Energy Detective
Check your answers
Here's every device sorted from the least energy-hungry to the most. Within each colour band, items are ordered from lowest to highest too.
Two things decide how much energy something uses: how powerful it is and how long it runs. A kettle is super powerful but only runs for two minutes. A fridge is not very powerful at all — but it never switches off, so it adds up. Watch out for both kinds of energy user as you read!
The little number in watts (W) tells you how powerful each thing is. 1,000 watts = 1 kilowatt (kW).
🟢 Very low energy use
- Smoke alarm ~0.0001 W Sips a tiny trickle of power from a battery so it's always ready. Uses less in a whole year than a kettle uses making one cup of tea.
- Clock ~1 W Only has to move its hands or light up a few numbers, so it barely needs any power at all.
- Phone charger ~5 W Trickles a small amount of power into your phone. Once the phone is full it uses hardly anything — but it's still tidy to unplug it.
- Toothbrush charger ~2 W Slowly tops up the brush's battery while it sits on its stand. Very gentle on energy.
- Smart speaker ~3 W Sits quietly listening for your voice, which takes only a little power — a bit more when it's playing music.
- Broadband router ~7 W Low power, but here's the trick: it's switched on 24 hours a day, every day, so it quietly adds up over time.
- LED bulb ~8 W Modern LED lights use about a tenth of what old-fashioned bulbs used to. Bright light for very little power.
- Bedside lamp ~8 W With an LED bulb inside, a bedside lamp is one of the gentlest things in your room. (An old-style bulb would use far more.)
- Tablet (charging) ~10 W A bit like a big phone — it only needs a small amount of power to charge up.
- Laptop (idle) ~10 W When it's just sitting there not doing much, a laptop is very efficient. It uses more when it's working hard (see the next band!).
- Small LED TV ~15 W A small modern telly uses surprisingly little — about the same as a couple of LED bulbs.
🟡 Low energy use
- Phone (on a call) ~5 W A phone uses very little to make a call — but its screen and games use a bit more, which is why it's crept into this band.
- Handheld games console ~15 W Small screen, small battery, so it's fairly gentle — though playing for hours adds up.
- Ceiling fan ~30 W Spinning a fan blade doesn't take much power — far less than an air conditioner would.
- Electric fan ~40 W A desk or floor fan just moves air around, so it sips power compared to anything that heats or cools.
- Laptop (in use) ~50 W When it's working hard — games, videos, lots of tabs — a laptop uses several times more than when it's idle.
- Printer ~50 W Uses almost nothing while waiting, then a short burst when it actually prints a page.
- Large LCD TV ~80 W A big telly needs more power to light up its bigger screen, especially older ones.
- Desktop computer ~100 W A normal desktop sits here, but a powerful gaming PC can use three or four times as much.
- Fish tank / aquarium ~50 W The pump and light aren't powerful, but they run all day and night — a sneaky long-time energy user.
- Slow cooker ~200 W Low power for a cooker, but it bubbles away for six or more hours, so the energy quietly builds up.
🟠 Medium–high energy use
- Fridge-freezer ~150 W Not very powerful — but it's the king of long-time users, running every minute of every day to keep your food cold.
- Games console (PS5/Xbox) ~200 W Much hungrier than a handheld — all that gaming power needs serious electricity, especially during big games.
- Dehumidifier ~300 W Pulls water out of the air. Medium power, but often left running for hours, so it mounts up.
- Vacuum cleaner ~900 W That strong sucking motor needs lots of power — but you only use it for a short time.
- Coffee machine ~1,000 W Heating water is always power-hungry. The good news is it only runs for a minute or two per cup.
- Microwave ~1,000 W Powerful, but a great example of "high power, short time" — it heats food fast then switches off.
- Iron ~1,200 W Gets hot enough to smooth clothes, which takes plenty of power. Used in short bursts though.
- Air fryer ~1,500 W Heats up fast and cooks quickly, so even though it's powerful, it often uses less than a big oven.
- Hair dryer ~1,800 W Blowing out hot air takes a lot of power — but only for a few minutes at a time.
- Washing machine ~2,000 W Most of its energy goes on heating the water. A cooler wash uses much less.
- Dishwasher ~2,000 W Like the washing machine, heating the water is the hungry part. An eco setting saves a lot.
🔴 High energy use
- Toaster ~1,200 W Glowing-hot wires need lots of power — but toast is quick, so it doesn't run for long.
- Hob ~2,000 W per ring Whether electric or gas, cooking on the hob uses a lot of energy — and several rings at once adds up fast.
- Electric heater / radiator ~2,000 W Turning electricity straight into heat is very power-hungry, and heaters often run for hours.
- Oven ~2,500 W Electric or gas, an oven heats a big space to a high temperature and stays on for a long time — a real energy guzzler.
- Tumble dryer ~2,500 W Drying clothes with hot air for a full cycle uses a huge amount — hanging washing up uses none!
- Kettle ~3,000 W One of the most powerful things in the house! It boils water in a couple of minutes — and because we boil it so often, it really matters.
- Immersion heater ~3,000 W Heats a whole tank of water using electricity. Powerful and slow, so it uses a lot.
- Boiler ~3,000 W electric / lots of gas Heats your hot water and warms the whole home. One of the biggest energy users of all, whether it runs on electricity or gas.
- Hot tub ~6,000 W Keeping a big tub of water hot around the clock makes this one of the very hungriest things you can own.
- Electric car charger ~7,000 W Filling up a car battery takes enormous energy — about as much as the rest of the house put together while it's charging.
- Electric shower ~9,000 W Heats water instantly as it flows, which is why it's one of the most powerful things in the whole house — even though showers are short.