Three steps to hiring the right heating engineer
First, confirm Gas Safe registration and ask to see the ID card, which lists exactly what gas work they're qualified for. Second, get a written quote naming the boiler model. Third, ask what the manufacturer's warranty requires (usually an annual service) to keep it valid.
Does boiler brand matter?
Established UK brands generally have wider parts availability and more Gas Safe engineers familiar with servicing them, which matters for future repairs, not just the initial install. Ask your engineer which brands they work with most, since familiarity affects diagnosis speed on future call-outs too.
What affects the cost
Cost depends on the type of system (combi vs system vs conventional), whether it's a straightforward swap or a full system change, boiler brand and output size, and property access. Moving a boiler's location, rather than replacing it in place, adds cost because of the extra pipework, flue routing and making good involved.
Combi vs system vs conventional boilers
A combi heats water on demand with no tank or cylinder, suits smaller properties with one bathroom. A system boiler uses a hot water cylinder but no cold water tank, better where several taps might run at once. A conventional (regular) boiler uses both a tank and cylinder, common in older or larger properties, or where mains pressure is poor.
Smart thermostats and heating controls
A smart thermostat can improve control and, for some households, cut heating costs by learning usage patterns and allowing remote control — but it needs to be compatible with your specific boiler and wiring (some older systems need an additional wiring centre). Worth confirming compatibility before buying one separately from your engineer.
What size boiler do you actually need?
An oversized boiler costs more to buy and can run less efficiently; an undersized one struggles with demand, particularly hot water for multiple bathrooms. Sizing should be based on a heat loss calculation for the property and how many bathrooms/hot water outlets are used at once, not just the previous boiler's output copied across.
Red flags in a cheap heating quote
A quote well below others is worth questioning — check it specifies a named boiler make and model (not just "combi boiler"), includes a powerflush if the system is older, and states the warranty length. No Gas Safe registration number offered unprompted is a clear red flag.
Boiler installation certificates, explained
A new boiler installation legally requires a certificate under the Gas Safety (Installation and Use) Regulations 1998, issued by the Gas Safe registered engineer who did the work. You'll need this when you sell the property, and some insurers ask for it if you make a claim involving the heating system.