The questions British homeowners actually ask about a new boiler.

Combi or system boiler, and does it matter for a heat pump later?

For most British homes with one bathroom, a combi remains the simpler and cheaper answer. The decision starts to swing toward a system boiler when there are two bathrooms in regular use or when a hot-water cylinder is desirable for solar diversion or a future heat pump. If a heat-pump retrofit is plausibly on the horizon, retaining a cylinder loft is genuinely useful, since most heat-pump installs need a buffer or unvented cylinder anyway.

How big a boiler do I actually need?

Most UK 3-beds need a 24 to 30 kW combi for hot water, with the heating output modulating down to around 6 kW. Oversizing has been the industry default for two decades and is a meaningful contributor to short-cycling, premature wear and inflated bills. Ask the installer to show you a heat-loss calculation, not a rule of thumb based on the number of radiators.

Are 10-year boiler warranties really 10 years?

Almost always, yes, but only if the boiler is registered by a manufacturer-accredited installer within thirty days and is serviced annually. Miss either condition and the warranty typically reverts to two years. The cost of an annual service is small compared with the value of the warranty being intact when something fails in year eight.

A boiler in 2026 is mature kit. The household that pays attention to sizing, controls and the annual service quietly gets twelve good winters out of it, regardless of which brand sits on the wall.