Quick answer
A 60 kVA diesel generator typically uses about 4.5 to 5 litres an hour at 25% load, 7.3 to 8.7 at 50%, 10 to 12.6 at 75% and 13.5 to 16 at full load. For a standby set running around half load, plan on roughly 7 to 9 litres an hour, which is about 175 to 210 litres over 24 hours.
This guide sets out litres per hour at each load, how long a tank lasts, what it costs and how to bring the number down. It is part of a three-part series. For sizing, see what a 60 kVA generator can run.
60 kVA generator fuel consumption chart
The first column below is taken from the manufacturer's published data sheet for the Cummins C66 D5e, the engine family behind our Cummins C66D5EQ and Cummins C66D5e. The second shows the range across published data for 60 kVA sets from several makers, including hire fleets.
| Load | Output (prime, 48 kW) | Cummins C66 D5e, prime | Typical range, 60 kVA sets | |---|---|---|---| | 25% | About 12 kW | 4.5 litres per hour | 4.5 to 5 litres per hour | | 50% | About 24 kW | 7.3 litres per hour | 7.3 to 8.7 litres per hour | | 75% | About 36 kW | 10.6 litres per hour | 10 to 12.6 litres per hour | | 100% | About 48 kW | 14 litres per hour | 13.5 to 16 litres per hour |
At the standby rating of 66 kVA (53 kW), the same Cummins data shows 4.8, 7.8, 12 and 16.2 litres an hour at 25, 50, 75 and 100% load. Standby ratings are for emergency use only, so plan around the prime figures if you will run the set often. Always check the datasheet for the exact model you are buying, because engines, alternators and tuning differ.
What does that cost per hour and per day?
The table below uses an illustrative diesel price of £1.50 a litre. Replace it with your own price.
| Load | Litres per hour | Cost per hour | Litres per 24 hours | Cost per 24 hours | |---|---|---|---|---| | 25% | 4.5 | £6.75 | 108 | £162 | | 50% | 7.3 | £10.95 | 175 | £263 | | 75% | 10.6 | £15.90 | 254 | £382 | | 100% | 14 | £21.00 | 336 | £504 |
How long will a tank last?
Run time is tank size divided by litres per hour. Our Cummins C66D5EQ has a 200-litre tank and the C66D5e has 180 litres. These figures use the full nominal capacity, so allow around 10% less in practice to keep a reserve.
| Load | Litres per hour | 180-litre tank | 200-litre tank | |---|---|---|---| | 25% | 4.5 | About 40 hours | About 44 hours | | 50% | 7.3 | About 25 hours | About 27 hours | | 75% | 10.6 | About 17 hours | About 19 hours | | 100% | 14 | About 13 hours | About 14 hours |
If you need longer autonomy, ask about larger base tanks or an external fuel supply. Note that the Control of Pollution (Oil Storage) (England) Regulations 2001 apply to business oil storage containers of 201 litres or more, so a larger tank may bring secondary containment requirements into play. The GOV.UK guidance on storing oil explains when the rules apply, and the Environment Agency can advise on specific cases.
Why light loads waste fuel
A diesel generator is most efficient at moderate to high load. Using the Cummins figures against the generator's output, fuel use per kilowatt-hour looks like this:
- 25% load: about 0.38 litres per kWh
- 50% load: about 0.30 litres per kWh
- 75% load: about 0.29 litres per kWh
- 100% load: about 0.29 litres per kWh
So a set running at 25% burns around a third more fuel for every kilowatt-hour it delivers than one at 75%. Running lightly loaded for long periods also risks wet stacking, where unburnt fuel builds up in the exhaust and the engine glazes. As a guide, aim to keep the load between about 40% and 80%.
> Expert tip: If your generator mostly runs at under 30% load, it may be oversized. Check your real load before you buy. Our guide to what a 60 kVA generator can run shows how to add up a realistic list.
What changes a generator's fuel use?
- Load. The biggest factor by far, as the chart shows.
- Engine condition and servicing. Worn injectors, blocked filters and old oil all raise consumption.
- Fuel quality. Clean, correct-grade diesel and a tidy tank protect the injectors.
- Ambient temperature and altitude. Hot, thin air reduces efficiency slightly.
- Rating. The same engine burns more at a higher standby rating than at its prime rating.
- Unbalanced or poorly matched loads. Heavy single-phase loads on one phase can force the set to work harder than the total suggests.
- Idle running. A generator left running with almost no load still burns fuel.
How to measure your own consumption
- Fill the tank to a marked level and note the running hours on the meter.
- Run the generator on its normal load for a set period.
- Refill to the same marked level and note the litres added.
- Divide the litres by the hours run to get litres per hour.
- Compare it with the datasheet. A figure well above it points to a service issue or an unusual load.
Ways to reduce fuel use
- Match the set to the load, so it runs at 40 to 80% most of the time.
- Keep to the service schedule, including fuel and air filters.
- Avoid idling the generator when no load is connected.
- Use a load bank test where a standby set rarely carries load.
- Switch off non-essential equipment during outages.
Our guide to fuel saving methods for generators goes into more detail on load management and tank care.
What does a year of running cost?
At £1.50 a litre, using the Cummins figures:
- Standby set, 50 hours a year at half load: about 365 litres, or roughly £550.
- Heavier standby use, 200 hours a year at half load: about 1,460 litres, or roughly £2,190.
- Regular prime use, 2,000 hours a year at 75% load: about 21,200 litres, or roughly £31,800.
For purchase prices and the other features of the product, see our 60 kVA generator webpage.
> Want help working out your running costs? Send us your load and expected running hours and we will estimate consumption for a set from stock. Use the contact page or call +44 1302 700200.
Frequently asked questions
How much fuel does a 60 kVA generator use per hour?
About 4.5 to 5 litres at 25% load, 7.3 to 8.7 at 50%, 10 to 12.6 at 75% and 13.5 to 16 at full load, depending on the make and model.
How much diesel does a 60 kVA generator use in 24 hours?
Around 175 litres at half load and about 254 litres at 75% load, based on Cummins data. At full load it is closer to 336 litres.
How long will a 200-litre tank last on a 60 kVA generator?
Roughly 27 hours at half load, 19 hours at 75% load and 14 hours at full load, using nominal tank capacity. Allow a reserve in practice.
Is a 60 kVA generator more efficient at full load?
Per kilowatt-hour, yes. Efficiency is best between about 75% and 100% load and worst below 30%. In practice, aim for 40 to 80% to balance efficiency with headroom.
Does a 60 kVA generator use more fuel at its standby rating?
Yes. At full load the Cummins C66 D5e data shows 16.2 litres an hour at its 66 kVA standby rating, against 14 litres an hour at its 60 kVA prime rating.
Do I need a permit to run a 60 kVA generator for long hours?
Environmental permit rules apply to medium combustion plants and specified generators, which are much larger than a 60 kVA set. You can confirm the thresholds in the GOV.UK guidance on medium combustion plants and specified generators.
Conclusion
A 60 kVA diesel generator uses roughly 7 to 9 litres an hour at half load and up to 14 to 16 at full load. The best way to control fuel cost is to size the set properly, keep it serviced and avoid running it lightly loaded for long periods. Work out your real load first, then check consumption against the datasheet for the exact model.
> Talk to a real person: Global Generators is an authorised Cummins reseller and an authorised Grupel and Pramac dealer, with new diesel generators in stock for UK delivery and export. Browse our full 60 kVA generator range, or contact our team on +44 1302 700200 or at enquiries@global-generators.com and we will help you match a set to your load.