Martin Lewis and two energy specialists have addressed the question dividing UK households: is it cheaper to leave the heating on low all day or to turn it on only when needed? On his Money Show Live this week, the personal finance expert was joined by Prof Richard Fitton, Technical Director of Energy House Labs, to explore the issue as temperatures across the country drop.
Energy Savings Trust guidance
Mr Lewis told viewers that the Energy Savings Trust offers a default heating schedule. 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."
He added: "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."
Thermal mass matters
Prof Fitton explained that the best approach depends on the building. 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."
Asked whether such a house should be kept 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."
Smart meters and trials
Prof Fitton noted that households with smart meters, currently installed in roughly 60% of homes, can monitor the difference themselves. He suggested running a two-week trial under each method to see which is more cost-effective, stressing that comparable weather conditions are essential for an accurate result.
Martin concluded: "Heavy house, thermal mass probably better constant. Losing energy probably better just to have it on when you need it."
James Lacey, Director of JLN Plumbing and Heating Ltd, added that the heating system type is crucial: "So depending on the heating appliance that you're using to create heat, it depends how you control it and how you use it." He explained that gas boilers or heat pumps can run at a lower output, making "low and slow" more economical, while oil boilers or electric heaters are either on or off, so time-of-use rates may be better.
