Wednesday 30 July 2008

Tips to reduce your electricity bill

Things I learnt by using a CurrentCost meter

For the last month or so, my wife and I have been using a CurrentCost meter to track our electricity usage - with a view to helping the planet as well as the more direct benefit of reducing our electricity usage in the face of pending increased utility costs as part of the so-called "credit crunch".

The meters cost around £40 and have a small box that clips onto the wire by your electricity meter (no wiring necessary). This box wirelessly transmits the current power usage to a display unit which can be anywhere in the house (We have it in the kitchen so we see it regularly) and displays your current usage in Watts. The display unit is programmed with the price you pay per kWh (typically 9p) so it can calculate what your cost is for today, this week or this month (if you continue the current level of usage)

Lots of people are getting into exporting the data to draw graphs and publish their usage stats online, and all manner of other interesting things. I haven't got this deep into it yet, but I have learnt a great deal by becoming more aware of my own electricity usage. I thought I would share some of this knowledge in the form of some electricity saving tips.

1. Watts means pounds

One of the first benefits of using the meter is suddenly watts have a real tangible meaning. I knew that lightbulbs were 60-100w, a microwave is 750 or 850watts, etc, but that didn't really have a meaning. When your current electricity usage suddenly leaps up by a 500w and the meter says your cost per day will go up by £1 if you sustain that usage, it becomes a lot more meaningful - and all the more compelling to do something about it. By watching the increase or decrease in current usage when you turn things on or off, you can get a good idea how much power things actually use, and therefore, how much they cost to run. This allows you to make more informed decisions about what you use. Here are some figures based on my observations.

What is it?How much power
does it use?
How much
does that cost?
Lightbulb (energy-saving)
14w0.001p/hour ; 3p/day ;
92p/month; £11.04/year
Lightbulb (standard)
100w1p/hour ; 22p/day ;
£6.57/month ; £78.84/year
Computer/Server/Laptop200w2p/hour ; 43p/day ;
£13.14/month; £157.68/year
Toaster700w6p/hour ; £1.51/day ;
£45.99/month ; £551.88/year
Washing machine
800w7p/hour ; £1.73/day ;
£52.56/month ; £630.72/year
Microwave1,100w10p/hour ; £2.38/day ;
£72.27/month ; £867.24/year
Kettle1,800w16p/hour ; £3.89/day ;
£118.26/month ; £1,419.12/year
Grill2,000w18p/hour ; £4.32/day ;
£131.40/month ; £1,576.80/year
2,200w20p/hour ; £4.75/day ;
£144.54/month ; £1,734.48/year

These figures are based on constant usage which is obviously unrealistic for a lot of appliances - but it makes it easier to compare their relative cost.

You can calculate the cost of a running a given appliance over a given period using the following formula:

Cost (in £) =
power usage (in kilowatts)
× time appliance is running (in hours)
× cost per kilowatt hour (in £)

For example, based on a rate of 9p per kWh, a a 200w computer that is always on, over 1 month (730 hours average) will cost 200/1000 x 730 x 0.09 = £13.14 . Over 1 year it will cost 12 times that i.e. £157.68 . Are you really sure you want to keep that server or computer on all the time?

If you prefer not to do the maths yourself, you can use an online electricity calculator such as this one.

If you want to estimate how much something will cost which is not on all the time, all you need to do is estimate your weekly, monthly or annual hours of usage, and use that figure for the "time" value.

2. Lightbulbs use more electricity than you think

I've always been a little bit slack about leaving lights on when I leave a room - sometimes I remember but not always. Now I can see the impact of doing that more directly, I am much more careful. And I've found that energy saving lightbulbs really can make you significant savings.

For example, let's say you are around the house and using lights for about 5 hours on a weekday and 8 hours on a weekend day (averaging over the year since it's darker in winter & lighter in summer). This works out at about 41 hours of using lights a week. Let's say you have lights switched on in three different rooms on average across that time (the one you're in, and two you forgot to turn off). Let's allow an average 80w per lightbulb. So we have a total weekly wattage of 3 × 80 = 240 watts, for 41 hours = 9.84 kilowatt hours. This would cost 89p a week, £42.51 a year (allowing 4 weeks away from home per year)

Now consider you become a bit more careful and never have more than one light on at a time. Your costs go down to 30p a week, or £14.17 a year.

