Quick Answer
Propane consumption depends on generator size and how hard it's working — not just the nameplate kW rating. At 50% load (a reasonable default for typical home use): a 7 kW generator burns 0.6–1.0 gal/hr; a 14 kW burns 1.3–1.9 gal/hr; a 22 kW burns 2.0–2.8 gal/hr; a 26 kW burns 2.4–3.5 gal/hr. Running central air conditioning pushes load and consumption toward the higher end.
Key Takeaways
- 1Consumption tracks actual load, not nameplate kW — a 22 kW generator at 25% load uses far less than one at full load.
- 2At 50% load (typical residential): 7 kW ≈ 0.6–1.0 gal/hr; 14 kW ≈ 1.3–1.9 gal/hr; 22 kW ≈ 2.0–2.8 gal/hr.
- 3Running central air conditioning is the single biggest load driver — expect higher consumption in summer outages.
- 4To estimate run time: divide usable tank gallons by expected hourly consumption rate.
- 5Before storm season, fill the tank to near 100% rather than letting it sit at 50%.
- 6Contact your propane supplier early in a multi-day outage — delivery wait times spike after major weather events.
Why the kW rating doesn't tell the whole story
A 22 kW generator doesn't always burn propane at its maximum rated rate — it burns fuel in proportion to the actual electrical load being drawn from it. A generator running a refrigerator, some lights, and a sump pump might be at 20–30% of rated capacity; the same generator running central air and the kitchen simultaneously might be at 60–80%. Actual consumption tracks load, not nameplate capacity — which is why correct sizing affects operating cost as well as coverage.
Typical propane consumption by generator size
At 50% load — a reasonable estimate for typical residential use — approximate consumption rates are: 7 kW generator: 0.6–1.0 gallons per hour. 14 kW: 1.3–1.9 gallons per hour. 20 kW: 1.8–2.5 gallons per hour. 22 kW: 2.0–2.8 gallons per hour. 26 kW: 2.4–3.5 gallons per hour.
At 25% load, consumption drops by roughly 30–40% from the 50% figures. At full load (100%), consumption rises to roughly 1.5–2x the 50% rate. Running central air conditioning in summer heat is the single biggest load driver in most homes.
| Generator Size | 25% Load (gal/hr) | 50% Load (gal/hr) | 75–100% Load (gal/hr) | Est. Days on 500-gal Tank (50% load) |
|---|---|---|---|---|
| 7 kW | 0.4–0.6 | 0.6–1.0 | 1.0–1.5 | 17–28 days |
| 14 kW | 0.8–1.2 | 1.3–1.9 | 2.0–2.8 | 9–13 days |
| 20 kW | 1.1–1.6 | 1.8–2.5 | 2.8–3.8 | 7–9 days |
| 22 kW | 1.2–1.8 | 2.0–2.8 | 3.0–4.2 | 6–8 days |
| 26 kW | 1.5–2.2 | 2.4–3.5 | 3.8–5.0 | 5–7 days |
Run-time calculations
To estimate run time, divide the usable gallons in your tank by your expected consumption rate. A 500-gallon tank holds about 400 usable gallons at standard 80% fill. A 22 kW generator at 50% load consuming about 2.5 gallons per hour would run approximately 160 hours — about 6–7 days — on a full 500-gallon tank.
If you plan to run central air through a summer outage, use 70–75% load in your estimate. If running essentials only, 30–40% load is a reasonable lower bound.
How to use consumption estimates for outage planning
Before a storm season, confirm your tank is at or near 100% fill rather than 50%. During a multi-day outage, reducing unnecessary loads — turning off electric water heaters, limiting electric oven use — extends run time meaningfully. If the outage extends beyond 3–4 days, contacting your propane supplier early to schedule a delivery is advisable. Wait times for propane delivery can extend significantly after major storms when regional demand spikes — which is a strong argument for sizing the tank generously up front.
Frequently asked questions
Sources
- NFPA 54 — National Fuel Gas Code — Covers gas piping and connection requirements relevant to natural gas generator installations.
- U.S. Department of Energy — Building America Solution Center — Publishes consumer and contractor guidance on backup power options and home energy resilience.
What should you do next?
Use your consumption rate to determine what size propane tank will last through your typical outage scenario.
Propane Tank Sizing Guide →