How long will a 100 pound tank last on a 15000 btu wall heater?

To estimate how long a 100-pound propane tank will last with a 15,000 BTU wall heater, you first need to know that propane contains about 91,500 BTUs per gallon, and there are approximately 37 gallons in a 100-pound tank. This results in about 8.8 million BTUs total. If the heater runs continuously at 15,000 BTUs, the tank would last roughly 8.8 million BTUs ÷ 15,000 BTUs/hour = about 586 hours. However, actual usage may vary based on heating cycles and efficiency.