What questions should I ask about a house's heating system?

Start with the seller's own answers. Guidance for buyers suggests asking how old the current heating system is, how effective it is at keeping the house at a comfortable temperature, and how much the current energy bills are¹. Those three answers frame everything else, because they tie the equipment to the bills actually paid in that house.

Why the heating system matters when viewing a house

A heating system is not a single appliance. It is a boiler or heat generator, an emitter circuit of radiators or underfloor pipework, controls, and often a cylinder, and each part has its own age and condition. A viewing that only looks at the boiler leaves most of the system unassessed.

The practical test is whether the system works now. Independent guidance for movers is blunt: check that the system is running and the house is getting warm⁷. A house that is cold on a viewing day, or where the heating has been switched off, tells you less than one where the radiators are hot and the controls respond.

Where the home is on a heat network rather than its own boiler, the questions change. Heat network customers are advised to check whether the network is part of a consumer scheme like the Heat Trust, which gives more protection if there are problems⁸. Ofgem's research on domestic consumer views found billing transparency is a major user need, building trust in the system and enabling consumers to potentially reduce their costs⁹. For a heat network home, ask who the supplier is, how bills are calculated and what redress exists.

One further distinction matters for independence. An air-to-air heat pump heats air, and an additional system in the home may be needed to deliver hot water¹⁰. A house heated that way is not self-contained for hot water in the way a combi or a cylinder system is.

What to ask about the boiler: age, type and service history

The first question is age. One maker states the average lifespan of a boiler and its central heating system is around 15 years, though this can vary depending on how it is used². Age is not just a replacement cost: it also determines whether grant help is available. The Affordable Warmth Scheme in Northern Ireland applies where a boiler is at least 15 years old¹¹.

The second is type. Boilers are commonly grouped as combi, system or heat only¹². The type decides whether there is a hot water cylinder, whether loft tanks are part of the system, and how the house behaves when the power fails. Ask the seller to name the type and show the installation paperwork.

The third is service history. Annual servicing is recommended so the boiler and system run at their best³. For one maker's standard warranty, the requirement is stricter: at the end of each 12 month period the boiler must be serviced by a Gas Safe registered engineer, and if that condition is not met the boiler warranty will lapse⁵. A missing service record is therefore not just a maintenance gap; it can void cover.

To confirm the exact model and age, the serial number is needed. One maker states it can be found either underneath or on top of the boiler¹³. Photograph it, along with the model badge, so the details can be checked against the manufacturer's records later.

Heating controls and thermostats: what to look for

Controls are where a viewing can be most revealing, because they show how much thought has gone into the system. Independent guidance lists the controls a home should have: a time-controlled programmer, at least one room thermostat, thermostatic radiator valves (TRVs) if there are radiators, and a cylinder thermostat if the system has a hot water cylinder¹⁴.

The regulatory position is firmer than that for new work. Approved Document L Volume 1 requires that, for heating systems in new dwellings, or when a heat generator such as a boiler is replaced in an existing dwelling, each room should be provided with thermostatic room controls able to separately adapt the heating output in each room served¹⁵. The same requirement appears in the edition incorporating 2023 amendments¹⁶ and in the current volume¹⁷. A house with a recent boiler but no room-by-room control has not been brought up to that standard.

Smart controls add remote operation. Most smart heating controls link to a phone, and heating can be controlled via smartphone, tablet or laptop, or by telling a smart speaker what to do¹⁸. That is convenience and oversight rather than independence: the control depends on the maker's app and a working internet connection.

For any control, the operating advice is to consult the manufacturer's manual or your installer for specific advice¹⁴. At a viewing, ask for the manuals and note whether the programmer is legible and set to a sensible schedule.

Insulation and heat loss: questions before you buy

Heat loss determines how much heating a house needs, and the fabric is the part that cannot be changed by swapping a boiler. Guidance on self-build sustainability is direct: insulate walls, roof, and floors to reduce heat loss¹⁹. Independent guidance puts a figure on one element: heat loss through the walls can make up to 35% of all heat loss in the home⁴.

That matters for sizing. When a heating system is replaced or upgraded, it should be sized to suit the reduced level of heat demand, and a lower heat output system is likely to be cheaper to buy and install with lower running costs²⁰. A house that has been insulated may still carry a boiler sized for its pre-insulation heat loss.

For heat pumps the design rules are explicit. A primary heating system containing a heat pump should be selected to meet the full space heating requirement at the design condition chosen for heat loss calculations¹⁷. A low-temperature heating system design must include a heat loss calculation for every heated room²¹. Where a heat pump has been installed in a new dwelling, the operating and maintenance information given to the owner should include the heat loss calculation, the design flow temperature, competent person scheme confirmation, the size of the emitter circuit and minimum set back temperatures²².

Ask the seller for that documentation. If it does not exist, the system's sizing cannot be verified from the paperwork, and a home energy assessment or a retrofit assessment is the route to establishing it.

Running costs and efficiency: what the EPC can and cannot tell you

The EPC is the document buyers reach for first, and it is useful but bounded. It tells you how costly it will be to heat and light the property, and what its CO2 emissions are likely to be, along with cost effective ways to improve the rating and what the rating could be if those improvements were made²³.

Its scope is narrower than many buyers assume. The EPC only considers heating, hot water and fixed lighting, ignoring energy use from kitchen appliances, TVs, computers and any other energy-using devices in your home²⁴. Two identical houses with very different appliance loads can carry the same rating.

The metrics themselves are under reform. The Climate Change Committee has advised that the current EPC rating metrics do not accurately incentivise the energy efficiency and heating solutions required to deliver Net Zero homes²⁵. Its recommended replacement is four primary metrics: total energy use intensity in kWh/m2/yr, space heating demand intensity in kWh/m2/yr, heating system type in categories ranked from 1 to 6, and energy cost intensity in £/m2/yr²⁵.

In Scotland, domestic EPCs will show ratings for heat retention, heating system and energy costs²⁶. That is a more granular presentation than a single band, and it separates the fabric from the system, which is exactly the distinction a buyer needs.

Read the EPC as a starting point, then verify the things it does not cover: the service history, the controls, and the actual bills. The EPC planning guide sets out how to turn the recommendation report into a work list.

Smart meters and tariffs: what to check before moving in

Meters and tariffs are the part of a move that is easy to overlook and awkward to fix later. Guidance for new owners covers finding out who the supplier is, finding the meter and taking a reading, looking into whether to switch energy suppliers, bleeding radiators, learning how to control the heating, and choosing energy efficient appliances⁷.

On smart meters, the position is straightforward. If one has not already been offered, it can be requested from the supplier²⁷. If an issue is suspected, or the supplier identifies one, they should promptly investigate it, resolving it themselves or with third parties and keeping the consumer informed²⁸. Accuracy can be checked by confirming the tariff name, unit rate and standing charge match the bill or contract, and that readings are similar to the meters²⁹.

The tariff question is where smart meters become consequential. A smart meter is needed to get a heat pump or electric vehicle tariff⁶. A household planning either will need one in place.

Economy 7 and Economy 10 need separate attention. Anyone with these systems on radio teleswitch meters will need a new meter to ensure their heating and hot water continue turning on and off as usual³⁰. Ask which meter type is fitted and whether it has been replaced.

Finally, the network. The Distribution Network Operator owns and operates the distribution network of towers and cables that bring electricity from the national transmission network to homes and businesses³¹. It is not the supplier, and it is the body to know for power cuts and supply questions. Where a heat network supplier is also the landlord, they should follow both the authorisation conditions and relevant housing legislation³².