Generator fuel cost comparison
What does a day of backup power cost on each fuel? Pick a generator class and enter your local fuel prices; the calculator applies the class's median published half-load consumption from the models in the BackupAtlas database. Where a class has no published figure for a fuel, the row is omitted rather than guessed.
Estimated cost at ~50% load
| Fuel | Consumption (half load) | Cost per day | Cost per week |
|---|
Assumptions (the honest part)
- Consumption figures are the median of published spec-sheet values for the models in each class: gasoline burn is tank size ÷ rated half-load runtime, propane and natural gas are the manufacturers' half-load consumption figures. Individual models vary — each model page shows its own numbers.
- Everything assumes roughly 50% load. Load matters, but not linearly: at 25% load a generator burns about 60–65% of its half-load fuel, not half — engine overhead dominates at light loads. A lightly loaded generator is cheaper per hour but more expensive per kilowatt-hour.
- Natural gas is converted at 97 ft³ ≈ 1 therm. Default prices are national average residential figures ($3.2/gal gasoline, $2.7/gal propane, $1.45/therm) — override them with your local rates.
- This is fuel cost only: no maintenance, oil, or installation. For the standby-specific math, see what a natural-gas standby costs to run.