What Size Propane Tank for a House Generator?

Why Propane Tank Size Matters More Than You Think

Propane is one of the best fuels for generators — it never goes bad, burns cleaner than gasoline, and can be stored indefinitely. But propane tank sizing is often misunderstood. A generator's runtime depends on both the generator's load and the tank's capacity, measured in gallons or pounds.

For portable generators, LP conversion kits allow propane use with standard 20 lb grill tanks (about 4.7 gallons). A 3,500W generator running at 50% load burns about 0.8-1.0 gallons of propane per hour, giving you about 4-5 hours per 20 lb tank. For multi-day outages, you'd need multiple tanks or a larger 100 lb tank (about 23 gallons).

For whole-house standby generators, the propane tank needs to be permanently installed. A 14kW Generac at full load burns about 1.6 gallons of propane per hour. Over a 3-day outage, that's 115 gallons — requiring a 250-gallon minimum tank. A 500-gallon tank provides about 7-8 days of runtime at 50% load, which is the recommended safety margin for extended outages.

Top picks for this size

Propane Tank Sizing Guide by Generator Type

• Portable 3,500W (Champion, WEN): 20 lb tank (~4.7 gal) gives 4-5 hours at 50% load. Stock 2-3 tanks for 24-hour coverage. Upgrade to 100 lb tank (~23 gal) for multi-day outages.
• Portable 7,500W (Westinghouse, Generac GP): 100 lb tank (~23 gal) gives 10-14 hours at 50% load. Consider a 420 lb tank (~100 gal) for extended backup.
• Standby 14kW (Generac 14kW): 250 gallon minimum tank — 3-4 days of runtime at 50% load. 500 gallon recommended for areas with frequent or long outages.
• Standby 22kW (Generac 22kW): 500 gallon tank — 3-5 days at 50% load due to higher consumption (1.8-2.0 gal/hr). 1,000 gallon for coastal/hurricane areas.

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