Martin Lewis has weighed into the debate over whether households should leave their heating on low all day or turn it on only when needed, with the answer depending on the type of home and heating system.
On his Money Show Live this week, Lewis spoke to Prof Richard Fitton, Technical Director of Energy House Labs, and James Lacey, Director of JLN Plumbing & Heating Ltd, to settle the question as temperatures across large parts of the UK dropped below zero overnight.
Energy Savings Trust default guidance
Lewis told viewers that the Energy Savings Trust has a default setting for heating schedules. He said: "The Energy Savings Trust default setting is that you have your heating on from 7am to 9am in the morning. This is for people who go out to work during the day, not people who are staying at home all day.
"You have your heating on from 7am to 9am in the morning and then you have it on from 4 to 11 at night. And that should keep the fabric of your house going. And generally the rule is you only pump heat into your house when you need it."
How home type affects the answer
Prof Fitton explained that the best approach depends on the building's construction. He said: "It depends on a number of things. The weather that the type of building, if you've got a big heavyweight house with lots of thermal mass, and that might be a solid brick Victorian terrace for instance, that kind of then that will store heat and that will act as a battery for heat.
"Whereas, if you have a very light lightweight or modern house made of timber frame for instance that will heat up really quickly but won't necessarily store the heat."
Lewis clarified: "So the first one you have it on low all day?" Prof Fitton replied: "They can work in different ways but I think that's probably an easier challenge for that house."
Testing with smart meters
Prof Fitton noted that about 60% of homes now have smart meters, which allow people to check the impact of their heating habits. He said: "You can literally do your own experiment. Put me out of a job. Do your own scientific experiment and see which works out best for you."
They suggested running an experiment for two weeks each way to see which approach costs less, but stressed that the overall weather temperature should be similar for a proper comparison.
Lewis summed up: "Heavy house, thermal mass probably better constant. Losing energy probably better just to have it on when you need it."
James Lacey added that the type of heating appliance also matters. He said: "So depending on the heating appliance that you're using to create heat, it depends how you control it and how you use it. So if you're on a say a gas boiler or a heat pump that you can modulate out its output and run it a little bit lower or slower, then that's it's steady state heating. Low and slow is going to be more economical, better for your bills.
"But if you're on say an oil boiler or some electric heaters, they're either on or they're off. They haven't got a low. So they're going to be cycling on and off. And in them cases, you're probably better off using at the time traditional sort of time of use rates."
