Also in: Disaster Response and Recovery
Generator Fleet Fuel Resupply
After a hurricane a county's temporary power is dozens of generators of different sizes at hospitals, lift stations.
Example
You enter
- Size 1: number of units 4
- Size 1: rating (kW) 60
- Size 1: tank (gal) 100
- Size 1: actual burn if known (gph, 0 = USACE rule) 0
- Size 2: number of units (0 if unused) 6
- Size 2: rating (kW) 150
- Size 2: tank (gal) 300
- Size 2: actual burn if known (gph, 0 = USACE rule) 0
- Size 3: number of units (0 if unused) 2
- Size 3: rating (kW) 300
- Size 3: tank (gal) 500
- Size 3: actual burn if known (gph, 0 = USACE rule) 0
- Usable fraction of each tank 0.9
- Fuel truck deliverable volume (gal) 2400
You get
- Fleet (kW) 1740
- Fleet fuel per day 2923.2
- USACE rule at 70% load, for comparison 2,046 gal/day, 1 trips
- Truck trips per day 2
- Trips per day 70 1
- Size1 interval hours 21.4286
- Size2 interval hours 25.7143
- Size3 interval hours 21.4286
- Route must return within 21.4286
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
ScopeShelters, and cell sites, and they all run dry on their own schedules. This calculator totals a fleet of up to three generator sizes: the burn per unit by the USACE rule of thumb recorded in the EPA Power Resilience Guide -- 0.07 gallons an hour per kW of rating, printed with no load basis and close to (sometimes under) a diesel's full-load burn -- or the unit's own burn where known; the fleet's gallons a day; the tank-truck trips; and each size's refuel interval from its tank and usable fraction. The interval that matters is the SHORTEST, because the route must come back around before the first unit runs dry. Four 60 kW units on 100 gal tanks, six 150 kW units on 300 gal tanks, and two 300 kW units on 500 gal tanks, 90% usable, on a 2,400 gal truck: 1,740 kW burns 2,923 gallons a day, two trips, but the 60 kW and 300 kW units both run dry every 21.4 hours, so a once-a-day route misses both. At the EPA guide's 70% comparison the fleet burns about 2,046 gallons, one truckload. It does not route trucks, account for travel time, access, or curfews, or address fuel storage, spill containment, or fuel quality, and it does not size generators. The EPA guide, the fuel supplier, the manufacturers' data, and the incident's logistics section govern.
Formula or tableburn per unit = 0.07 gal/h x kW rating (USACE rule) or the unit's entered gph; fleet gallons per day = sum of count x burn x 24 h; trips per day = ceil(daily gallons / truck deliverable gallons); refuel interval = tank gallons x usable fraction / burn; the shortest interval sets the route cycle; comparison at 70% load = 0.7 x the rule-of-thumb daily total.
Source and editionEPA, Power Resilience Guide for Water and Wastewater Utilities (2023), Section 4, recording the U.S. Army Corps of Engineers rule of thumb of 0.07 gallons per hour per kW (printed with no load basis), and one utility manager's practice of stocking for 70% load, named as the default basis; each unit's published fuel curve named as governing where known.
Free accessA federal planning figure and arithmetic on the user's own fleet, tank, and truck sizes; nothing proprietary is reproduced.
What governsEstimate. AHJ and licensed professional govern.
API field namessize1_count, size1_kw, size1_tank_gal, size1_burn_gph, size2_count, size2_kw, size2_tank_gal, size2_burn_gph, size3_count, size3_kw, size3_tank_gal, size3_burn_gph, usable_fraction, truck_gal, fleet_kw, fleet_fuel_gal_per_day, fleet_fuel_70_gal_per_day, trips_per_day, trips_per_day_70, size1_interval_hours, size2_interval_hours, size3_interval_hours, shortest_interval_hours
- 0.07 gph per kW the USACE rule of thumb per kW of rating, printed with no load basis; it sits near a diesel's full-load burn, so it is conservative for lightly loaded unitsEPA Power Resilience Guide (2023), Section 4
- Shortest interval sets the route every unit must be reached before the first one runs dryproject method
- 70% comparison the rule scaled linearly to 70% load; a real fuel curve is not linear and burns more than this at part load (Cummins DQDAC: 16.6 gal/h at 70% against 14.7 by scaling)one utility manager's practice, quoted in the EPA Power Resilience Guide (2023)