FediMan

All electrical energy eventually gets converted to heat. To economise effectively, you need to find appliances that make lots of heat and either turn them down or use them less. Everything else flows from this.

This is why old-fashioned halogen and tungsten lamps were more expensive to use than modern LED bulbs: they made more waste heat and they therefore ran hotter. You paid for that heat, even if you didn't want it.

Watts, kilowatts, watt-hours — what?

The rate at which an appliance uses electricity is measured in watts (abbreviated as 'W'). You might, for example, have a 7W LED bulb. From 1000W onwards, we use kilowatts (kW), where 1kW = 1000W.

The total amount of energy used is measured in watt-hours (abbreviated as 'Wh'). Turn on your 7W bulb for two hours and you'll use 14Wh. For larger amounts, we use kilowatt-hours (kWh), where 1kWh = 1000Wh.

Kilowatt-hours are the unit of energy that your electricity company bills you for. In the UK, as of October 2022, 1kWh of electricity costs about £0.34. If you use 10kWh of electricity on a given day, you'll pay £3.40 for it. (There'll also be a standing charge, which is often about 40p a day.)

Some examples

With that out of the way, we can talk about typical household appliances.

Let's start with kettles. A kettle runs at high power (typically 2kW or 3kW), but it doesn't run for long, especially if you only boil one mug of water. Suppose it runs at 2kW but switches off after 3 minutes, which is 0.05 hours. The amount of energy it uses is 2kW * 0.05 hours = 0.1kWh, which will cost about 3p. So you can enjoy a cup of tea without guilt, as long as you don't boil more water than you need.

An electric iron runs at a slightly lower power than a kettle — typically 1kW to 2kW — but it runs for longer, and so it costs you more. A 1.2kW iron used for 1½ hours uses 1.2kW x 1.5h = 1.8kWh, and (at October 2022 prices) that'll cost you about 60p. Actually, it's less bad than that, because irons are thermostatically controlled — the heating element comes on when iron is too cool and throws off when it's warm enough. Running it as cool as possible (without reducing its effectiveness) will save money.

A computer uses more energy when it's working harder. Turn it off or suspend it when you're not using it, close programs you're not using, and use uBlock Origin and/or Pi-Hole to avoid wasting processor power on adverts and trackers. (You'll also save Internet bandwidth and improve privacy.)

Laptops use less power than desktops, because laptops have to be able to run on batteries. You pay in other ways — initial price, longevity, performance, keyboard, mouse, screen, repairability, upgradability — but they do at least use less electricity.

Washing machines use more power than you think: they heat water, but they pour it down the drain, so you aren't aware of the heat. Mine draws more than 2kW while it's heating water, much like a kettle. To save money, wash at the lowest temperature that gets your clothes clean, don't run a half-empty machine, and try to wash on warm days, when the water coming into your house is warmer and needs less heating.

(For some off-topic savings, experiment with using less detergent, see if supermarket own brands are as effective as the big names, use limescale remover to keep the heating element efficient, and don't use fabric conditioner. Some people find it helpful to replace fabric conditioner with vinegar, but I don't even use that.)

Tumble dryers and ovens warm up the whole room. They obviously draw a lot of power. Use them as little as possible. (I tumble-dry towels for 20 minutes before hanging them, because Mrs Wife insists on it. Everything else gets air-dried.)

TVs and Hi-Fi use a medium amount of energy. The bigger the screen, the more power-hungry a TV is. Turn these things off when you're not using them. If you have the option of watching the programme you want via an app on the TV rather than powering up a set-top box, that may save a few watts. (Or possibly not, if it means powering up more circuitry inside the TV.)

Older TVs drew a lot of power if you turned them off using the remote control, but modern ones don't. Advice to turn the TV off at the wall is outdated unless your TV is ancient.

When in doubt, measure.

