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Energy Mythbusting

Spend less on gas and electricity

Should you keep your heating on all day on low? And what about painting radiators black? We've gone on an energy mythbusting mission, so you can find out if common tricks to cut energy usage really work.

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Switching your energy tariff could cut your bills by £100s. It's the same electricity, same gas and same safety - only service, billing and price changes. Some can save just by changing tariff with their existing supplier.

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We got users on Facebook and Twitter to tell us their energy-saving tips 'n' tricks - then we asked the Energy Saving Trust (EST) and British Gas to tell us if these actually work.

Here are the key questions you asked, with their answers below. We have also included feedback from our forum where users have added extra tips.

Should I leave the heating on low all day even when I'm out, or turn it up only when I need it?

According to leading energy experts at the Energy Saving Trust, as well as British Gas, the idea that it's cheaper to leave the heating on low all day is a myth. They're clear that you'll save energy, and therefore money, by only having the heating on when it's required. (Using a timer's best, because your thermostat is designed to turn your heating on and off to keep your home at the temperature you set it.)

The key thing to understand here is that it's all about the total amount of energy required to heat your home.

It's a given that a certain amount of energy is constantly leaking out of your home (though exactly how much will depend on how good your insulation is). So if you're keeping the heating on all day you're losing energy all day - it's better to heat your home only when you need it, even if that means whacking the temperature up high.

However it is worth being aware that while the most commonly cited argument for leaving the heating on (that it's cheaper than heating the home up from cold) is a myth, there are a few specialists who argue you should keep the heating on constantly for a 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, and say that the problem with turning the heating on and off is that every time it's turned off, condensation collects within the walls. This condensation can help conduct heat outside the home, they say - meaning you leak heat more quickly and so will use more energy as a result.

MSE forum feedback: Some complain only having the heating on when required risks you being cold, because it can take time to heat up homes, especially larger ones. Of course, that may be true, but this is a MoneySaving site, so we’re focused on cost.

Yet as a balance, if you go down the route of having the heating on only at certain times, you could switch the timer on a little bit earlier, so the house will be nice and toasty when needed, but you’re not pumping out energy all day.

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, it will always be cheaper to time the system so the hot water comes on only when required.

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

For more on this, our Economy 7: Is It Right For You? guide sets out to crack whether those with it should stick, and if those without it should switch. It also includes 10 tips to max it, eg, beware when the clocks move - Economy 7 timers can be wrongly set.

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

Is it cheaper to use radiators or electric heaters?

Electric heaters are one of the most expensive forms of heating. Generally, the cheapest way is using an efficient gas central heating system, with a full set of thermostatic radiator valves, a room thermostat and a timer.

Do phone or laptop chargers still use electricity when they're plugged in, but not connected to the device?

Try to unplug chargers when not in use. A lot of devices draw power when plugged in and not in use. This is sometimes known as 'vampire power'. Using this standby power can be easily avoided by switching devices off at the wall.

British Gas says on its website that leaving chargers in a socket uses energy (if the charger is warm, it's using energy). It says that some chargers (including those from Apple) turn themselves off when not connected to a device. It adds that, generally, branded chargers are more efficient than non-branded ones.

Should I run appliances at night?

If you're on an Economy 7 tariff, you'll pay less during the night, but a higher rate than average during the day. But if you're on another tariff, it doesn't make any difference.

MSE tip: This has been answered from an energy use perspective. Before you use an appliance at night, check it's safe. If you're unsure what tariff you're on, check your latest energy bill or ask your energy company. For more help, see Economy 7: Is It Right For You?

Should I set thermostats on individual radiators, rather than using the main thermostat to control all of them?

It's best to have as many controls as possible, so you're in charge of the way you want your home to be heated. A room thermostat saves, on average, about £70 a year, whereas having all your radiators installed with thermostatic radiator valves can save around £10 a year. See this guide from Drayton Controls for more on how thermostatic radiator valves work.

What’s the difference between controlling the heating using the thermostat or radiator valves?

There's little difference in terms of energy efficiency, but what can change is how quickly the room is heated up.

The thermostat controls the room temperature, so once it hits the temperature you set on the thermostat, the radiators will go off, until the room temperature drops again.

Turning your radiators up and down using thermostatic radiator valves on the side of them affects how quickly the room heats up. If you have them on high, your radiators will emit lots of heat quickly until the set temperature is met and vice versa.

Please suggest any changes or questions you'd like answered in the Energy mythbusting thread.

Would painting my radiators black or putting reflective panels behind them help?

Where painting your radiators black is concerned, the answer's no. It's best to keep them the standard white, although the difference is not huge. It's more important to insulate your walls to prevent the heat leaking out of your home altogether, see our Free insulation guide for more details.

MSE forum feedback: This answer was disputed by some. Some suppliers say black is a more efficient colour at absorbing and then giving off heat, while the British Gas website says that by painting a radiator, the paint itself can act as an insulator. This means less heat is transferred to the room. British Gas's website adds: "Radiators are often painted with white gloss paint, but would be better at radiating heat if they were painted with black matt paint."

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

Should I have the gas fire on in the living room, or all the radiators in the house?

There is no one answer for this. It's highly dependent on the heating system you use, and the usage in other areas of the house.

If my heating is on, should I keep doors open or closed for each room?

It's better to keep doors closed for the area you want heated.

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.

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

Turn them off when you don't need them. 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.

Should I use a tumble dryer, or place washing on an airer with heating on?

An airer is better because tumble dryers use a lot of energy.

Try timing it so you put your washing out on a clothes horse during the hours your heating comes on. Normally, that way you wouldn't use any more energy.

MSE tip: After checking this out, we found that the National House-Building Council says on its website: "If you need to dry clothes indoors, open the window and close the door of the room where the clothes are drying, so moisture can escape rather than circulate around your home."

Are halogen heaters cheaper than other portable heaters and central heating?

This depends what you're after. Halogen heaters are directional. Once on, you instantly feel the heat. As soon as you turn them off, the heat quickly dissipates. Convection heaters, electric panel heaters or free-standing electric radiators work by heating the air around them to create a convection current. They take some time to heat a room, but once turned off the heat lingers.

Should I use an immersion heater to heat water, or oil-fired central heating?

Generally, using oil for hot water is cheaper, due to the higher average cost of electricity. However, if you're able to use a lower rate electricity tariff (such as Economy 7, where power is cheaper at night) at the right time, it can work out more cost-effective. This is also dependent on the efficiency of your central heating system.

Is a combi boiler cheaper to run?

The cost is largely dependent on its efficiency. An A-rated combi condensing boiler will cost less to heat the same amount of water as an older, less efficient non-condensing boiler. But combi boilers can be less efficient at heating hot water than other boilers. See this Which? guide for what a combi boiler is.

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

To prevent frozen pipes, which can cause hundreds of pounds of damage, the Energy Saving Trust (EST) recommends you leave some heating on even if you're not there.

If you can set your thermostat so the heating comes on when it drops below 5 degrees that should do it. It adds that if your thermostat doesn't go down that far, setting it to come on for a couple of hours a night at about 15/16 degrees should also be enough as it can take a long time for pipes to freeze.