Martin Lewis has issued a heating warning to households facing winter bills, as the debate over whether to leave the heating on all day or only switch it on when needed continues. The Money Saving Expert team has stressed there is no straightforward answer to the question, despite claims online suggesting otherwise.
In advice published by the website, it said: “We wish we could give you a definitive answer, but this question is far more complex than it first seems.” Whether it is cheaper to keep the heating running at a low temperature or turn it on and off depends on several factors, including the type of heating system, how often a home is occupied and how well it is insulated.
Energy Saving Trust advice
The Energy Saving Trust, the UK's main public body for reducing energy use and carbon emissions, says leaving the heating on all day generally uses more fuel because more heat escapes from the property. Its advice is to heat a home when it is needed rather than continually pumping warmth into empty rooms.
The organisation's approach is simple: “Pump heat into your home when you need it; don't pay to keep pumping it when you don't.” Using a timer alongside a thermostat can help households maintain a comfortable temperature without wasting energy.
Heat Geek's 'low and slow' method
However, heating specialists Heat Geek argue that the answer can be more complicated, particularly for homes with modern boilers or heat pumps. They suggest a method known as “low and slow”, which involves keeping the heating at a lower, steady temperature rather than repeatedly switching it on and off.
For some households with a modern condensing boiler or heat pump, maintaining a temperature of around 18C or 19C could be more efficient, particularly if people spend much of their time at home. Heat Geek says running a system at a lower flow temperature, the temperature at which water is sent to the radiators, can also help it operate more efficiently. But this approach will not suit everyone.
Factors that affect the choice
Households where occupants are out for most of the day may find keeping the heating running wasteful, while the construction of a property can also make a difference. Modern homes with plasterboard walls can warm up more quickly, potentially making it practical to switch the heating on only when needed. Older brick properties may take longer to heat up but can retain and release warmth for longer.
The type of heating also matters. Traditional radiators may be better suited to being switched on and off, while underfloor heating can work more effectively when maintaining a consistent temperature. Insulation is another important consideration. Homes with good cavity wall and loft insulation are likely to lose less heat, which could make a low-and-slow approach more suitable.
Money Saving Expert acknowledged that the competing advice can be frustrating for households looking for a definitive way to cut their bills. It admitted: “Sadly there doesn't seem to be a firm answer.” Instead, it recommends experimenting with both approaches and comparing the results.
Households could try keeping their heating at a constant low temperature for several days or a week, then compare this with a similar period when the heating is only switched on when required. Taking meter readings at the beginning and end of each period can help show which method uses less energy. However, the comparison may be affected by the weather, as a particularly cold week could require more heating than a milder one.
