Guide
Generator maintenance contracts: what to put in one
Updated
A generator contract is three purchases in one wrapper: planned visits, response cover and evidence. Price them separately or you cannot compare two proposals.
The three things you are buying
- Planned maintenance
- Visits at agreed intervals with a defined task list, to the manufacturer's schedule on hours and calendar. This is the part that is easy to price and easy to compare, so long as the task list is attached.
- Response cover
- A promise about how quickly an engineer attends when the set fails or is needed. This is where prices really differ, and where the wording matters more than the number.
- Evidence
- Reports, readings, load test results, fuel sample results and a maintenance log kept up to date. PUWER expects the log; your insurer, auditor or client may expect more.
An annual maintenance contract for a diesel generator
An annual maintenance contract, often called an AMC, is the planned part priced for a year. It sets a number of visits to the manufacturer's schedule, each with its task list, and usually one fuller annual service.
For a diesel generator the schedule is driven by hours run as well as the calendar. A set that runs often needs more visits than a standby set that barely runs. Ask for the visit count, the tasks at each visit and the annual price, and treat response cover as a separate line.
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.
The service level agreement: clauses worth arguing about
- Response measured from when? From your call, not from when the engineer is dispatched, and with a defined out-of-hours route that a human answers.
- Parts availability. A four hour response with a three week part is not cover. Ask what is held in stock for your engine.
- What counts as covered. Whether consumables, batteries, coolant and filters are included, and whether repairs found at service are inside the contract or quoted separately.
- Load testing and fuel work. Both are commonly excluded from the headline contract price. Decide whether you want them in, then compare on the same basis.
- Escalation and exit. Annual uplift mechanism, notice period, and what happens to your records when you leave.
Getting comparable proposals
- Write a one page specification. Sets, ratings, engine and alternator makes, hours, what they protect, access constraints, and the visits and tests you want.
- Ask every provider to price that specification, plus a separate optional list for anything they think is missing.
- Ask for the standard and out-of-hours labour rates even under contract, because that is what non-contract work will cost.
- Ask for a sample service report. If the sample is a page of ticks with no readings, you now know what you would be filing for the next five years.
A contract does not transfer your duty. PUWER duties sit with the employer who controls the work equipment, and buying maintenance does not move them. What a good contract does is make the duty easy to discharge and easy to evidence.