Temporary power

Generator running costs for events — what to budget

Running cost.

Generator cost is not only the hire or purchase price. The real number comes from fuel, run hours, load level, servicing, refuelling, and how often the set is running when the site does not need its full output.

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What matters

Five inputs drive the number — and they are the same inputs that decide when battery and hybrid event power works out cheaper than running a generator alone.

Load percentage

A generator rarely uses fuel in a straight line. A lightly loaded diesel set can still burn a meaningful amount of fuel, while a well-loaded set often gives a better cost per kWh. For planning, use the manufacturer fuel curve at 25%, 50%, 75%, and 100% load where available. The Temporium calculator includes verified Atlas Copco QAS example curves, but the exact generator on your site should still be checked before a quote is confirmed.

Run hours

Daily run hours are often the biggest cost driver. A generator used for a short event load has a different cost profile from a welfare or site setup that runs all day, every day, for a season.

Diesel price

Use the latest pump price as a starting point, then adjust for delivered fuel, storage, refuelling labour, and any site-specific handling cost. The Temporium calculator uses the official UK weekly road fuel price where available, with a manual override.

Source quality

A manufacturer datasheet is better than a generic estimate. Retail listings and hire sheets can still help with early planning, but the safest workflow is to keep the calculation editable and attach the source to the enquiry.

Service allowance

Maintenance is easy to ignore in a quick quote. Add a service allowance per hour if you are comparing generator-only running against a battery-supported system.

Common questions

FAQ

What drives generator running cost?

Fuel use (a function of load percentage, run hours and diesel price), servicing, and idle or low-load hours — not just the headline hire rate.

Why does low-load running cost more?

A generator at low load burns fuel inefficiently and wears faster, so the cost per useful kWh climbs. Right-sizing the unit, or adding a battery to cover light loads, avoids it.

How do I cut generator fuel cost?

Right-size the unit to the real load, cut idle hours, and add battery or hybrid storage to cover light, quiet and overnight loads so the generator runs less.

Diesel or battery — which is cheaper?

It depends on load and run hours: for long, high, sustained loads diesel can win; for quiet or variable loads a battery or hybrid usually does. The running-cost calculator compares them for your case.