Quick Answer
Tank size determines how long you can run during an extended outage. For a 22 kW generator at typical load, a 250-gallon tank (about 200 usable gallons) provides 3–4 days of runtime; a 500-gallon tank provides 6–8 days. Tanks are filled to 80% capacity as standard practice. For 7–10 kW essentials generators, a 250-gallon tank is often adequate. Cold climates and hurricane regions favor larger tanks.
Key Takeaways
- 1Run time = usable gallons ÷ consumption rate. Tanks are filled to 80% — a 500-gal tank holds ~400 usable gallons.
- 2250-gal tank: ~200 usable gallons, provides ~3–4 days for a 22 kW unit at 50% load.
- 3500-gal tank: ~400 usable gallons, provides ~6–8 days for a 22 kW unit at 50% load.
- 41,000-gal tank: provides multi-week coverage for the most demanding whole-home installations.
- 5Larger tanks in cold climates help maintain propane vaporization pressure — keep above 30–40% in winter.
- 6Leased tanks lock you into one supplier for fuel; owned tanks allow price comparison across suppliers.
Why tank size matters for generators
Unlike a natural gas generator that draws from the utility line, a propane generator is limited by how much fuel is stored on-site. How long it can run during an extended outage depends directly on two things: how fast the generator burns fuel (proportional to size and actual load) and how much propane is available in the tank.
Common propane tank sizes and their generator run-time
A 250-gallon tank holds roughly 200 gallons of usable propane — tanks are filled to 80% capacity as a standard safety practice. A 22 kW generator running at 50% load burns approximately 2.0–2.5 gallons per hour. At that rate, 200 usable gallons supports roughly 80–100 hours of operation, or about 3–4 days of continuous running.
A 500-gallon tank (about 400 usable gallons) doubles that figure to roughly 160–200 hours at the same load — approaching 7–8 days continuous. A 1,000-gallon tank provides enough propane for extended multi-week outages without a refill, though this tank size comes with higher upfront cost and requires more installation space.
Recommended tank sizes by generator capacity
For a 7–10 kW essentials-only generator: a 250-gallon tank typically provides adequate run time for most residential outage durations. For a 14–20 kW whole-home setup: a 500-gallon tank is a more comfortable fit if you want several days of run time without worrying about refills. For a 22–26 kW unit sized for full whole-home coverage including HVAC: a 500-gallon tank is a reasonable minimum; a 1,000-gallon tank provides meaningfully more cushion for extended or severe-weather outages.
Leasing vs. buying a propane tank
Many propane suppliers offer tank leases tied to a fuel delivery contract, which keeps upfront cost lower. Leased tanks require you to purchase fuel from the lessor — a consideration if other suppliers offer better pricing. Purchased tanks allow deliveries from any supplier, which provides more pricing flexibility over time.
Confirm with your installer whether the installation quote includes a tank purchase, a lease arrangement, or neither. Tank sourcing is sometimes handled separately from the generator installation itself.
Frequently asked questions
Sources
- NFPA 54 — National Fuel Gas Code — Covers gas piping and connection requirements relevant to natural gas generator installations.
- Local utility company — Utility providers set requirements for gas meter capacity and, in some cases, generator interconnection notification.
What should you do next?
See how much propane your generator actually uses per hour so you can calculate your exact run time.
Propane Consumption Guide →