changes that seem to capture  lots of column-inches but aren’t that effective in the grand scheme of things – changing your lightbulbs and unplugging your phone chargers when not in use. Sorry to rain on the green parade, but these aren’t the chief power hogs in most people’s homes. This is a straightforward engineering problem, one that is best tackled by measurement and the application of science, not mantras.

You need two tools for the job, one temporarily and the other is a nice to have to keep on top of things. It’s all down to Kipling’s serving-men, though we can stick with What, Where and When.

Tool #1 – Appliance consumption meter

This measures the amount of power used by an individual appliance- you plug it into the socket and plug the appliance into the meter’s socket. It’s nice to get one that measures the cumulative power used over a period, because to get an accurate idea of a fridge’s daily use you want to accumulate the consumption over a week and divide by 7. Most people have a different daily lifestyle on the weekend compared to the weekday, so capturing over a week gets information representative of all types of use.

Appliance consumption meter
Appliance consumption meter

Unfortunately you only need this temporarily while you’re in the Identify the Power Hog stage – they’re not horribly expensive but it’s worth trying to borrow one first. These are also not very accurate at low power consumption devices, such as mobile phone chargers. Presumably the stories about unplugging your chargers came from somebody at Greenpeace measuring a charger with something like this and seeing about 50W or so. If I saw a charger using 50W I would reach for a fire extinguisher. A bit of common sense is needed – a charger is about the same size as a old-skool light bulb. If it’s dissipating 50W, it will be getting about as hot as a light bulb, and anybody who has tried to change one of those that has just blown will know they are damned hot. If it were the phone dissipating the 50W rather than the charger I’d still be very afraid….

View the results for loads less than ~50W with suspicion. Fortunately that isn’t really a problem, you are after hunting the big game here, unless you’re already living off-grid. I was an early adopter, so I got taken for a ride when I bought mine for £20, people like Maplin sell these. You’ll get your money back in power saving unless you’re a hermit.

It’s the things that change temperature that are the power hogs. Hit these guys first, and preferably measure their power usage over a week to know what they are costing you.

Everybody knows electric heating is expensive – every kilowatt-hour in the UK costs you between 12 and 20p on a standard domestic rate. Three kilowatts is about the maximum you can draw from a standard UK power socket, and a typical fan heater is about 2kW. Use one of these suckers for 4 hours and the kWh is 2kW x 4 hours = 8kWh, which could set you back £1.60. If you’re a homeowner using electric heating then look at alternatives such as using a woodburning stove – almost any other fuel is cheaper per unit heat.

It’s hard to live without heating and changing the heat source usually demands capital spend. However, two other domestic energy hogs need to be tackled before the light bulbs –

Fridges/Freezers. These bad guys are on all the time, and worse still, their performance tends to deteriorate gradually over time. I had a Zanussi fridge freezer which was a few years old that drew over 4kWh a day, ie 1500 kWh a year. This punk was costing me £210 a year to run (@14p a unit on average). The one I replaced it with is A rated, and uses about 1.7kWh a day, a saving of ~£120 a year. That cost me £230 in October last year, so it has already paid me back about £100 in power costs this year, and by the end of next year I will have broken even. After that I am in extra time – what investment can you get that gives a 50% ROI year on year these days…

Tumble Dryer/Washing Machine

I was of the view that washing machines were power hogs but mine isn’t, it takes less than 1kWh for a wash. That’s pretty much over a cycle at 40deg  and it doesn’t matter how full it is. So fill it, but not so much the washing can’t move.

The tumble dryer, however, is another matter – it takes about 3kWh to dry a load of washing. There’s a free alternative that doesn’t take power, it’s called a washing line 🙂 Unfortunately this is a change in lifestyle, and not one for the better – hanging washing out is a right PITA. At least the weather forecast is better now so you can usually work out whether it’s going to rain and hence if it’s worth doing a wash in the morning.

