Generator Fuel Cost Calculator
Calculate how much fuel your generator consumes and what it costs to run — per hour, per day, and compared to grid electricity.
Generator vs. Grid Electricity
Generator power is — more expensive than grid electricity per kWh.
Fuel Use by Generator Size (50% load, gasoline at $3.50/gal)
| Generator Size | Gal/Hour | Cost/Hour | Cost/Day (8 hrs) |
|---|---|---|---|
| 2,000W | 0.10 | $0.35 | $3 |
| 3,500W | 0.18 | $0.61 | $5 |
| 5,000W | 0.25 | $0.88 | $7 |
| 7,500W | 0.38 | $1.31 | $11 |
| 10,000W | 0.50 | $1.75 | $14 |
| 15,000W | 0.75 | $2.63 | $21 |
| 20,000W | 1.00 | $3.50 | $28 |
Frequently Asked Questions
How much fuel does a generator use per hour?
A portable 5,000W generator at 50% load uses roughly 0.5–0.7 gallons of gasoline per hour. At 100% load, it uses 0.8–1.2 gallons/hour. Rule of thumb: portable generators use about 0.1 gallons/kWh at 50% load. Larger standby generators (10,000–20,000W) use 1–2 gallons/hour at 50% load. Propane generators use 2–3× the volume but propane is denser in BTUs.
How much does it cost to run a generator per day?
A 5,000W portable generator running 8 hours/day at 50% load uses 4–5.6 gallons of gasoline, costing $14–$20/day at $3.50/gallon. A whole-home standby generator (20,000W) running continuously on natural gas costs $5–$15/day. Diesel generators are 25–30% more fuel-efficient than gasoline but diesel fuel costs more per gallon.
Generator vs. grid electricity — which is cheaper?
Grid electricity almost always wins on cost. Running a generator produces electricity at $0.40–$1.00+/kWh after fuel costs, vs. $0.10–$0.20/kWh from the grid. Generators make financial sense only during outages when grid power is unavailable. The break-even for a whole-home standby generator (installed cost $5,000–$12,000) requires frequent, extended outages that are rare except in hurricane-prone areas.
What size generator do I need?
Calculate your essential loads: refrigerator (600W), window AC (1,200W), lights (200W), phone/laptop charging (100W), sump pump (750W), TV (150W) = ~3,000W for essentials. Add 25% for motor starting surges: 3,750W minimum. A 5,000W generator provides comfortable headroom. For whole-home coverage including central AC, you need 10,000–20,000W.
Can I run my generator on propane or natural gas?
Dual-fuel or tri-fuel generators can run on gasoline, propane, and natural gas. Propane produces about 25% less power per gallon-equivalent than gasoline but stores indefinitely (gasoline degrades in 3–6 months). Natural gas whole-home standby generators never run out of fuel during emergencies — the biggest advantage. Propane portable generators need large tanks for extended use.