Should you leave the heating on all day rather than turning it on and off? Does turning up your thermostat heat the house up faster? We often hear suggestions to save energy at home that are simply not true. Our specialist energy advisors tackle some common energy-saving myths…

It’s better to leave the hot water heater on all the time, rather than turning it on and off

This is a very common energy saving myth. But in fact, you really don’t need to be heating your water all the time. Your immersion heater or boiler will heat up hot water which is stored in a tank. As long as the tank has a good insulating jacket, it will keep the water hot all day, without needing to be constantly reheated. You can use a timer to heat your water for an hour or two each day just before you would usually need hot water for baths or showers. Modern washing machines, dishwashers and electric showers take cold water and heat it themselves so you don’t need a supply of hot water waiting for them in the tank.

If you’re on Economy 7, make sure your electric immersion tank is coming on for a couple of hours in the night when you are getting electricity at a much cheaper, off-peak rate.

You should leave the heating on all day, rather than turning it on and off

Another common one! And also a myth. Don’t pay for heat that you’re not using! If you are out during the day (or tucked up in bed at night), you don’t need the heating on. Even if you turn your thermostat down a bit, your boiler will keep firing up and using energy (and cost you money) at times when you won’t feel the benefit. Instead, programme your central heating using the timer so that it switches off when you’re out or in bed, and switches back on to warm up the house about half an hour before you get home or before you get up.

Turning the thermostat up will heat the house up faster

Myth. If you come home to a cold house, it’s tempting to whack the thermostat up in the hope that this will make the place warm up faster. Sadly it wont; your boiler works at the same constant speed regardless of whether you set your thermostat to 20C or 30C. In fact, you’re likely to find that later in the evening you’ll be sweltering – and wasting a lot of money – as your boiler doesn’t stop when the room is comfortable. Set the thermostat to a sensible room temperature, between 18-21C, and then leave it alone.

If I turn all the radiators down low, I’ll save money

True. But only if you also turn your thermostat down at the same time. If you turn your radiators down low but still have the thermostat set to 21C, your boiler will keep running until the room temperature reaches 21C – and this will take a long time with the radiators on low. So if you want to save money and are comfortable with your house a little cooler, make sure you turn down the thermostat, not just the radiators.

The point of thermostatic radiator valves (the ones with numbers on that you can turn up and down) is to set different rooms to different temperatures, so that you’re not wasting money heating rooms you aren’t using.

And it’s not a good idea to turn a radiator off permanently in an unused room, as this can lead to damp and mould. Leave them on low instead, and close the doors.

It’s cheapest to stay in one room with an electric heater or a gas fire

Sometimes true. It might seem obvious that if you’re alone in the house and cold, you’re better off sitting next to a heater in one room than turning the central heating on. This can be untrue, depending on what type of heater you use.

Electricity and bottled gas are both far more expensive per unit than mains gas. Electric fan heaters and portable gas fires are two of the biggest energy guzzlers, and if you have them on for a matter of hours then it may be cheaper just to turn on your central heating with the radiators on a low setting in the rooms you’re not using. However, oil filled radiators can be a good option for heating one room, particularly if you have a large property or your boiler is old, or you don’t have thermostatic radiator valves (TRVs).

Here’s some information on how much energy portable heaters use.

Night storage heaters are expensive to run

Potentially true if you don’t know how to use them properly. Lots of people have gripes with night storage heaters, but if you understand how to use the controls and you’re on the Economy 7 electricity tariff, they are the cheapest form of electric heating. If you don’t understand how the controls work then you can quickly run out of heat so it seems as if they aren’t working, or they can charge up with more heat than you need and become expensive to run.

Read our simple guide to night storage heaters before you despair.

It takes more electricity to turn lights off and on again than to leave them on

This is an energy saving myth. This old chestnut is almost completely untrue, and is probably causing lots of people to waste money on lighting. It doesn’t take any more electricity for a light bulb to turn itself back on. If it’s on, it’s using electricity, and if it’s off, it isn’t. Modern low-energy light bulbs do use a tiny amount of extra energy when you first turn them on, as do florescent strip lights, but if you are leaving a room for more than a couple of minutes then it’s still worth turning them off.

Dishwashers use a lot of energy

Myth. In fact, if you do a full load and select a medium temperature on your dishwasher, it can use less energy than doing the washing up by hand. You need quite a lot of hot water to hand-wash the same number of plates. Many dishwashers have an economy setting which will use even less electricity and water.