The cost of using a tumble dryer is only about 40p a go, but it is a regular cost so like any regular cost it adds up over time. It also knackers your clothes, so the actual cost is probably more like 50p a go when that is taken into account.

Immersion Heater

These guys are such power hogs you can’t usually run them off a 13A plug, though that didn’t stop one landlord of mine doing that, and the plug did get mighty warm too. There are three things you can do here: get a timer, use less hot water, lag the tank as much as you can. if you have one it is worth getting a feel for how much it is drawing – even if you have to switch everything else in the house off and read the meter before you go to bed and then in the morning. When I did that I turned mine off and it stays off – I use my gas central heating on water only mode, it’s still cheaper than using one of these infernal devices.

Use a Whole House Monitor to keep Power Usage down

Once you’ve taken these high-power devices out or got them under control/started saving for efficient versions you can then start fiddling about with mobile phone chargers and light bulbs. There’s a nasty tendency for new things to get added to the background drain of your house, particularly it seems if you have children 🙂 That’s where you need a whole-house monitoring device, which clamps around the main live intake wire and sends the whole house usage. Mine is an Efergy monitor (I got rushed for that too, they’re now less than £50)

Efergy whole house monitor
Efergy whole house monitor

These allow you to keep an eye on total consumption. You soon get used to the background usage of your house with the fridge on and off (mine is 0.12kW and 0.04kW respectively). It’s good because before you go to work you take a look and if it says anything else you’ve left something on that doesn’t have to be on. And you get to see if it creeps up for any reason…

See -nary a word about light bulbs. What about them? My maximum wattage was 60W light bulbs, assume two of these are on all the time 6pm to 11:59 pm for half the year. That’s £18. That duff fridge freezer was costing me five times that much. Using a tumble dryer twice a week costs you twice as much. I can’t get excited about sweating the small stuff. Want to save money on lighting without spending a bean? Never underestimate the energy saving potential of the humble light switch set to the off position. Switch the buggers off when you’re not using them, just like your parents and mine did when electricity was more expensive in real terms….

So where did all this fuss get me then?

My power usage, cost and cost per unit
My power usage, cost and cost per unit

The dip in 2005 and the subsequent peak is an artifact of changing provider then. I got all this kit early 2008. One the one hand it is depressing, I’ve sweated hard to get my power bill back to a shade under where it was in 2003.

On the other hand, I’ve more than halved my power consumption, and the reason the bill is the same is because the cost of electricity has gone up more than two times in seven years. Look at the monotonic rise in the cost graph. This is because North Sea Gas is running out, it is because the Pound in falling, it is because there are lots more people in the world wanting a slice of a limited energy pie. I don’t expect it do come down any time real soon. So although in financial terms I’m not going anywhere, it is still worth doing, else I’d have to find another £500 a year. And personally, I’d rather consume that as decent red wine rather than making a donation to EDF’s slush fund…

There is a nasty little wrinkle in this – look at the unit prices charged:

Differential unit pricing hides the standing charge
Differential unit pricing hides the standing charge

A shade under half my usage is charged at higher rate, which is used to hide the quarterly standing charge of about £16, because most electricity consumers are not adult enough to be prepared to see the cost for the provision of service separately.  So it’s hidden as an extra unit cost for the first 240 units. EDF presumably think that nobody can get the quarterly consumption down below 240 kWh. Now I am half way there. If I could get the rest of the way, by taking over some of my demand by alternative means, or by say using a gas fridge, then I could get a much better marginal rate for energy saving 🙂

None of the steps taken so far  is anything that uses my specific knowledge of engineering, it is simply common sense that anybody can do. It means I don’t have to get uptight about my light bulbs or my mobile phone chargers, and indeed I still use incandescent light bulbs and a LED lamp for reading. In the future I may shift my lighting load to LEDs and renewables, more from a resilience/off-grid POV because I expect Britain to suffer power shortages as a result of a lack of capital investment in its generating capacity in the medium term future, and this sort of solution is specific to me. However, it won’t particularly change my power bill because I switch lights off if I am not using them.