Energy mythbusting

12 energy-saving conundrums explored

With energy bills still close to double what they were before the energy crisis, using less energy is a key way to cut bills, and there are obvious ways to do this, such as turning your lights and heating off when you go on holiday. But this guide aims to crack the less-obvious energy conundrums, such as whether it's better to leave your heating on all day and if it's worth turning devices off standby mode.

Key energy-saving guides

Energy mythbusters

In this guide, we debunk 12 energy-saving conundrums.


The big savers to cut your energy bills.

Tips to keep yourself warm for less.

Energy saving myths (and how we've debunked 'em)

There are a lot of urban myths and "quick tricks" for saving money on your energy bills. Many are a bit rubbish but some do offer simple and cheap ways to reduce your energy consumption (and your monthly bill).

We've rounded up 12 of the most common questions we get below. As we are experts on MoneySaving – and not the intricate science behind using less energy – we've sought advice from the specialists at the Energy Saving Trust, and other experts for the more techy questions, including British Gas and an independent plumber, whilst also finding out what MoneySavers on Facebook, Twitter and the MSE Forum had to say.

As is often the case in the world of science, not everyone agrees on every point so there isn't always a definitive answer, but our research should hopefully help you make an informed decision.

1. Is it cheaper to leave the heating on low all day or only turn it on when I need it?

This is a hotly debated one. According to experts at the Energy Saving Trust, the idea it's cheaper to leave the heating on low all day is a myth. They're clear that having the heating on only when you need it is, in the long run, the best way to save energy, and therefore money. (A timer's best, as your thermostat turns your heating on and off to keep your home at the temperature you set.)

It's all about the total amount of energy required to heat your home. A certain amount of energy is constantly leaking out of the building (how much will depend on how good your insulation is). The Energy Saving Trust says if you're keeping the heating on all day, you're losing energy all day, so it's better to heat your home only when you need it.

But it's not quite that clear-cut...

Some argue you should keep the heating on constantly for an entirely different reason.

They advocate keeping the heating on low all day, turning all radiator valves up to the max and the boiler down to the minimum. This is because condensation collects within the walls each time the heating is turned off. Some argue that this condensation can help to conduct heat outside the home – meaning you lose heat more quickly and use more energy as a result.

MSE Forum feedback: Some complain that only having the heating on when required risks you being cold, as it takes time to heat up homes. That may be true, but this is a MoneySaving site, so we're focused on cost.

As a balance, you could switch the timer on a little earlier, so your home will be warm when needed, but you're not pumping out energy all day.

2. Should I put clingfilm on the windows?

Although clingfilm is normally used to wrap up your sandwiches, the Energy Saving Trust says it can actually help keep your home warm too.

Putting a sheet of clingfilm on each of your windows traps a small layer of air, which can help to stop heat from escaping. The trust says you can use any material for this second layer of 'glazing', as long as it's transparent and airtight.

While clingfilm works in theory...

Ideally you'd want to install specialist secondary glazing as it'll last longer. If you have double glazing, adding a third layer could make you a little warmer, but the benefit will be much less noticeable than with a single-glazed window. 

If your windows are draughty, it's worth fixing that as well as adding secondary glazing, or you'll only get half the benefit.

3. Do devices on standby or chargers left in sockets still use electricity?

Yes. British Gas says that chargers and appliances will still use electricity when left in sockets – so it's important to turn them off at the plug when you're not using them. 

A lot of devices, such as games consoles, laptops and TVs, draw small amounts of power when not in use but still plugged in and turned on at the socket. This is sometimes known as 'vampire power'. You can easily avoid using this standby power by switching devices off at the wall.

The Energy Saving Trust says you can save about £60 a year by turning off your appliances at the plug when you're not using them.

However, it's EU law that TVs and other devices made since 2013 can't use more than 0.5 watts in standby mode. To show the scale of it, a TV left on standby for 20 hours a day would cost about £1 a year. So while you may not save as much as the Energy Saving Trust says, it can still be worth doing – all devices will still use a small amount of power, and this can add up.

4. Will smart meters save me money?

No – at least not on their own.

Smart meters simply replace your existing gas and electricity meters (one for each), keep track of your usage and automatically send meter readings to your supplier each month.

However, they can help you to identify ways to save energy via their in-home display. This small gadget communicates wirelessly with your smart meters, monitoring what energy you're using and showing you how much it costs, in near real time.

With more information on your day-to-day energy use, you'll be able to spot ways to cut back. For more, see our Smart meters guide.

5. Should I run appliances at night?

This will depend on who supplies your energy and your tariff. If you're on an Economy 7 or 10 tariff, (also with some specialist EV tariffs), you'll pay less for energy you use during the night, but a higher rate than average during the day. If you're on another tariff, you'll pay the same amount regardless of what time of day it is. 

