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Calcimator

Emergency Generator Fuel Calculator

Calculate fuel storage needs for emergency generator runtime based on generator size, load, fuel type, and duration.

Inputs

%
%

Results

Total fuel needed (gal)

46.6

Fuel consumption (gal/hr)0.56
5-gallon cans needed10
Runtime per can (hrs)8.9
Actual output (kW)3.8
Est. fuel cost ($)$163.01
Safety reserve (gal)6.1
Fuel shelf life (months)6
How to Use This Calculator
  1. Enter Generator Size (kW) and Average Load (%) expected during operation.
  2. Set Target Runtime (hours) for the emergency event.
  3. Select Fuel Type (diesel, gasoline, or natural gas).
  4. Enter Safety Margin % to ensure adequate reserve.
  5. Review Total Fuel Needed (gallons) and Consumption Rate (GPH) to plan storage and resupply logistics.

How the result changes with Generator size (kW)

Generator size (kW)Total fuel needed (gal)
1168.3
36223.6
65403.7
90558.9

What each input means

Generator size (kW)
Rated output of the generator in kilowatts (typical home: 5-22 kW).
Avg load (%)
Average load as percentage of rated capacity. 50% is typical for intermittent use.
Target runtime (hours)
Total hours of generator operation needed (72 hrs = 3-day outage).
Fuel type (0-2)
0 = Gasoline, 1 = Diesel, 2 = Propane (LP).
Safety margin (%)
Extra fuel reserve beyond calculated need.

What each result means

Total fuel needed (gal)
Total gallons of fuel to store including safety margin.
Fuel consumption (gal/hr)
Gallons per hour at specified load.
5-gallon cans needed
Standard fuel cans to purchase and store.
Runtime per can (hrs)
Hours of runtime from a single 5-gallon can.
Actual output (kW)
Actual power output at your specified load percentage.
Est. fuel cost ($)
Approximate fuel cost based on average prices.
Safety reserve (gal)
Extra fuel included as safety buffer.
Fuel shelf life (months)
Typical shelf life: gasoline ~6 mo, diesel ~12 mo, propane indefinite.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Generator size (kW) = 7.5, Avg load (%) = 50, Target runtime (hours) = 72, Fuel type (0-2) = 0 = 5 input(s) provided
  2. Calculate Total fuel needed
    Total fuel needed = baseFuelGallons + safetyReserveGallons
    46.6 = 46.6
  3. Calculate Fuel consumption
    Fuel consumption = generatorKW * baseRate * loadFactor
    0.56 = 0.56
  4. Calculate 5-gallon cans needed
    5-gallon cans needed
    10 = 10

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