Maintain it · practical guide
The thermostat settings that actually save money
In one line: The DOE-backed numbers for winter and summer, the setback trick worth up to 10% a year, and the heat-pump caveat nobody mentions.
The cheapest home-upgrade of the year costs nothing: three thoughtful numbers on the thermostat. Here are the settings energy agencies actually recommend - and the one equipment type that breaks the rules.
The anchor settings
The US Department of Energy's long-standing guidance: winter, about 68°F (20°C) when you are home and awake; summer, about 78°F (26°C) when home. UK and EU guidance runs the same logic in Celsius - heat to around 18-21°C in lived-in rooms. These are comfort-plus-efficiency anchors, not laws: adjust a degree at a time until your household agrees, and remember sweaters are free.
The setback trick - the real money
The bigger saving is not the daytime number; it is the setback: letting the house drift 7-10°F (about 4-6°C) cooler in winter - or warmer in summer - for the roughly eight hours nobody is home or everyone is asleep. Done consistently, the DOE puts the saving at as much as 10 per cent of annual heating and cooling costs. Every additional degree of setback saves a little more; the total depends on your climate, insulation and how long the setback runs - which is why honest advice gives ranges, not promises. A schedule you set once and forget beats heroic daily adjustments - a smart thermostat automates exactly this, and the payback maths is here.
The heat-pump caveat
Deep setbacks can backfire on heat pumps: recovering the temperature quickly can trigger less-efficient backup (resistance) heat, eating the savings. Many modern heat-pump thermostats manage this intelligently - if your home runs on a heat pump, use its scheduling modes rather than big manual swings. This is also a "check your manual, or ask the installer" moment rather than a rule-of-thumb moment.
The rest of the money is in the house
The thermostat sets the target; the house decides how hard the system works to hit it. Drafts, thin loft insulation and blocked vents inflate every hour of runtime - healthy ventilation keeps comfort honest, a fresh filter is the one-minute maintenance win, and the small always-on loads are worth a meter check too. Set the schedule this evening; the savings start with the very first night.
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General information, not professional advice. Homes differ — if a job is beyond your confidence or the guide’s boundary, that is what tradespeople are for.