If you're unsure what tariff you're on, check your latest energy bill or ask your energy company.

Important. Before you use an appliance at night, check it's safe. For example, the fire service says you should never run the tumble dryer while you're asleep, as it's a common cause of fires in the home.

6. Would painting my radiators black help?

Where painting your radiators black is concerned, the answer's no, according to the Energy Saving Trust. It's best to keep them the standard white, although the difference is not huge. 

MSE Forum feedback: This answer was disputed. Some say black is a more efficient colour at absorbing and then giving off heat, while others say that by painting a radiator, the paint itself can act as an insulator. This means less heat is transferred to the room.


What about radiator panels?

Radiator panels can save energy, but not very much. It's more important that your walls are insulated, to prevent the heat leaking out of your home altogether. See The Great British Insulation scheme guide for more information. 

As for putting reflective panels behind radiators, yes, the Energy Saving Trust agrees that these could help cut energy use. They reflect heat from the radiator back into the room, so it doesn't escape through external walls. The trust says homes with uninsulated walls will get most benefit.

7. Should I leave lights and appliances on, or turn them on and off each time?

The Energy Saving Trust recommends turning off lights when leaving a room, regardless of how long for (and being mindful of how many lights you have on at any one time). Also, avoid leaving TVs and other devices on standby.

MSE Forum feedback: While turning devices off completely saves energy, the difference can be negligible. So don't bank on this solving all your energy woes.

8. Should you leave your heating on if you're going away?

Yes – in the winter. To prevent frozen pipes, which can cause £100s of damage, the Energy Saving Trust recommends you leave the heating on to some degree during winter, even if you're not there.

Check your home insurance policy before you go away. The general rule is to keep your heating at a minimum 12 degrees (but some say at least 15 degrees), rather than switching it off completely.

9. If my heating is on, should I keep my internal doors open or closed?

It's better to keep the doors of rooms that you don't want to heat closed, says the Energy Saving Trust.

Radiators, electric panel heaters and convection heaters all work by creating a convection current in a room. As hot air rises, it circles around to the other side of the room, cools and sinks, and travels back along the floor to the heater to be reheated again.

Closing doors makes sure this current remains within the designated space, and stops cold air from getting in.

10. Is it cheaper to boil water in a microwave?

With kettles being power-hungry appliances – using up to 3,000 watts – you may look to alternatives to boil water for your cuppa. We did a quick number crunch to find out which is cheaper: boiling water in a kettle or a microwave.

Method Power rating (watts) Time to boil Cost of electricity (1)
Microwave 1,120 watts (gives output of 800 watts) 2 minutes 30 seconds 1.4p
Kettle (2) 3,000 watts 1 minute 1.5p

(1) Cost based on July's Energy Price Cap rate of 30.11p a kilowatt hour. (2) Kettle filled with one mug of water.

In our small experiment, boiling a mug of water in a microwave was slightly cheaper than boiling it in a kettle, though there's not much in it.

Although it's technically cheaper to use a microwave...

Electrical Safety First warns that boiling water in a microwave can be dangerous as you could overheat the water past boiling point and cause it to explode. On the other hand, a kettle is designed to switch off once it reaches boiling point.

When using a kettle, it's also more economical if you only boil what you need. The Energy Saving Trust reckons you could save £12 a year this way compared with overfilling it each time. See our Energy saving tips guide for more.

11. Is it expensive to run an electric fan?

Many have asked us if using an electric fan to keep cool in summer will burn a hole in their pocket. With the energy market in crisis, people have been worrying more often about energy prices.

But the good news is you CAN use an electric fan to manage the heat without breaking into a cold sweat at the cost.

A typical 12-inch 35-watt desk fan would cost around 1p an hour to run based on the current (July) Price Cap rates, so about 8p if you leave it on all night. A big 50-watt tower fan wouldn't cost much more – about 1.5p an hour. If you have a large floor fan, they typically range between 10 watts and 120 watts, costing up to 4p an hour. 

12. Should I keep the hot water boiler on all the time, or turn it on and off as needed?

If you have a gas, oil or LPG (liquefied petroleum gas) central heating system, the experts say it will always be cheaper to set the system timer so the hot water comes on only when you need it.

However, if you use an electrical immersion heater and have an Economy 7 or 10 tariff (where energy is cheaper at night), it's cheaper to heat your water during the night. You'll need to make sure your tank is well insulated to prevent it cooling during the day though.

If you're unsure what tariff you're on, check your latest energy bill or ask your energy firm.

If you've got any other burning energy questions you'd like answered, please suggest them in the Energy mythbusting forum thread.

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