Not on mains gas? We also install and replace oil boilers. Oil boiler installation
A combi (combination) boiler heats your radiators and your hot water from one unit, taking water straight from the mains and heating it on demand. There is no hot water cylinder and no tank in the loft, which is why it suits most flats and family homes. If you have several bathrooms running at once, a system boiler with a cylinder can be the better choice, and we will tell you which at the survey.
Boiler size is about hot water demand more than house size. For a combi, a home with one bathroom is usually well served by 24 to 30 kW; two bathrooms, or a large bath plus a high-flow shower, point to 30 to 35 kW; several showers used at the same time usually mean a system boiler with a cylinder instead. We size it at the survey from your mains flow rate and pressure, not from a brochure.
A modern gas boiler that is serviced every year typically lasts 10 to 15 years. Past that point repairs get dearer, parts get harder to find and efficiency falls, which is usually when a replacement starts to pay for itself. If your boiler is under ten years old and the fault is a single part, a repair is normally the right call.
For most homes we recommend Ideal or Vaillant. Both carry manufacturer warranties of up to 12 years when installed and serviced by an approved installer, parts are stocked locally, and both cope well with the hard water we have across Hertfordshire and Bedfordshire. The right boiler is the one sized correctly for your hot water demand and fitted with a magnetic filter and a scale reducer; the badge matters less than the installation.
Rarely. The ECO4 scheme runs to 31 December 2026 and almost never funds a like-for-like gas boiler on its own; it funds whole-home packages for households on qualifying benefits. The Boiler Upgrade Scheme (£7,500) is for heat pumps, not gas boilers. Eligibility sits with the schemes, not with installers, so check them directly. For everyone else we quote a fixed price in writing.
Before you choose, read our guides