Martin Lewis's MoneySavingExpert has revealed how to use your central heating Martin Lewis's MoneySavingExpert has revealed how to use your central heating this year. As the temperature continues to drop outside, most of us will have already put the heating on, or be thinking about when to do it. According to experts at the Energy Saving Trust, the idea that it's cheaper to leave the heating on low all day is a myth. Martin Lewis has stepped in and revealed exactly how to use your central heating to get the best value out of it. "Having the heating on only when you need it is, in the long run, the best way to save energy, and therefore money," the website explains.