Propane Usage Calculator
Estimate propane runtime based on the amount of propane available and the hourly consumption rate of your appliance or system.
Storing propane for a generator? Pair this with the Fuel Storage Calculator or the Generator Runtime Calculator for your full backup fuel plan.
Calculate propane runtime
Enter how much propane you have and how much your appliance uses per hour.
40.0 hours
100 lb at 2.5 lb/hr
Tips for success
- Energy content: 1 gallon of propane contains ~91,500 BTU of energy.
- Standard tank sizes: 20 lb (~4.6 gal), 30 lb (~7 gal), 100 lb (~24 gal), plus bulk tanks (250–1,000 gal).
- Cold weather: reduces vapor pressure. 20-lb cylinders can't deliver enough BTU for high-draw appliances below ~20°F.
- Shelf life: propane stores indefinitely in sealed cylinders, but regulators and hoses should be inspected annually.
Practical note
Appliance BTU ratings are maximum input under full load. Most real usage is at partial load (a furnace cycles, a grill runs on medium), so actual propane consumption is typically 50–70% of the rated worst case. Track a few burn cycles with a scale or gauge before committing to a storage strategy, then add a 20–30% buffer for cold snaps and extended outages.
How long does propane last?
Runtime depends on the appliance's BTU draw and how much propane you have. The table below shows continuous burn time for common appliances on a full 20-lb BBQ cylinder and a 100-lb cylinder, using propane's energy content of about 21,600 BTU per pound. Real-world times run longer because most appliances cycle on and off rather than burning flat out.
| Appliance | Typical draw | 20-lb tank | 100-lb tank |
|---|---|---|---|
| Lantern or single-burner camp stove | ~8,000 BTU/hr | ~54 hr | ~270 hr |
| Patio grill, medium heat | ~15,000 BTU/hr | ~29 hr | ~144 hr |
| Portable radiant heater, high | ~18,000 BTU/hr | ~24 hr | ~120 hr |
| Large grill or burner, full | ~30,000 BTU/hr | ~14 hr | ~72 hr |
| RV furnace | ~35,000 BTU/hr | ~12 hr | ~62 hr |
| Portable generator, ~3.5 kW at half load | ~50,000 BTU/hr | ~8.6 hr | ~43 hr |
| Home furnace | ~100,000 BTU/hr | ~4.3 hr | ~22 hr |
Enter your appliance's own BTU rating in the calculator above for an exact figure. In Canada, propane is sold by the litre and cylinders are marked in kilograms: a standard 20-lb BBQ tank is a 9-kg cylinder holding roughly 18 litres when full. Use the calculator's L option to work in metric directly.
Common mistakes
- Wrong tank size: using full tank size instead of actual usable propane.
- Ignoring cycling: forgetting that appliances cycle on/off rather than running continuously.
- Mixed units: confusing lb vs gallons vs litres in your calculation.
- No reserve: not keeping a spare tank on hand for backup.
FAQ
How many pounds are in one gallon of propane?
About 4.24 pounds per US gallon.
Is this exact?
No. Real usage varies with temperature and appliance efficiency.
How long does a 20 lb propane tank last?
About 18 to 20 hours on a medium-sized grill (10,000 to 15,000 BTU/hr), 8 to 10 hours on a large grill (30,000 BTU/hr), or 12 to 18 hours on a portable generator at half load. For a propane heater rated at 30,000 BTU/hr, a 20 lb tank lasts roughly 14 hours of continuous run time. The calculator gives an exact number once you enter your appliance's BTU rating.
Does propane work in cold weather?
Yes, but with caveats. Propane vaporizes reliably down to about -44 °F, so the fuel itself works in almost any US climate. What fails first is the tank's ability to supply vapor fast enough, below 20 °F, a small 20 lb tank can't keep up with a high-demand appliance (over 60,000 BTU/hr), causing pressure drop and a weaker flame. Solutions: use a larger tank, manifold two tanks together, or pick a 100 lb tank for winter use.
How do I tell how much propane is left in my tank?
Three practical methods: weigh the tank and subtract the 'tare weight' stamped on the collar (typically 17 to 18 lb empty for a 20-lb tank, so a full tank weighs 37 to 38 lb). Pour warm water down the side, the metal cools rapidly wherever propane is still inside, and you'll feel a clear cold line marking the level. Or install a magnetic or dial gauge on the tank valve. External sight gauges on larger residential tanks (100 lb and up) are most accurate.
How much propane does a whole-house generator use?
A 20 kW home standby generator burns roughly 1.5 to 2 gallons per hour at half load (per Generac's published fuel tables), or about 35 to 48 gallons per day of continuous running. Because usable capacity is around 80% of a tank's rated volume, a 100-gallon tank gives you roughly 40 to 55 hours, and a 500-gallon tank about 8 to 11 days. Actual burn is usually lower since the generator throttles down when household demand drops. Standby units draw far more than a cylinder can supply, so they run off a bulk tank, not a 20-lb BBQ cylinder.
Sources & references
- U.S. Energy Information Administration for propane energy content (~91,500 BTU per gallon, ~21,600 BTU per pound).
- Generac fuel-consumption tables for standby generator propane burn rates.
- Propane Education & Research Council and Ready.gov for storage, cold-weather, and emergency-fuel guidance.