How long a 120 gallon propane tank lasts, by appliance
This is a small bulk tank for a workshop, cabin or a few appliances. It holds about 96 gallons of propane, which is 8,784,000 BTU. Runtimes are for the appliance running continuously, at full power and at 70% of its rating, with no refills.
| Appliance | BTU/hr | At full power | At 70% power |
|---|---|---|---|
| Gas grill, 2-burner | 24,000 | 366 h | 523 h |
| Gas grill, 3-burner | 36,000 | 244 h | 349 h |
| Patio heater | 40,000 | 220 h | 314 h |
| RV furnace | 30,000 | 293 h | 418 h |
| Tank water heater | 40,000 | 220 h | 314 h |
| Fire pit | 50,000 | 176 h | 251 h |
| Gas range (everything on, max) | 65,000 | 135 h | 193 h |
| Whole-house furnace | 80,000 | 110 h | 157 h |
| Tankless water heater | 150,000 | 58.6 h | 83.7 h |
Tips and safety
Bulk tanks are filled to 80% of capacity, and are best arranged on a regular delivery. Order a refill before the gauge reads 20 to 30%, and keep the tank clear of snow and vegetation. Use the propane runtime calculator for your own appliance, and see the propane tank guide for the formula and safety checklist.
Equivalents and practical notes
This tank holds the same propane as about 20 standard 20 lb cylinders, at 407 lb of propane.
Bulk tanks are filled by a delivery truck to 80% of capacity, and usually need a safe distance from the house and property lines (often 10 ft or more, set by local code and the tank size). Many suppliers offer automatic delivery, or a gauge reading you can check yourself.
Want to change anything else? The calculator above is the full Propane Tank Runtime Calculator: edit any number and the results update instantly.
Tools & materials for this project
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Frequently asked questions
How long does a 120 gallon propane tank last on a grill?
About 244 h of cooking at full power on a 3-burner grill (36,000 BTU/hr), or 349 h at a more typical 70% of full power. A 2-burner grill (24,000 BTU/hr) gets 366 h at full power.
How many gallons of propane are in a 120 gallon tank?
About 96 gallons usable, because bulk tanks are filled to 80% of their water capacity. That is 8,784,000 BTU of energy.
How long will a 120 gallon propane tank run a furnace?
A whole-house furnace rated at 80,000 BTU/hr burning non-stop uses a 120 gallon tank in about 110 h (4.6 days). A furnace cycles on and off, so a tank lasts longer in practice. Smaller or more efficient homes use less.
Related sizes and guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.