Fuel use
Generator Running Cost: Natural Gas and Propane
Calculate outage fuel cost from the exact model's consumption table, expected load, runtime and current local tariff.
There is no reliable national hourly rate without the model, load and local fuel price. HomeGuide currently reports about $10–$40 per day for a typical natural-gas home generator and $30–$170 per day across whole-home systems. For a checkable result, multiply the exact model's fuel use at the chosen load by outage hours and the price in matching units.
What changes the result?
A useful calculation starts with the physical scope and the written commercial terms. These are the factors to make explicit:
- Exact model and fuel rating
- Fuel use at part and full load
- Expected simultaneous load
- Outage and exercise hours
- Local gas tariff or propane price
Use one scope for every quote
Give each business the same information and ask it to resolve the same boundaries. That makes the totals more comparable and exposes work left as an allowance or exclusion.
- Use the current model specification
- Match cubic feet or gallons to the tariff
- Calculate part-load and full-load cases
- Keep maintenance and fuel storage separate
Use fuel volume, not a national dollar multiplier
Natural-gas cost equals cubic feet per hour multiplied by hours and the local price per cubic foot or hundred cubic feet. Propane cost equals gallons per hour multiplied by hours and the delivered price per gallon. Utility bills may include fixed charges and units that need conversion, so state the tariff date and unit.
Current manufacturer consumption examples
Generac's current pages show how consumption changes by model and load. Its 14 kW example lists 189 cubic feet per hour of natural gas and 1.76 gallons per hour of propane at half load; the current 22 kW example lists 221 cubic feet per hour and 2.45 gallons per hour at half load. These are model examples, not generic generator constants.
- 14 kW at half load: 189 ft³/hr NG or 1.76 gal/hr LP
- 22 kW at half load: 221 ft³/hr NG or 2.45 gal/hr LP
Plan more than one outage scenario
Calculate an ordinary essential-load case, a higher-load case and the longest credible outage. For propane, compare required gallons with usable storage and refill access. For natural gas, have the provider or installer confirm meter, regulator and pipe capacity at full generator demand plus the building's other gas loads.
Questions people ask
How much does a whole-house generator cost to run per day?
HomeGuide reports about $10–$40 per day for typical natural-gas units and $30–$170 per day across whole-home generators, but exact model consumption and local fuel prices produce the useful answer.
Does a generator use less fuel at half load?
Generally yes, but not in direct proportion to electrical output. Use the manufacturer's part-load and full-load table for the exact model.
How do I calculate propane generator cost?
Multiply the model's gallons per hour at the expected load by outage hours and the current delivered price per gallon.
Can I assume the natural-gas service has enough capacity?
No. The meter, regulator, pipe size, pressure and other simultaneous gas loads must be checked at the generator's required full-load demand.
Method and sources
The model is a planning tool, not a quotation. These are the published sources used for this page; read the full assumptions before relying on a range. Source review: 14 September 2026.
- HomeGuide natural-gas generator cost guide
Current natural-gas daily running-cost observation and capacity factors; reviewed 14 September 2026.
- Generac 14 kW product page
Current model-specific part- and full-load fuel data; reviewed 14 September 2026.
- Generac 22 kW product page
Current model-specific part- and full-load fuel data; reviewed 14 September 2026.