Generator Running Cost Calculator
Once you know the required running and starting watts, use the generator manufacturer's fuel-consumption data at your expected load to estimate outage fuel cost.
Quick answerAt the default 0.75 gal/hour, $3.50/gallon and 8 hours/day, fuel costs $2.63 per hour, $21 per day or $147 for seven days. The result is only as accurate as the consumption input—use your exact model, fuel and expected load rather than a generic generator-size estimate.
Change any number below — your result updates instantly, no button to click.
Your details
Results
Measure or improve the real-world result
These tools are relevant to the numbers above; you do not need them to use the calculator.
As an Amazon Associate we earn from qualifying purchases. We may earn a commission from links on this page, at no extra cost to you.
How it works
Cost per hour = fuel consumption (gal/hr) × fuel price. Cost per day = cost per hour × hours run per day. Cost per week = cost per day × 7 — useful for planning a multi-day outage. Consumption rate varies with generator load: a generator running at 25% load burns noticeably less fuel per hour than at 100% load, so use the rate closest to your actual usage, not the maximum-load spec.
Fuel-cost examples at $3.50 per gallon
Eight operating hours per day, shown to illustrate how model-specific consumption changes the budget.
| Consumption | Cost / hour | Cost / 8-hour day | Cost / 7 days |
|---|---|---|---|
| 0.25 gal/h | $0.88 | $7 | $49 |
| 0.50 gal/h | $1.75 | $14 | $98 |
| 0.75 gal/h | $2.63 | $21 | $147 |
| 1.00 gal/h | $3.50 | $28 | $196 |
These are arithmetic examples, not fuel-consumption claims for a particular generator.
Worked example with the default values
Hourly cost = 0.75 gal/hour × $3.50/gallon = $2.625, displayed as $2.63. Daily cost at eight hours = $2.625 × 8 = $21. A seven-day outage at that schedule costs $21 × 7 = $147.
This is fuel purchase cost only. Oil, filters, maintenance, transport, storage containers, taxes and depreciation are outside the formula.
Derive gallons per hour from a runtime specification
If a gasoline specification lists tank capacity and runtime, average consumption = tank gallons ÷ runtime hours. Honda lists a 6.2-gallon tank and 9.8 hours at half load for the EB6500, which gives about 0.63 gal/hour. Its 6.4-hour rated-load runtime gives about 0.97 gal/hour. Those are derived averages for that one model and test load—not universal generator rates.
Use the rating for your actual fuel. Dual-fuel models can have different output and runtime on gasoline and propane, and a runtime statement does not describe every changing load during a real outage.
Load changes both fuel use and cost per delivered kWh
A generator generally burns more fuel per hour as electrical load rises, but very light loading may also be inefficient per kWh delivered. Build a load list, separate running watts from starting surges, and use the manufacturer curve nearest the expected sustained load.
Avoid treating the generator's maximum wattage as continuous consumption. The electrical load tells you where to read the fuel curve; it does not convert directly to gallons without model-specific efficiency data.
Generator safety is not part of the cost calculation
Never operate a portable generator inside a home, garage, basement, shed or other enclosed or partly enclosed space. CPSC warns that carbon monoxide can kill in minutes and advises operating portable generators outside at least 20 feet from the house, with exhaust directed away. Follow the manual and current local guidance.
Keep the generator dry, let it cool before refueling, store fuel in approved containers, and use a qualified electrician for home wiring or transfer equipment. A lower fuel-cost result never makes an unsafe placement or connection acceptable.
Sources used for assumptions: Honda Power Equipment — EB6500 specifications and runtime; U.S. Consumer Product Safety Commission — Portable generator safety; OSHA — Using Portable Generators Safely.
Frequently asked questions
How much fuel does a generator use per hour?
It varies by exact model, fuel and load. Use a manufacturer consumption curve or divide tank capacity by stated runtime at the closest tested load.
Can I calculate propane cost with this page?
Yes if you enter propane consumption and price in the same volume unit. If the manual gives pounds per hour, convert both consumption and price to pounds rather than mixing pounds and gallons.
Which generator fuel is cheapest?
There is no reliable universal order. Compare model-specific consumption on each fuel with current local delivered prices and any fixed connection or storage costs.
Should I use half-load or full-load consumption?
Use the curve point nearest your expected sustained load. If demand varies, calculate a lower- and higher-load scenario or use a weighted average from planned operating periods.
Should I run a generator all day during an outage?
Model the schedule required for essential loads and follow appliance, food-safety and medical needs. Fewer hours reduce fuel use, but never compromise safety-critical equipment.
Does this include generator maintenance?
No. It calculates fuel only. Add oil, filters, scheduled service, fuel storage and transport, and eventual replacement for a broader outage budget.
How far should a portable generator be from the house?
CPSC advises operating it outside at least 20 feet from the house, with exhaust directed away. Never use it in an enclosed or partly enclosed space; follow the manual and current local rules.
Related calculators
Generator Size Calculator
A generator has two limits: continuous running output and brief starting output. Add the w…
BatteryBattery Backup Runtime Calculator
Whether sizing a home backup battery or a portable power station, this calculator estimate…
SolarHome Battery Payback Calculator
A home battery saves money by storing cheap (or solar) electricity and using it when power…