Now let's consider you go even further, and change all your lightbulbs to energy saving lightbulbs (which typically use 11-14w instead of 60-100w). I've just done this recently and changed all 8 lightbulbs to be energy saving lightbulbs. You'll see why in a moment.

Allowing the same 41 hours a week of lighting, and still being careful having only one on at a time, you get down to 0.574 kWh a week, which would cost only 5p a week, £2.48 a year!!

Even if you were still slack and left 3 light bulbs on at a time on average, you're still only looking at 15p a week, or £7.44 a year.

To put it another way, each energy saving lightbulb you buy could save you up to £10 a year. Which, given they can be found for well under £5, should make them a very worthwhile investment!

3. How many appliances do you have on standby?

I also discovered that appliances plugged into the wall, can use anything between about 5 watts and 30 watts while in standby or even when switched on at the socket but the appliance itself is switched off. I recommend doing a mental audit of every appliance in your house and ask yourself, "Could it live switched off?"

What is it?Could it live in a "switched off at the wall" state?
Kitchen radio, Food mixer, Bread maker, Microwave, Kettle, Oven, Toaster, Bedside Light (x2), File server, Monitor, Computer Speakers, Desktop computer, External Hard Disk, Digital Photo Frame, Printer/Scanner, TV(x2), DVD(x2), VCR, Laptop(x2), Shredder, Wii, XBox, Amp, Tape Deck, DAB Radio, Analog Radio, CD player (x2), Second phone extension, Lamps (x2)Yes
Telephone, PVR (V+/Sky+ etc), Modem, Router, Bedroom Alarm Clock Radio, Wi-fi Ethernet Bridge

As you can see, by far the majority of the appliances (in my house anyway) really don't need to be left switched on. We were able to get our "ambient" household power usage down by around 150 watts by ensuring the bulk of our 30 odd appliances are by default, switched off at the wall.

One of the ways this can be done more easily, particularly at computer desks or TV/hi-fi units with a great many appliances in one place, is to put all the "always on" appliances on a different 4-bar/8-bar than the ones which can live switched off. For example, I have 12 appliances on my TV/hifi unit, but have now moved 8 appliances which can live "off" to a separate 8 bar, which can be kept switched off at the wall by flicking one switch, except when I need one of those appliances. You could also break them down by how frequently you use them - for example I have added the TV & DVD to the "always on" block, for convenience - that way the 8 bar rarely needs turning on.

And it goes without saying that making sure you don't leave your TV, PC etc on standby, will reduce your usage too.

4. Laptops & Computers can have a big impact on your bill

When we realised that our 4 computers (2 laptops, 1 Mac desktop, and 1 linux file server) collectively use around 650 watts of power when they are all on - and that the server and the desktop were "always on" - we made some major changes to our computer usage, which should save us a good £20 or so per month. First, we decided that our server will only be turned on when we need it on (typically 2 or 3 times a week). That saves £7-8 a month right away. Likewise, the Mac is now shutdown whenever it is not in use.
And one final tip, we now run our laptops on battery power until they really need to be plugged into the mains (the thinking being much of the time if it is a short session you will have time to run it on battery). This last one probably only really works because the laptops recharge when in use at work.. I guess it's kind of cheating a bit, but it can help!

In conclusion

I hope that you have found some of this useful, or at the very least, thought-provoking. It really struck me how this is one example where the old adage "Information is power" really does hold true. Once you know in real terms how much you are spending on electricity, you can make informed choices and change your behaviour to save money. Without that knowledge, you may well be burning pounds that you don't need to, which doesn't do the planet or your wallet any good. With forthcoming raises in electricity charges, I am hoping that I am now reasonably well prepared. So - go out and get a CurrentCost meter - you won't regret it. Or even if you don't get a meter, use the information above and out there on the web to work out how you can reduce your bills. By the way, you can also borrow CurrentCost meters from some libraries.. I saw this sign in my local library earlier today.

Disclaimer: All the figures and calculations are my own. If I have made any errors or bad assumptions please do let me know, and I will update this post!