Is it more energy efficient to leave the heating on?

This guide is intended to provide general guidance only. It is not intended to give you advice on your personal financial circumstances. You should seek independent professional advice if you’re unsure about anything mentioned in this guide or what choices to make.
It seems logical that the less time you keep your heating switched on, the less it will cost you. However, there is a school of thought that suggests that the energy used to power your heating up from a cold start costs more than leaving it at a level temperature all the time.

So which is the best way to use central heating?

Well, we believe that the most efficient way to heat a house is to programme your heating system so it’s only on when you need it.

Set your heating timer and thermostat so your home is warm when you want it to be – and only then. You could also buy some separate room thermostats and use them to make sure your bedroom’s toasty when it’s time to get up in the morning and your living room’s cosy when you’re watching television in the evening.

That really is the cheapest way to heat a house and keep your home at the temperature you want.

Doesn’t it take a lot of energy to power up a heating system when it’s cold?

Of course it takes a certain amount of energy to kick-start your heating system. However, it also takes energy to keep the heating at a level temperature 24 hours a day.

The idea of leaving heating on all the time doesn’t take into account the fact that some heat is always being lost, even in the best insulated houses.

There's a fundamental principle involved here, which is that the heat loss from a house is always proportional to the difference in temperature between the inside and the outside. So the greater the difference, the more heat you lose. And the longer you maintain that difference (by keeping the heating switched on) the greater the total amount of heat lost - and the more you'll have to pay to replace it.

Even if your home is very well insulated, your heating system will still have to power up at intervals to restore the temperature and replace the heat you've lost.

If your house is poorly insulated, or not insulated at all, the heat loss will be even greater, and the heating could be using energy all the time to maintain a constant temperature. This would work out much more expensive than just turning it on and off when you need it. So it definitely isn’t the most efficient way to heat a house.

If your home isn’t insulated:

  1. 33% of heat is lost through the walls
  2. 26% through the roof
  3. 18% through the windows
  4. 12% is inevitably lost because of draughts and essential ventilation
  5. 11% through the door and the floor

My house is really well insulated, with triple glazing, loft and wall insulation, and draught excluders on every possible gap. Will it still lose heat?

Sorry – yes. Even if you never open your windows, you’ll have to open the door occasionally. You’ll need to drain the water from your basins and bath sometimes. So there will still be a certain amount of heat loss.

However, it’s always worth insulating your home as well as you can. Whether you decide to leave your heating on all the time or turn it on and off, the better your home is insulated, the less energy you’ll need to use – and the lower your energy bills will be.

What about condensation?

It’s true that some people believe that turning the heating on and off throughout the day causes condensation in the walls, which leads to extra heat loss. However, we haven’t seen any conclusive proof of this.

I’m still not convinced – how can I test this theory?

It’s simple. Pick a time when you know you’ll be around for two weeks, and on your normal work/home schedule.

  1. Start by taking a meter reading – from the gas meter if you have a gas boiler, or the electricity meter if you use night storage heaters or electric underfloor heating
  2. For the first week, leave your heating on all the time, at a comfortable temperature – don’t try to prove it’s cheaper by keeping your home cooler than usual
  3. At the end of the week, take another meter reading
  4. For the second week, set your timer and thermostat so your heating goes on and off and only heats your home when you need it – once again, make sure you’re comfortable so as not to skew the results
  5. At the end of the week, take a meter reading

We believe your last meter reading will show clearly that you’ve saved money by switching your heating off when you don’t need it. Whichever the result, you’ll certainly have worked out the cheapest way to heat a house.

Which parts of my home can I insulate?

You can insulate your home’s walls, roof, windows and doors – and of all the things you can do to save energy and reduce your bills, this is the most impactful.

What’s the best way to insulate my home?

These are our favourite ways for preventing heat loss:

  1. Cavity wall insulation is a highly efficient way to stop heat escaping and save money
  2. An adequate thickness of loft insulation should pay for itself many times over
  3. Double or triple glazing will prevent a lot of heat loss, as well as reducing noise and condensation
  4. Buy or make draught excluders for doors and windows– see instructions for a very sweet one here
  5. Get an eco flap to stop warm air escaping through your letterbox
  6. Fill in those draughty gaps between skirting boards and floorboards

If you’re looking into loft or wall insulation for your home, you might be able to get some government help. Find out more here

How can I improve the energy efficiency of my heating and hot water?

Unless your home is brand new, your heating system’s probably not as efficient as it could be.

If your boiler’s 15 years old or more, it could be time to change it for a younger, greener version. Replacing an old G-rated boiler with a new A-rated condensing boiler and a full set of heating controls, including the latest timer and thermostat, could make a big difference to your bills.

In the meantime, keep the heat in your hot water tank for longer by lagging it with a cylinder jacket. You’ll waste less energy heating it, and you could save about £35 a year.

Insulate any hot water pipes you can see in your home – i.e. not the ones in the walls or under the floorboards. Pipes lose heat if they’re out in the open.

You can also buy smart heating controls so you can switch your heating and electricity on and off remotely. Then you can switch on the heating half an hour before you’re due to get home, or switch it off if you’re going to be home later than you thought. This is probably the most cost-effective and best way to use central heating.


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