How much diesel does a generator use?
A rough rule: a diesel generator burns about 0.07 gallons an hour per kilowatt of load. Here is what that means for each rental size.
Updated 2026-10-16
Fuel by size
| Size | Gallons / hour at ¾ load | Gallons / day around the clock | Tank | Hours on a tank |
|---|---|---|---|---|
| 20 kW | ~1.4 | ~34 | ~60 gal | ~43 |
| 36 kW | ~2.4 | ~58 | ~70 gal | ~29 |
| 56 kW | ~3.6 | ~86 | ~100 gal | ~28 |
| 100 kW | ~6.8 | ~163 | ~180 gal | ~26 |
| 150 kW | ~10 | ~240 | ~220 gal | ~22 |
| 200 kW | ~14 | ~336 | ~300 gal | ~21 |
Typical figures for the class. Actual use depends on the load, the altitude and the heat.
Planning fuel for your run
- One shift a day (8 hours): most tanks last two to four days. Refill at the end of the week or let the yard add it at pickup.
- Around the clock (an outage, a standby): a tank lasts one to two days. Plan a refill or a fuel service from the start.
- Weeks on a job site: an external double-wall tank stretches a refill to a week or more.
What fuel costs
At around $5 a gallon, a 56 kW unit on one shift at three-quarters load uses about 29 gallons a day — roughly $145 a day in fuel. Around the clock, about $430. That is often more than the rent, so sizing right matters for the fuel bill as much as for the rental.
Questions
Does a generator burn less fuel at a light load?
Yes, but not proportionally. At a quarter load a diesel burns roughly a third of its full-load fuel, not a quarter, and a long run at very light load causes wet-stacking. Size the generator so it works at half to three-quarters load.
Who refuels the generator?
For short rentals, you can; the yard bills any diesel it adds at pickup. For long or around-the-clock runs, we add a fuel service that tops it up on site, or an external tank.
Can I use biodiesel?
Most rental units require ultra-low-sulfur diesel only. Ask before you put anything else in the tank.
Want the size worked out for you?
Send the list of what has to run and the address. We text you back with the size, one all-in price and a delivery day.