Guide
Annual generator maintenance cost: what you are paying for
Updated
Two quotes for servicing the same standby set can differ threefold and both be honest. The difference is almost always scope, not labour cost.
Why there is no honest average
Servicing covers everything from oil and filters on a small standby set to an annual regime on a critical installation, with load bank testing, fuel sampling and transfer switch proving.
Of 58 UK generator service providers whose pages we could read, 3 publish a service price. They charge £250, £265 and £275 for a standard diesel set service, a median of £265, read on 12 October 2026. The other 55 publish nothing and are recorded as not published.
Those are entry prices for small and mid-size sets; the highest covers any diesel generator up to 500kVA, plus VAT. A large set, load bank testing and fuel work cost more. Every row and its source is in the UK Generator Service Price Index.
The scope questions that explain the gap
- Is load testing included? A service that runs the set off-load for twenty minutes is a fraction of the cost of one that proves the set under load. Both get called an annual service.
- Is fuel in scope? Sampling, polishing and tank cleaning are separate jobs and often the biggest surprise on inherited plant.
- Are consumables included or extra? Oil, filters, coolant, batteries and belts. Ask which are in the price and which are quoted on condition.
- Is the transfer switch covered? Proving an automatic changeover on simulated mains failure involves the electrical installation and someone authorised to switch.
- What is the response promise? Response cover is a separate purchase from planned maintenance, and it is where contract prices really diverge.
What annual generator maintenance costs in a year
The annual cost is the price of a service times the visits your manufacturer's schedule and hours run call for. On top come load bank testing, fuel sampling or polishing, batteries and consumables, and any response cover.
One provider in the index, Generators AS in the South West, also publishes annual plans (Generators AS service pricing, read 30 October 2026):
- A standby set, Service A and Service B six months apart: £495 a year up to 50kVA, £660 for 101 to 250kVA and £1,145 above 900kVA.
- A single Service A: £265 to £825.
- A set on prime power: serviced every 250 to 400 hours and priced per visit, from £239 a visit up to 50kVA when three or more are pre-booked.
How to make quotes comparable
- Send the same information to everyone. Engine and alternator make and model, kVA rating, hours run, fuel tank size, site access and permit requirements.
- Ask for a price per set with a task list. Not a site total, and not a service tier name without contents.
- Ask for labour rates separately. Standard hours, out of hours, callout, and travel. That is what breakdowns will actually cost you.
- Ask what the report contains. Readings, not ticks, and a dated list of recommended work with priorities.
The cheapest annual service is usually the one that proves the least. If the set exists to protect something expensive, buy the test that proves it works, not the visit that proves it starts. See load bank testing.