Transformers & motors
Generator Fuel Consumption & Runtime Calculator
Generator fuel use comes only from manufacturer or measured data points entered by the user. The calculator interpolates between surrounding points and does not extrapolate outside their range. The method follows the electrical relationships and NIST unit references documented on the Electrical Formulas and Sources pages.
Calculate generator fuel consumption, runtime, outage fuel, and cost from explicit manufacturer or measured fuel-use data.
Calculated result
Generator fuel plan
Calculating…
Calculated locally in your browser
Planning math only. Verify equipment specifications and installation requirements separately.
Equipment planning
Compatible options to compare
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Calculate above to generate a parts requirement.
Cable, fuse, breaker, disconnect, mounting, grounding, and code requirements need separate equipment and installation review.
What this calculator returns
Enter the exact model's manual data or measurements at comparable conditions. A result is unavailable outside the entered range because extrapolation is deliberately blocked.
Formula and variables
The calculation runs entirely in your browser. Static formulas, definitions, examples, and tables remain readable without JavaScript.
Load % = electrical load kW ÷ rated real kW × 100. Fuel/hour is the exact entered value or linear interpolation between the nearest entered points. Runtime/tank = tank ÷ fuel/hour; cost = fuel × price.
- Prated
- Entered generator real-power rating, or kVA rating converted with the entered power factor.
- L
- Current electrical load expressed as a percentage of rated real power.
- F
- Fuel use per hour from an exact entered point or interpolation between surrounding points.
- Vtank
- Entered usable tank volume or total fuel available in gallons or liters.
- t
- Runtime in hours used for tank, daily, and outage totals.
Rated kVA is converted to kW with the entered power factor. Fuel units remain gallons or liters throughout; the calculator does not convert fuel energy content.
Worked example
| Input | Value |
|---|---|
| Generator rating unit | kW |
| Generator rated output | 10 kW / kVA |
| Current load entered as | Load percentage |
| Current load | 50 % / kW |
As input-format arithmetic only, fuel points of 0.6 gal/h at 25% and 1.4 gal/h at 75% would interpolate to 1.0 gal/h at 50%. An 8-gallon tank would then represent 8 hours before reserve or inaccessible fuel. Do not use these example numbers as generator specifications.
Reference table
| Entered load position | Calculator behavior | Fuel basis |
|---|---|---|
| Matches a data point | Uses that value directly | Exact entered value |
| Between two data points | Linear interpolation | Two surrounding entered values |
| Below or above the data range | Stops with a validation message | No extrapolation |
Frequently asked questions
Why must I enter fuel consumption?
Fuel use varies by generator design, fuel, speed, load, and conditions. Manufacturer data or measured values avoid inventing a universal curve.
What happens outside my entered fuel-data range?
The calculator stops and asks for another data point. It never silently extrapolates.
Can I use liters instead of gallons?
Yes. Choose liters and enter both tank size, hourly consumption, and price in liters; no cross-unit conversion is needed.
Assumptions and limitations
- No universal gasoline, diesel, propane, or natural-gas curve is assumed.
- Fuel-use inputs are blank by default so an example cannot be mistaken for a real generator specification.
- Altitude, temperature, fuel quality, maintenance, transient load, reserve fuel, and inaccessible tank volume are not predicted.
- No generator sizing, transfer equipment, ventilation, storage, electrical installation, or code-compliance determination.
Method and sources
Review the electrical formulas, calculation methodology, and standards status for the references most relevant to this calculation. The broader technical sources index records source scope and provenance. Content release .