Propane Tank Size Calculator (by appliance load and winter temperature)
The smallest standard tank that can vaporize enough propane for your appliances on your coldest days.
What size propane tank do I need?
Read down your coldest-day temperature to the first tank that meets your total appliance load. Values are Btu/hr, intermittent load, tank half full.
| Temperature | 150 gal | 250 gal | 500 gal | 1000 gal |
|---|---|---|---|---|
| 40°F | 214,900 | 288,100 | 478,800 | 852,800 |
| 30°F | 187,000 | 251,800 | 418,600 | 745,600 |
| 20°F | 161,800 | 216,800 | 360,400 | 641,900 |
| 10°F | 148,000 | 198,400 | 329,700 | 587,200 |
| 0°F | 134,700 | 180,600 | 300,100 | 534,500 |
| -10°F | 132,400 | 177,400 | 294,800 | 525,400 |
| -20°F | 108,800 | 145,800 | 242,300 | 431,600 |
| -30°F | 107,100 | 143,500 | 238,600 | 425,000 |
Worked example
A home with a 100,000 Btu/hr furnace, a 40,000 Btu/hr water heater, a 35,000 Btu/hr range and a 25,000 Btu/hr dryer has a total load of 200,000 Btu/hr. If the coldest days average 0°F, PERC Table 5 gives 134,700 Btu/hr for a 150-gallon tank and 180,600 for a 250, which are both too small, and 300,100 for a 500-gallon tank. So the 500-gallon tank is the smallest that fits. At 91,500 Btu per gallon, running everything at once burns about 2.2 gallons an hour.
How it works
A tank has to boil off propane as fast as your appliances burn it, and it does that more slowly in cold weather and when the tank is low. PERC Table 5 gives the most a tank can deliver without frosting, assuming it is half full, aboveground, at 70% humidity and under intermittent load. Under continuous load, multiply by 0.25. Add the input ratings from each appliance's nameplate. Your supplier sizes the final tank and also weighs how many gallons you use a year and how often they deliver.
Questions
What size propane tank do I need for a whole house?
It depends on the load and your winter. At 0°F, a 500-gallon tank supplies up to 300,100 Btu/hr and a 1,000-gallon tank 534,500 Btu/hr (PERC Table 5).
Why does temperature matter?
Propane vaporizes more slowly in the cold. A 250-gallon tank supplies 288,100 Btu/hr at 40°F but only 145,800 at −20°F.
How much propane does an appliance use per hour?
Divide its Btu/hr rating by 91,500 Btu per gallon (PERC Table 1C). A 100,000 Btu/hr furnace uses about 1.1 gallons an hour at full fire.
Sources
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