Money guru Martin Lewis’ Money Saving Expert website has set the record straight on the great heating debate and whether it’s better or cheaper to leave the heating on all day. Every year around this time, people start trying to work out when to put the heating back on. According to the Energy Saving Trust, 48% of households will put the heating on again in September, while the BBC reports that most households are using the heating again by October.
But just before all sorts of advice began to fly around at this time of year about when to turn your heating on, and whether to leave it on all day or turn it on and off as needed, Martin Lewis’ MSE set the record straight about the ‘definitive’ answer – or the lack of one.
MSE pleaded, on August 26, 2025: “We wish we could give you a definitive answer, but this question is far more complex than it first seems, and we’re not heating engineers or physicists. So please ignore clickbait publications erroneously crediting Martin with an answer – he knows a lot (too much) about energy bills, but this one isn’t his or our bag.
“Ultimately, there are arguments for and against it, and it’ll likely depend on the type of heating system, your usage pattern, and what type of home and insulation you have.”
The ‘official answer’, MSE says, comes from the Energy Saving Trust.
The Trust says that if you have a boiler (and most still do, even though heat pumps are becoming more common), then the best thing to do is turn your heating on and off, NOT leave it on all day.
It said: “If you have a boiler, then no – keeping your heating on all the time will use more energy and cost you more money.
“It’s more energy efficient, and better for your bills, to have your boiler come on when you need it.”
But if you do have a heat pump, then leaving the heating on all day is better. It adds: “But if you have a heat pump, then you can save money by leaving the heating on all day. Check out our advice on how to improve your heat pump’s efficiency.”
MSE points to the ‘low and slow’ method, which works best with modern boilers. Here, you set the boiler to a lower constant temperature rather than turning it on and off all the time. Setting it to 18C or 19C and then leaving it on constantly can help the boiler to recover waste heat and operate more efficiently.
MSE adds: “So perhaps the best advice is to try an experiment. Try a few days or a week with your heating on a constant low setting and then try only having the heating come on as and when you need it over the same time period and compare the energy use.
“Take meter readings at the start and end of each period and compare.”
