Boiler service: what it costs and what actually gets checked

A boiler service is one of the cheapest things you will ever pay a Gas Safe engineer to do, and it takes thirty to forty-five minutes if it is being done properly. Prices vary by area, so ask two local firms rather than trusting a national figure.

What a real service includes

A flue gas analysis - the engineer puts a probe in the flue and reads the combustion. This is the test that matters, because it is the one that catches incomplete combustion and therefore carbon monoxide.

Visual inspection of the heat exchanger, burner and seals. A check of the gas pressure and flow. A check of the safety devices. A pressure and flow test of the system. The condensate trap cleared. The casing removed and the inside actually looked at.

What a bad service looks like

Twelve minutes, casing never off, a look at the pressure gauge, a certificate. If nobody put a probe in your flue, you have not had a service - you have had a visit.

You are entitled to ask what was checked, and a good engineer will tell you without getting defensive.

Why it is not optional

Almost every manufacturer warranty requires an annual service by a Gas Safe registered engineer, recorded in the benchmark book. Skip one, and a heat exchanger claim in year seven gets refused - and the heat exchanger is the most expensive part in the boiler.

A service costs a fraction of what a failed heat exchanger does, and a fraction again of what the warranty is worth. That is the whole argument.

If you are a landlord

You need a Gas Safety Certificate (CP12) every twelve months, by law, and a copy must go to your tenant within 28 days. That is a legal duty under the Gas Safety (Installation and Use) Regulations 1998, not a suggestion. A service and a CP12 are not the same thing, though most engineers will do both in one visit.