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energy mythbusting

Energy Mythbusting

Spend less on gas and electricity

Andrew Capstick
Andrew Capstick | Edited by Steve Nowottny
Updated 29 December 2020

Should you keep your heating on all day on low? And what about painting radiators black? We've gone on an energy mythbusting mission to see whether the energy efficiency experts think common tricks to cut energy usage really work. With so many of us at home more often right now, and with the weather getting colder, this is key. But it's not just about using less, you could save £100s/year by switching – do a five-minute comparison via our Cheap Energy Club. 

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Energy-saving tips 'n' tricks (and how we've answered 'em)

We've answered the questions we can below, but as we are experts on MoneySaving, not the intricate science behind using less energy, on the more techy questions we've sought advice from the specialists at the Energy Saving Trust, and consulted other experts – including British Gas and an independent plumber – while also finding out what MoneySavers on Facebook, Twitter and the MSE Forum have 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 these tips will at least help you make an informed decision.

Here are the key questions you asked, with their answers below.

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

    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 (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.

    leaving heating on low

    However, it's not quite that clear-cut. Some specialists disagree – and 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, and say 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, 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 the house will be warm when needed, but you're not pumping out energy all day.

    illustration

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  • Should I put clingfilm on the windows?

    Bizarrely, the Energy Saving Trust says this one actually works – although clingfilm is normally used to wrap up your sandwiches, it can actually help keep your home warm. The idea is that putting a sheet on your window traps a small layer of air which can help stop heat escaping.

    The Trust says you can use any material for the second layer of glazing, as long as it's transparent and airtight. However, while clingfilm works in theory, in practice you'll probably want to use 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 than when dealing with a single-glazed window.

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

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

    water tap

    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 required.

    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. 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 nine tips to max it, eg, beware when the clocks move – Economy 7 timers can be set incorrectly.

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

  • Do phone or laptop chargers still use electricity when plugged in but not connected to a device?

    Try to unplug chargers when not in use. British Gas says on its website that a lot of chargers use energy when left in a socket (if the charger is warm, it's using energy).
    laptop charging

    A lot of devices, such as games consoles, laptops and TVs, also 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.

    The Energy Saving Trust estimates that a typical household wastes around £35 a year by leaving devices plugged in or on standby.

    Want to know how to save £100s/yr on your bills too? Check now if you can switch and save with our Cheap Energy Club.

    illustration

  • 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), measure your usage and automatically send meter readings to your supplier each month. However, they can help you identify ways to save energy via the in-home display that comes with your smart meter.

    This is a small gadget that 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, the idea is that it will help you spot ways to cut back. For more, see our Smart Meters guide. 

  • Is it cheaper to use radiators or electric heaters?

    The Energy Saving Trust says electric heaters are one of the most expensive forms of heating. It says the cheapest way to heat your home is by using an efficient gas central heating system, with a full set of thermostatic radiator valves, a room thermostat and a timer.

  • Should I run appliances at night?

    washing machine

    If you're on an Economy 7 or 10 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.

    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. Installing thermostatic radiator valves and using them with your thermostat could save £75 per year according to the Energy Saving Trust.

    It recommends using the thermostat to control the heat in your main living space and using thermostatic radiator valves to lower the heating in rooms you don't use as often.

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

    thermostat vs radiator valve

    Thermostats control your boiler, while radiator valves control the water flow through each individual radiator.

    Your thermostat controls your home's temperature, so once it hits the temperature you set on the thermostat, the boiler will go off until the room temperature drops again.

    Radiator valves are an extra control which you can use to set the temperature of each individual room (other than where your main thermostat is). This means you can set some rooms to be cooler than others if you don't use them very often (saving energy and money).

    When the temperature in that room rises above what's set on the radiator valve, it will stop water flowing through that particular radiator – the boiler will still be on to heat other rooms, but it will use less energy.

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

    illustration

  • Would painting my radiators black or putting reflective panels behind them 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. Radiator panels can save energy, but not very much. 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.

    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.

    illustration

    As for putting reflective panels behind radiators, yes, the Energy Saving Trust agrees that 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 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?

    We couldn't find one single 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?

    open door

    It's better to keep doors closed for rooms that you don't heat, 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 entering.

  • 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 to be 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.

    illustration

  • 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. Drying your clothes indoors on an airer can cause problems with condensation and damp, especially in old and poorly-insulated homes, so it is best to dry your clothes outdoors whenever the weather allows.

    clothes on washing line

    According to the National House Building Council, 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?

    halogen heater

    This depends on 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.

    Usually, it's best to use your central heating to heat your home rather than relying on electric heaters, especially if you have gas central heating, according to the Energy Saving Trust. If you're only using a couple of rooms, you can use thermostatic radiator valves so that your central heating isn't heating empty rooms. Electricity is much more expensive than gas, so using electric heaters can ramp up your energy bills.

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

    Generally, using oil for hot water is cheaper, owing 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 Energy Saving Trust says whether a combi or a standard boiler is cheaper to run will depend on your lifestyle and how much hot water you use.

    With a standard boiler, water is heated by your boiler and stored in a hot water tank for when you need it. With a combi boiler, you don't have a hot water tank and instead water is heated up instantly when you turn on the hot tap.

    If your household doesn't use too much water, combi boilers can be more efficient, as they don't leave water sitting in a tank where it can lose heat. However, combi boilers tend to be less efficient at heating water in the first place, so if you're a large household using lots of water it might be cheaper to have a standard boiler with a well-insulated tank.

    The main thing which will affect how expensive your boiler is to run is its efficiency. Having an A-rated condensing boiler (standard or combi) will be cheaper to run than an older non-condensing boiler.

  • 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 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 rule of thumb is to keep your heating at a minimum 12 degrees, rather than switching it off.

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