Propane is stored as a liquid under pressure. Large tanks are filled to about 80% of their capacity, leaving room for the liquid to expand as it warms. That's why a 500-gallon tank only takes about 400 gallons. Small portable cylinders are sold by weight; propane weighs about 4.2 lb per gallon.
Common propane tank sizes and what a full fill costs
Costs use this week's U.S. average residential price of $2.730 per gallon (excluding tax and delivery charges). Cylinder exchanges and refills at retail locations are usually priced differently.
| Tank | Capacity (gallons) | Usable at 80% (gallons) | Approx. cost to fill |
|---|---|---|---|
| 20 lb cylinder (grill) | 4.7 | — | $13 |
| 100 lb cylinder | 23.6 | — | $64 |
| 120-gallon tank | 120.0 | 96 | $262 |
| 250-gallon tank | 250.0 | 200 | $546 |
| 320-gallon tank | 320.0 | 256 | $699 |
| 500-gallon tank | 500.0 | 400 | $1,092 |
| 1,000-gallon tank | 1,000.0 | 800 | $2,184 |
Which size do homes use?
- 120–250 gallons: a few appliances such as a range, water heater, dryer or fireplace.
- 500 gallons: the most common choice for whole-house heating in an average-size home.
- 1,000 gallons: large homes or high usage, with fewer deliveries.
See your state's price on the propane prices by state page, or estimate a delivery with the fill-up cost calculator.