Oil-fired boilers, what's different
Oil boilers are common in properties off the mains gas network, need an oil storage tank with its own maintenance and safety considerations, and are serviced by OFTEC-registered engineers rather than Gas Safe (which only covers gas). If you're off-grid, confirm your engineer's OFTEC registration specifically.
How long should a boiler last, and when to replace vs repair
Most boilers last 10-15 years with regular servicing. As a rough guide, if a repair would cost more than a third of a new boiler's price, or the boiler is over 10-12 years old and parts are getting harder to source, replacement is usually the better long-term value than another repair.
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.
Understanding the labour vs materials split
The boiler itself is often the largest single cost, but labour, flue work, and any additional pipework or radiator changes add up. If a quote looks cheap, check it specifies the same boiler tier (entry-level vs mid-range) as a competing quote, not just a lower labour charge.
Boiler warranties and workmanship guarantees
Manufacturer warranties on new boilers commonly run 5-10 years, but usually require annual servicing by a registered engineer to stay valid — check whether it has to be the same installer or any Gas Safe engineer. This is separate from any workmanship guarantee the engineer offers on their own installation work.
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.
When to replace vs keep existing radiators
Radiators themselves rarely need replacing unless damaged, corroded, or you're changing the property's heat demand (e.g. adding a heat pump, which often needs larger radiators to run at a lower temperature). A power flush can often extend a radiator's working life significantly cheaper than replacement.
Carbon monoxide safety
A carbon monoxide alarm should be fitted near any gas appliance, and tested regularly like a smoke alarm. Signs of a potential CO issue include a yellow/orange (rather than blue) gas flame, soot marks around an appliance, or unexplained headaches/nausea that ease when you leave the property — treat these as urgent.