Cavity wall insulation will make my house damp. The cavity is there to let the walls breathe

Myth. For most people, this isn’t true. Cavity wall insulation is much more likely to solve problems of damp caused by condensation because it makes your walls less cold so less prone to damp. For a few houses that are right on the coast or face persistent driving rain, the empty cavity can provide some protection from damp getting in from outside. This might also be the case if there are cracks or damage in your outer wall. But for the vast majority of people it is well worth getting cavity wall insulation as it will have a big impact on keeping your home warm and reducing your heating bills.

Read more about cavity wall insulation.

My house is old and there is no cavity in the walls so I can’t get them insulated

Myth. There are actually several ways of insulating walls that don’t have a cavity. You can insulate the outside or the inside of the house.

Read our pages in internal solid wall insulation and external solid wall insulation.

The stuff stored in my loft is providing a layer of insulation

Myth. Boxes, packing cases and unused furniture in your loft are not helping to insulate your home. And if they’re squashing your insulation down they’re probably doing the opposite as standard loft insulation works best if it is able to trap lots of air. If you want to store things in the loft, you can get some loft legs to raise the level of the loft boarding to enable you to insulate above the level of the joists, to the recommended depth of 270mm (10.5 inches).

Check out our guide to loft insulation for more great tips.

With warm air heating systems, you should put a bowl of water in front of the vents to stop the air getting too dry

Myth. Some people think that a warm air heating system makes the air in their house dry, and many people put a bowl of water by the vents to moisten the air. There’s no truth in the ‘dry air’ claim, and purposely evaporating water into the air in your home can create problems with damp caused by condensation, so it’s best not to do this. We all release plenty of moisture into the air at home just by washing and cooking.

Discover more about home ventilation on our webpage

Getting double glazing is the best thing I can do to keep the heat in

Classic energy saving myth! People often think that windows are a major problem because they can be draughty and cold draughts are very noticeable. It’s true that double glazing is much better at keeping heat in than single glazing. But, out of the heat you lose from your home, you actually lose about 35% through the walls, about 25% through the roof, and only about 10% through the windows. So getting your loft and cavity walls insulated will make a much bigger difference, and it’s also likely to be far cheaper than getting double glazing.

We’re not saying that double glazing is a waste of money, but it’s better to make sure you’ve insulated the loft and walls first.

Find out more about energy efficient glazing.

Read more on our guide to secondary glazing.

Getting solar panels will mean I never have to pay for electricity again

Myth. Solar panels that produce electricity (known as solar photovoltaics or PV panels) generate electricity that you can use in your own home, which is great. But they only produce electricity during daylight hours. As most PV systems are connected to the grid, there are no batteries to store the electricity for later. So if you are out of the house most of the day and home when it’s dark, you might not use much of your ‘free’ electricity.

Solar PV panels might save you between £75-150 on your annual electricity bill but you’ll still need to use mains electricity from the grid some of the time.

Read more about solar PV.

My clothes won’t get clean at 30C

Myth. You can save a lot of electricity by washing your clothes at a lower temperature. Most washing powders are now designed to work just as well at 30C as they do at higher temperatures. If you are trying to remove a particularly stubborn stain try using a pre-wash stain remover.

LED lights can cause blindness

This myth has been in the newspapers, but light from LEDs is not intense enough to damage your eyes. The most you will experience from LED lights is eye strain or computer vision syndrome – headaches, dizzyness, tired or sore eyes and fatigue caused by excessive screen-time. And this is if you’re looking at the lights for a very long time. If you’re using LEDs in your home there is no need to worry.

It’s not worth turning things off at the plug

Possibly true, depending on the appliance. Leaving TVs, broadband routers, set-top boxes, games consoles and other appliances on standby costs the average household £65 a year according to the Energy Saving Trust. Some appliances cost up to £10 to keep on all year, others just a few pence. ‘Standby savers’ are available that allow you to turn all your appliances off standby in one go.

I have been with my energy supplier for years, so they are probably rewarding my loyalty by giving me a good deal

Sorry, but no. Energy suppliers reserve their discounts and special deals for new customers rather than loyal existing ones. So unless you contact your supplier and ask for a better deal – or suggest you may look elsewhere – you’re likely to be kept on a more expensive tariff. But with the recent price increases, we currently recommend sticking with your current supplier while the market prices are unpredictable.