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.
What a boiler fault code usually means
Modern boilers display a fault code rather than just stopping — the exact code varies by manufacturer, but common causes include low pressure, a faulty sensor, an ignition fault or condensate pipe freezing in cold weather. Note the code and the boiler make/model before calling; it speeds up diagnosis considerably.
How long does heating work take?
A straightforward like-for-like boiler swap is usually a one-day job. Moving the boiler's location, or a full system replacement including radiators, commonly takes 2-4 days. An annual service is typically under an hour.
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.
Frozen condensate pipes in winter
A frozen condensate pipe (the small plastic pipe draining from a condensing boiler, often outside) is one of the most common winter boiler breakdowns — it causes the boiler to shut down as a safety measure. Pouring warm (not boiling) water over the pipe to thaw it, if safely accessible, sometimes fixes this without a call-out.
Heating in older and period properties
Older properties often have narrower pipework, no cavity wall insulation, and sometimes a heating system not originally designed for full central heating throughout — all of which affect boiler sizing and radiator choice. A heating engineer working on a period property will usually assess the whole system, not just swap the boiler in isolation.
Heating emergencies — what to do
If you smell gas, don't use any electrical switches, don't light a flame, turn off the gas supply at the meter if it's safe to reach, and call the National Gas Emergency Service on 0800 111 999 before calling a heating engineer. For no heat or hot water without a gas smell, check the boiler pressure and any error code before assuming a full breakdown.
Why Gas Safe registration is a legal requirement
Anyone installing, servicing or repairing a gas appliance or gas pipework in the UK must by law be on the Gas Safe Register, which replaced CORGI in 2009. This covers boilers, gas fires and gas cookers. Using an unregistered engineer for gas work isn't just risky, it's illegal, and any resulting certificate isn't valid.