Heating and Heat Pumps, Explained

Heating a home means replacing the heat that escapes through walls, roof, floor, windows and ventilation, and a heat pump does that job by moving heat rather than creating it from fuel. A boiler burns fuel or uses electricity to make heat directly, while a heat pump collects heat from outside air, the ground or water and concentrates it indoors. That difference explains why heat pumps are often discussed alongside insulation, emitter size and controls: the system works best when the home needs less heat and can accept it at a lower temperature.

Think of the whole chain, not just the box on the wall. A stone cottage in a windy valley loses heat differently from a compact new flat, so the same heat source can feel comfortable in one and struggle in the other. This guide is a map of that chain, and the supporting guides take one link at a time.

In practice, heat travels from a source through pipes or ducts to emitters such as radiators or a floor circuit, and a thermostat or weather control decides when it runs. Hot water often shares the same source but follows different rules, because a cylinder must be kept hot enough for everyday use and for hygiene. If one link is weak, for example radiators sized for very hot water, the rest of the system has to work harder to compensate.

A useful habit is to separate three questions: how much heat does this home lose on a cold day, at what temperature can the emitters deliver that heat, and how will the occupants control it room by room. Answering them in that order keeps a conversation with an installer grounded in the home, rather than in a brochure figure.

Before any change, gather the facts that already exist. Find the current EPC or audit, note its date and any assumptions it records, and list the boiler or heat pump model, the emitter types and the controls already fitted. Walk the home on a cold morning if you can and note which rooms lag behind, which radiators stay cool at the bottom, and whether windows show condensation after showers or cooking.

Also note the fuel and electricity arrangements, including meter type and any existing time-of-use tariff, since running costs depend on them. Photograph rating plates and control settings before anyone changes them, so later advice can be checked against what was actually there.

In the EU, the recast Energy Performance of Buildings Directive, Directive (EU) 2024/1275, sets a framework that each member state turns into national law, so phase-out dates for fossil boilers, support schemes and certificate rules are national matters and must be checked in the country concerned. A rule quoted from one member state should never be assumed to apply in another.

In the UK, EPCs, building regulations and installer certification run as a separate system, with differences between England, Wales, Scotland and Northern Ireland. The MCS scheme and TrustMark are relevant to certified installation work in the UK, while EU member states use their own installer and product rules.

A common waste of money is replacing the heat source while leaving undersized emitters and poor controls in place, then running the new system at high temperatures to force comfort. Another is buying a larger unit than the heat loss requires, which can cycle on and off, wear faster and cost more to run. A third is treating a headline efficiency figure as a promise for a particular home, when that figure was measured under test conditions.

Comfort complaints after a change often trace back to settings nobody explained at handover, such as a weather compensation curve left at a default or a timer fighting a room thermostat. Insist on a handover walkthrough and a written note of the settings chosen.

Keep the EPC or audit, the heat loss calculation if one is produced, quotes that state scope in full, product data sheets and the commissioning record together with the home. Those papers let a future assessor, buyer or tradesperson see what was assumed and what was actually installed.

Ask a qualified installer: what heat loss did you calculate for this home, what flow temperature did you design for, which controls will manage each zone, and what maintenance and checks will this system need each year. Clear answers to those four questions are a good sign; vague ones are a reason to pause.