How Long Should 100 Gallons of Propane Last?

Propane usage depends on the nature of use, such as appliances, furnaces and fireplaces, as well as the climate. Each gallon of propane provides 91,547 British thermal units, or BTUs. Appliances can vary a great deal from about 25,000 BTUs per hour to more than 400,000 BTU per hour.

Actual usage of propane can be calculated by adding the BTU load of each appliance and then dividing by a 1-gallon BTU load of 91,547. It can also be calculated for each appliance. For example, a furnace with a BTU load of 200,000, which means that it uses 200,000 BTUs when operating at peak capacity, requires about 2.2 gallons of propane per hour, or 200,000 divided by 91,547.