How much fuel is your generator burning?
Enter your generator's rated output in kW, the load it runs at and your diesel price. The rates are approximate medians from 28 manufacturer spec sheets; the generator fuel consumption chart has the figures by model.
Example: the EIA U.S. average for on-highway diesel, week of Oct. 12, 2026 ($6.179). Enter the price you actually pay; dyed off-road diesel is usually lower because it carries no federal excise tax when used off-road.
Running a large generator fleet?
FuelGo delivers diesel to generators nationwide. Dispatch runs 24/7/365, and a dispatcher replies within the hour.
📞 Call 800-720-4546
How much fuel does a generator use?
Diesel generator fuel use comes down to two numbers: rated output (kW) and load, the share of that rating the set is actually carrying. Across 28 Cummins, Cat, Generac and Kohler spec sheets, the median burn is about 0.074 gallons per hour per kW at full load, 0.059 at 75%, 0.042 at 50% and 0.022 at 25%.
Per kWh actually produced, that's about 0.074 gallons at full load, 0.079 at 75%, 0.083 at 50% and 0.089 at 25%. These are approximate medians; your spec sheet has the exact figure. The generator fuel consumption chart lists gallons per hour by model from 20 kW to 2,000 kW.
Fuel consumption by load level
Fuel burn doesn't fall in step with load. On the spec sheets, a set at 25% load still burns roughly 30% of its full-load fuel, so every kWh costs more: about 0.089 gallons per kWh at 25% load against 0.074 at full load. That's why an oversized generator is expensive to run.
Light loading is also hard on the engine. NFPA 110 requires emergency sets to be exercised monthly for at least 30 minutes at no less than 30% of nameplate kW, or at a load that reaches the maker's minimum exhaust temperature, because long light-load runs cause wet stacking.
| Generator size | Typical application | 25% load | 50% load | 75% load | 100% load | Daily cost (75%, 8 hrs, example $6.18/gal) |
|---|---|---|---|---|---|---|
| 20 kW | Small office, retail | 0.4 gal/hr | 0.8 gal/hr | 1.2 gal/hr | 1.5 gal/hr | $58 |
| 30 kW | Mid-size commercial | 0.7 gal/hr | 1.3 gal/hr | 1.8 gal/hr | 2.2 gal/hr | $88 |
| 60 kW | Large commercial, events | 1.3 gal/hr | 2.5 gal/hr | 3.5 gal/hr | 4.4 gal/hr | $175 |
| 100 kW | Construction, telecom | 2.2 gal/hr | 4.2 gal/hr | 5.9 gal/hr | 7.4 gal/hr | $292 |
| 150 kW | Data center, hospital backup | 3.3 gal/hr | 6.3 gal/hr | 8.8 gal/hr | 11.1 gal/hr | $438 |
| 200 kW | Large industrial | 4.4 gal/hr | 8.4 gal/hr | 11.8 gal/hr | 14.8 gal/hr | $583 |
| 500 kW | Campus, large facility | 11.0 gal/hr | 21.0 gal/hr | 29.5 gal/hr | 37.0 gal/hr | $1,458 |
| 1,000 kW | Utility, major industrial | 22.0 gal/hr | 42.0 gal/hr | 59.0 gal/hr | 74.0 gal/hr | $2,917 |
Same method as the calculator: rated kW × the median gallons per hour per kW at each load, from 28 diesel spec sheets (standby rating, 60 Hz). Approximate: small sets of 20–30 kW run above the median, and makers differ at the large end. The generator fuel consumption chart has the spec-sheet figure for each size. Daily cost uses the example price in the calculator.
Sources: FuelGo generator fuel consumption chart (medians of 28 Cummins, Caterpillar, Generac and Kohler spec sheets, linked there) · NFPA 110 first revisions, 8.4.2 monthly exercise · EIA Gasoline and Diesel Fuel Update (U.S. on-highway diesel, $6.179, week of Oct. 12, 2026).
5 ways commercial operators cut generator fuel costs
Keep the load up
Fuel per kWh falls as load rises: about 0.089 gal/kWh at 25% load against 0.074 at full load. Long light-load runs also cause wet stacking, which is why NFPA 110 exercises run at 30% of nameplate or more.
Right-size your units
An oversized generator at low load burns more fuel per usable kWh than a correctly sized unit. Audit your actual peak demand before your next equipment decision.
Scheduled fuel delivery
Plan refills on your burn rate, not on a gauge someone reads now and then. FuelGo runs keep-full programs and monitored tanks that trigger refills on actual consumption.
Stay on top of maintenance
Clogged air filters, worn injectors and degraded fuel all push consumption up. Follow your manufacturer's service intervals and test stored fuel.
Consolidate your loads
For multi-generator sites, stagger loads to run fewer units at higher efficiency rather than many units at low load. Power management systems can automate this.
How to plan generator fuel for your project
Whether you're running generators on a construction site, at a large event, or as emergency backup for a critical facility, getting your fuel plan right upfront saves money and prevents costly downtime. Start with the calculator above to establish your baseline daily consumption, then add a 20% buffer for load spikes and inefficiencies.
For multi-week projects, set up scheduled fuel deliveries sized to your burn rate rather than calling for fuel when the gauge is low. If you want a known price for the run, FuelGo offers fixed-price diesel contracts priced off NYMEX NY Harbor ULSD futures. We deliver 20 to 4,400 gallons per drop, and transport loads up to 7,500, to construction sites, telecom towers, data centers and event venues nationwide. Dispatch runs 24/7/365, and a dispatcher replies within the hour.
Key planning checklist: Confirm your generator's rated kW and typical operating load. Calculate daily consumption using the tool above. Identify your tank capacity and set a refill trigger at 25%. Coordinate with your fuel supplier on lead times for your location. For critical operations, always have an emergency delivery number on file — ours is 800-720-4546.