Fridges and freezers run at a reasonably low power, but they're always on, and so they use a fair amount of energy each day. To save money, move them away from heat sources (such as cookers), keep them defrosted, and keep the radiator at the back of the unit clean and unobstructed. This way, the compressor will be able to shift heat efficiently, and won't need to run for so many hours every day. Anyone who stands with the freezer door open while holding a long conversation deserves to be shouted at.

Your boiler and central heating system both use electrical power, even if their main source of power is gas or oil. (Your central heating system pushes water round the house using an electric pump, which typically draws several hundred watts.) Insulate the house where it's practical, don't heat rooms you're not using, and turn off the heating altogether whenever you can. It is not more efficient to leave the heating on when you leave the house: a warm house loses more heat per minute than a cool house, so let it cool down while you're out and then warm it up again when you come in.

A surprising number of appliances draw energy even when they're apparently turned off. I understand why our hi-fi does it — it's waiting for me to wake it up it using Spotify — but why does the washing machine use 3W, all day, every day? I have no idea. 3W doesn't sound like much, but it works out at 1kWh every fortnight, or 25kWh a year. That's real money. Consider borrowing a power-measurement plug and turning things off at the wall if they waste electricity like this.

We've already talked about lighting. Use LEDs or (at a pinch) compact fluorescents, not tungsten or halogen bulbs. People think halogen bulbs don't take much power because they run at low voltage, but that's a myth. Voltage and power are not the same thing.

If you have an electric or induction cooker, try to boil water in the kettle rather than on the cooker: it's more efficient. When using the hob, put lids on your saucepans and turn them down a bit. Where possible, use a pressure cooker. People think you have to boil pasta with lashings of water at a rolling boil and with no lid, but you don't. (Mind, I wouldn't cook it in a pressure cooker, either. :–)) You can just bring it to the boil, cut the power, perhaps cover the pan with an old cloth, and wait for it to cook.

You can tell that charging a phone doesn't take much electricity, because the phone and the charger are small and they don't get very hot. (When you're looking at battery chargers, you need to include the heat that the device makes when you're using it, not just when you're charging it, but phones don't make much heat when you use them, either. If they did, they'd burn your hand.) Do unplug idle chargers for safety reasons and to prolong the life of the phone the battery, but don't expect to save much money.

Similarly, an ADSL router doesn't make much heat, and so you know it's cheap to run. You should leave it powered on all the time: if you keep turning it off, your ISP will think that the line is bad, and will fall back to a lower speed. (Don't panic if you've been doing this: just leave the router turned on, and it'll fall forward again within a few days.)

A UPS can be surprisingly inefficient. Does it get warm and stay warm, even when all the devices it powers are turned off? Measure it, work out what it's costing you each year, and consider replacing it with a more efficient model next time its battery fails. (A simple worked example: there are just under 9,000 hours in a year. So a UPS that draws 10W on idle, even when the battery is charged, wastes 90kWh per year. That costs about £30 per year at October 2022 prices. I have one cheap UPS that does even worse than this. It's on its second battery now, but that'll be its last.) Oh — when buying a UPS, as well as looking at idle power, check that the battery can be replaced: they don't last as long as you'd hope. If you already have a failed UPS battery and the manufacturer says it can't be replaced, check YouTube: it can often be done.

Other thoughts

People say great things about smart meters with in-house displays (IHDs), but I don't think they're that useful. So many things come on and off automatically — fridge, freezer, central heating, security lights — that using an IHD for accurate measurements is impossible, even if you're the only person in the house. I would resort to an IHD to measure a hard-wired high-power appliance such as an oven or hob, where there was no 13-amp socket and I couldn't use a power-measurement plug.

Generally, when buying new stuff, look at energy efficiency ratings and be prepared to pay a bit more for frugal appliances if you think it'll save money in the long run.

The UK's National Grid has promised a rebate scheme, starting on 1st November 2022, for households that shift energy use away from peak hours. You probably need a smart meter to benefit. If you can, make the most of it.