Is it best to leave the central heating and hot water on all the time?

I was talking with a friend the other week who said they leave their central heating on all the time because they had been advised it was cheaper. The same applied to their hot water heating system which, “costs much more to heat up from cold than to maintain at a constant temperature”.

We have our hot water on for just half an hour in the morning and half an hour in the evening (we pop it on for an hour if someone’s having a bath) and we have plenty of hot water for our needs. The central heating is also on only when needed, and switched off all day if no one is in.

As I’d often heard the saying that it’s cheaper to leave them on all the time I decided to do some research to find out for sure. During an hour’s researching on the Internet I found a lot of arguments on the subject but eventually found reliable sources that gave a definitive answer.

It’s a common misconception that it’s cheaper to leave them on. The Energy Savings Trust says, “Water heaters use more energy to heat water and maintain a high temperature for an extended period, than they do to heat it up the once.”

The same applies to central heating. Although it uses more energy to heat up a home from “cold” this is a lot less than the energy used keeping the house at a set temperature for long periods when no one is in.

With central heating and hot water systems the most energy efficient method is to use the timer, and set them to come on only when needed.

Related questions

On a similar theme I found an answer to the question, “if I don’t use a particular room should I turn the radiator off in there?

The answer is no. Doing so could cause condensation in this room. The best thing is to fit a thermostatically controlled valve and turn it down low so that it keeps the room aired and prevents it getting too cold.

Which uses the least water, a shower or a bath?

You would think a shower uses less water than a bath and mostly it’s true but it depends how much water you use in your bath and how long you spend under the shower. Especially if using a power shower it is possible to use as much or more water having a lingering shower. If you aren’t sure, put the plug in the bath when next showering and see how much water you actually use.


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What do you think?