For most homes, heating only when you need it is cheaper. The exception is a badly insulated house with a damp or condensation problem, where steady low background heat can be worth it for reasons other than the bill.
- The physics: a house loses heat in proportion to the difference between inside and outside. Keeping it warmer for longer means losing more heat overall, so timed heating uses less energy.
- The practical exception: in a poorly insulated house that cools very fast, reheating from cold takes a long time and the cold surfaces attract condensation and mould. Low steady heat can be the cheaper option once you count the damp.
- What definitely works: turning the thermostat down by one degree, which is worth several per cent, and using thermostatic radiator valves to heat only the rooms in use.
- Do not turn the boiler flow temperature up to heat faster. On a condensing boiler it makes it less efficient.
Never turn the heating off completely in winter in an empty house. Frozen pipes burst when they thaw, and that is an insurance claim rather than a saving. Leave it on frost protection.
Heat loss is driven by the temperature difference across the walls. Less time at a high difference means less total energy, which is why the timer usually beats the thermostat left on low.
Energy figures are worked from the Ofgem price cap on the date shown and from typical power for the appliance class, not from a named model. Your own rate and your own rating plate are the ones that count. Full disclaimer.