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Energy Mythbusting Is it cheaper to have heating on all day?

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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 know if common tricks to cut energy usage really work.

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

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Myth busting

Should you keep your heating on all day on low, and what about painting radiators black? These were two of the most common questions MoneySavingExpert.com users on Facebook and Twitter wanted answering after we asked what energy-saving tricks you employ, and any other queries you had. But are these myths, or fact?

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.

Q. Should I leave the heating on low all day, or turn the thermostat up and down?

a. This one divides opinion. The EST and British Gas say you'll save energy, and therefore money, by only having the heating on when it's required. Using a timer is best, because your thermostat is designed to turn your heating system on and off to keep your home at the temperature you set it.

However, another school of thought says it is best to keep it on at a low temperature all day and turn all radiator valves to the max, and the boiler down to the minimum. So it's a grey area.

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.

Q. Should I leave the hot water boiler on all the time, or on and off as needed?

a. 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 with your energy company.

Q. Is it cheaper to use radiators or electric heaters?

a. 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 timer.

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

a. 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.

MSE adds: We asked British Gas the same question. While it agrees that leaving chargers in a socket uses energy (if the charger is warm, it's using energy), it says 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.

Q. Should I run appliances at night?

a. 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 with your energy company. For more help, see Economy 7: Is It Right For You?

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

a. It's best to have as many controls as possible, so you can fully control 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 how thermostatic radiator valves work.

Q. Should I turn individual radiators down at the valve or will it only make a difference if controlled via the main thermostat?

a. There's little difference. By turning your radiators down or off using thermostatic radiator valves on the side of them, or by reducing your room temperature via a thermostat, you decrease the amount of heat your heating system has to generate.

Your room thermostat only switches your heating off when the set temperature has been achieved, so turning your thermostatic radiator valves down will mean your radiators will not get as hot and will gently heat your home to the set temperature.

If you have them on high, your radiators will emit lot of heat until the set temperature is met.

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

a. 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.

MSE forum feedback: This answer was disputed by some. While British Gas says black is a more efficient colour at absorbing and then giving off heat, it says that by painting a radiator, the paint itself can act as an insulator. This means less heat is transferred to the room. It 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.

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

a. 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.

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

a. 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.

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

a. Turn them off when you don't need them. Also avoid leaving TVs and other devices on standby.

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

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

a. 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 adds: After suggestions from our forum, we checked out whether drying clothes indoors can cause damp, which creates its own problems. 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."

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

a. This depends what you're after. Halogen heaters are directional. Once on, and directed towards you, 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, depending on your home's insulation.

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

a. 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.

Q. Is a combi boiler cheaper to run?

a. 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.

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