A gas boiler should be serviced once every 12 months.

Here’s why annual servicing is recommended:

• ✅ Safety – Checks for gas leaks, carbon monoxide risks, and proper ventilation.

• ✅ Efficiency – Keeps the boiler running smoothly, which can reduce energy bills.

• ✅ Reliability – Prevents unexpected breakdowns, especially before winter.

• ✅ Warranty & insurance – Many manufacturers and insurers require yearly servicing to keep cover valid.

• ✅ Legal requirement (landlords) – If you rent out property, you must arrange a Gas Safety Check (CP12) every year by law.

The efficiency of your gas boiler depends on its age, type, and condition:

• Modern condensing boilers (less than 15 years old) – typically 90–94% efficient when working properly.

• Older non-condensing boilers (15–25 years old) – often only 70–80% efficient.

• Very old boilers (25+ years) – sometimes 60–65% efficient or less.

A service doesn’t magically turn a 70% boiler into a 90% one, but it can restore lost efficiency and stop it wasting fuel. For example:

🔧 How a service improves efficiency:

• Flue and combustion check – ensures the gas is burning cleanly, avoiding wasted energy.

• Cleaning heat exchanger & burners – removes soot and scale that insulate surfaces, allowing more heat to transfer into your water.

• Checking system pressure & expansion vessel – keeps water circulating properly so heat is delivered efficiently.

• Seals and safety devices – prevent gas or heat loss.

• Advice on controls & settings – engineers often optimise timers, thermostats, or flow temps to save money.

In practice, a service might improve efficiency by 2–5% on a relatively modern boiler, and much more on a neglected one. The bigger win is that it prevents breakdowns and keeps the boiler safe.

Your gas boiler should only ever be serviced by a Gas Safe registered engineer.

Here’s what that means in practice:

• 🔎 Gas Safe Register – This is the official UK body that replaced CORGI. Every legal engineer working on gas appliances must be on this register.

• 🪪 ID Card – A Gas Safe engineer will have a yellow ID card. On the back, it shows exactly what types of work they’re qualified to do (e.g. boilers, cookers, fires).

• 🏠 Domestic vs commercial – If you’ve got a normal home boiler, you need someone qualified for domestic gas appliances. Larger boilers in businesses may need a commercial ticket.

• ⚖️ Legal requirement – For landlords, it’s the law to use a Gas Safe engineer for the annual check and Gas Safety Certificate (CP12). For homeowners, it’s not a legal requirement, but strongly recommended for safety and warranty reasons.