Propane tank sizes, explained
A 500-gallon tank holds 400 gallons when full. At this week’s U.S. average of $2.73 a gallon, filling it from 20% costs about $819.
Prices: EIA weekly residential survey, week of October 26, 2026.
Sizes, capacity and cost to fill
| Tank | Typical use | Holds at 80% | Fill from 20% | Cost at $2.73 |
|---|---|---|---|---|
| 120 gallons Often vertical, near the house | Cooking, a fireplace or a water heater | 96 gal | 72 gal | $197 |
| 250 gallons Horizontal, above ground | Water heater plus cooking, or heat for a small, mild-climate home | 200 gal | 150 gal | $410 |
| 500 gallons The most common home heating tank | Whole-house heat for a typical home | 400 gal | 300 gal | $819 |
| 1000 gallons Often buried | Large homes, cold climates, or heat plus a pool or generator | 800 gal | 600 gal | $1,638 |
Grill cylinder (pounds, not gallons: a 20 lb cylinder holds about 4.7 gallons).
How long does a full 500-gallon tank last in January?
- Minnesota44 days213 gal in a normal January
- Pennsylvania64 days145 gal in a normal January
- North Carolina96 days97 gal in a normal January
- Texas147 days63 gal in a normal January
For heat only, 2,000 sq ft average house, a 300-gallon delivery (20% to 80%). Our estimate from NOAA normal degree days; your use depends on the house and thermostat.
Why only 80%?
Liquid propane expands as it warms: roughly 1.5% for every 10°F. The 80% limit leaves room so a tank filled on a cold morning does not over-pressurize on a warm afternoon. Every tank gauge reads percent of the full water capacity, so “80%” on the dial is full.
Owning versus leasing
Leased tanks usually tie you to the dealer that owns them. Owning the tank lets you shop for price each fill, which matters when dealers in one state can differ by more than a dollar a gallon. Check the lease terms before the heating season.