Martin Lewis' Money Saving Expert (MSE) website has addressed the recurring question of whether it is better or cheaper to leave the heating on all day, clarifying that there is no single definitive answer.
According to the Energy Saving Trust, 48% of households turn their heating back on in September, while the BBC reports most households are using it again by October. Ahead of the seasonal advice, MSE urged caution on August 26, 2025, stating: “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.”
Energy Saving Trust's Official Guidance
MSE points to the Energy Saving Trust for the 'official answer'. The Trust advises that for households with a boiler—still the majority, though heat pumps are becoming more common—the best approach is to turn the heating on and off rather than leave it on all day.
The Trust 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.”
Heat Pumps and the 'Low and Slow' Method
For those with a heat pump, the advice differs. The Trust added: “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 also highlights the 'low and slow' method, which works best with modern boilers. This involves setting the boiler to a lower constant temperature, such as 18C or 19C, rather than turning it on and off repeatedly. This can help the boiler recover waste heat and operate more efficiently.
Testing What Works for You
Given the complexity, MSE suggests an experiment: “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.”
