Generator Running Cost Calculator
Knowing how much fuel a generator uses is only part of the picture. The price of that fuel, the number of hours you run the generator, and routine upkeep can all affect the total. The Generator Running Cost Calculator brings those inputs together to estimate what a period of generator operation may cost.
Whether you are preparing for an outage, planning a camping trip, or comparing equipment for a worksite, the estimate gives you a useful starting point. Enter an average fuel consumption rate that reflects your expected load, your planned running time, and the price you expect to pay for fuel. You can also include an hourly maintenance allowance.
What the Generator Running Cost Calculator does
This generator running cost calculator estimates the combined fuel cost and maintenance allowance for a specified number of operating hours. Its result, labeled Estimated Cost, is displayed in dollars to two decimal places.
The calculation assumes the generator consumes fuel at the average rate you enter for the entire running period. It also assumes the fuel price and maintenance allowance remain constant. The default values are illustrative assumptions, so replace them with figures that fit your generator and situation.
The estimate covers operating costs represented by the inputs. It does not include the generator’s purchase price, financing, or repairs beyond the maintenance allowance. Other fixed costs are also excluded. Treat the result as a planning estimate rather than a guaranteed bill.
How to use the Generator Running Cost Calculator
Gather an estimated fuel consumption rate for the load you expect to run, the operating time, and a fuel price. Then enter the following values:
- Fuel consumption (gallons per hour): Enter the average amount of fuel the generator is expected to use in one hour, measured in US gallons. Use a rate that reflects your expected electrical load whenever possible.
- Running time (hours): Enter the total number of hours you expect to operate the generator. This can represent a single session or the combined hours across a longer period.
- Fuel price ($ per gallon): Enter the price you expect to pay for one US gallon of the fuel your generator uses.
- Maintenance allowance ($ per hour): Enter an average hourly amount to budget for maintenance. This input is optional; enter 0 if you want to exclude it.
Read the Estimated Cost as the projected total for the running time you entered. To compare scenarios, change an input and review how the estimate changes. For example, you can compare a shorter outage with a longer one, or use different fuel consumption assumptions for different loads.
Check the units before entering a figure. If your generator’s documentation lists consumption in another unit, convert it to US gallons per hour first. A fuel consumption figure for a full tank or a complete run is not automatically an hourly rate; divide the fuel used by the number of operating hours to find an average gallons-per-hour figure for that period.
How the Generator Running Cost Calculator formula works
The calculator first estimates the fuel cost for one hour. It adds the hourly maintenance allowance, then multiplies the combined hourly amount by the number of running hours:
Estimated Cost = Running time × [(Fuel consumption × Fuel price) + Maintenance allowance]
Fuel consumption is measured in US gallons per hour, fuel price is in dollars per gallon, and the maintenance allowance is in dollars per hour. Multiplying gallons per hour by dollars per gallon gives a fuel cost per hour. Adding the maintenance allowance gives the estimated operating cost per hour.
Worked example using the default inputs
Suppose you use the calculator’s illustrative default assumptions: a generator consumes 0.75 gallons per hour, runs for 8 hours, and uses fuel priced at $3.50 per gallon. You also include a $0.25 per hour maintenance allowance.
- Hourly fuel cost: 0.75 × $3.50 = $2.625
- Fuel cost for 8 hours: $2.625 × 8 = $21.00
- Maintenance allowance for 8 hours: $0.25 × 8 = $2.00
- Estimated Cost: $21.00 + $2.00 = $23.00
The $3.50 fuel price and the other default figures are assumptions for this example, not claims about current prices or the performance of a particular generator. Your actual cost will depend on your equipment, load, fuel price, and maintenance expenses.
Use cases for the Generator Running Cost Calculator
Home backup power: Estimate the fuel and maintenance budget for a potential outage. Try several running-time assumptions to see how the projected cost changes if power is out longer than expected. If you plan to run the generator only during certain hours, enter those operating hours rather than the full length of the outage.
Camping and recreational trips: Estimate the cost of running a generator during the hours you expect to use appliances or charge equipment. Base the consumption rate on the anticipated load and check the operating rules at your destination when planning your schedule.
Worksite planning: Use an estimated daily or weekly running time to budget for portable power. If equipment use varies throughout the day, consider estimating separate periods with appropriate average consumption rates and adding the results.
Comparing operating scenarios: Estimate the effect of different fuel consumption rates or fuel prices. Keep the running time and other assumptions consistent when comparing options, and remember that operating cost is only one part of the overall cost of owning or renting a generator.
Maintenance budgeting: Include an hourly allowance to recognize that routine upkeep has a cost. This can help you plan beyond fuel alone, although the allowance remains an estimate and may not match the timing or amount of actual maintenance expenses.
Other factors to consider when calculating Estimated Cost
Electrical load: A generator’s fuel consumption can change as the amount of electricity it supplies changes. An average rate based on your expected load is generally more useful for this calculation than a rate taken from a different operating condition. If the load varies significantly, one average rate may not capture every part of the run.
Operating conditions and efficiency: Generator specifications, equipment condition, and operating conditions can affect actual fuel use. Manufacturer information can provide a starting point, but the rate you enter remains an assumption unless it reflects your own measured use under comparable conditions.
Fuel price changes: The formula applies one price to all fuel consumed during the entered period. If you expect to buy fuel at different prices, estimate each period separately and add the results. Make sure the price and consumption figures use the same US-gallon unit.
Maintenance allowance: The hourly amount is a budget estimate supplied by you. It can represent an average share of routine operating maintenance, but actual expenses may occur at irregular intervals. Set the allowance to zero for a fuel-only estimate, or choose an amount based on the costs you want to include.
Costs outside the calculation: Purchase costs, financing, and repairs beyond the allowance are excluded. Depending on your situation, delivery, storage, installation, or other expenses may also matter. Account for applicable costs separately when building a broader generator budget.
Generator Running Cost Calculator FAQ
How much does it cost to run a generator for eight hours?
It depends on fuel consumption, fuel price, and any maintenance allowance. With the calculator’s illustrative defaults of 0.75 gallons per hour, $3.50 per gallon, and $0.25 per hour for maintenance, eight hours produces an Estimated Cost of $23.00. Enter your own figures for a more relevant estimate.
How do I find my generator’s fuel consumption per hour?
Check the generator’s documentation for a consumption rate at a load similar to the one you expect. If you have a measured amount of fuel used over a known number of hours, divide the US gallons used by those hours to find the average rate for that period. Actual consumption can change when the load or operating conditions change.
Can I calculate fuel cost without maintenance?
Yes. Enter 0 for the maintenance allowance. The result will then equal fuel consumption per hour multiplied by running time and fuel price.
Does the calculator account for changes in generator load?
The formula uses one average fuel consumption rate for the full running time. It does not automatically adjust the rate as the load changes. If you have reasonable rates for distinct operating periods, calculate each period separately and add the estimates.
Does Estimated Cost include the price of the generator?
No. Estimated Cost covers fuel and the hourly maintenance allowance you enter. It excludes the generator’s purchase price, financing, repairs beyond that allowance, and other fixed costs.