A 100 lb propane tank typically lasts between 25 to 30 hours when used for heating or cooking, depending on the appliance’s BTU consumption.
A 100lb propane tank is a popular choice for heating homes, powering appliances, or running generators. But how long it lasts depends on usage, appliance efficiency, and environmental factors. This guide breaks down everything you need to know.
How Much Propane Is in a 100lb Tank?
A 100lb propane tank holds about 23.6 gallons of propane when full. Since tanks are filled to 80% capacity for safety, you get roughly 18.9 usable gallons (100 lbs ÷ 4.24 lbs per gallon).
Propane BTU Content
Propane contains about 91,500 BTU per gallon, meaning a 100lb tank stores approximately 1,730,000 BTU of energy.
How Long Will a 100lb Propane Tank Last?
The lifespan of a 100lb propane tank varies based on usage:
| Appliance | BTU Rating | Estimated Runtime |
|---|---|---|
| 75,000 BTU Heater | 75,000 BTU/hr | ~23 hours |
| 50,000 BTU Furnace | 50,000 BTU/hr | ~34 hours |
| 30,000 BTU Water Heater | 30,000 BTU/hr | ~57 hours |
| 10,000 BTU Generator | 10,000 BTU/hr | ~173 hours |
Home Heating Example
If you use a propane space heater rated at 75,000 BTU for 3 hours a day, a 100lb tank will last about 7-10 days.
Whole-House Usage
For a home using propane for heating, water heating, and cooking, a 100lb tank may last 2-4 weeks, depending on climate and efficiency.
Factors Affecting Propane Consumption
1. Appliance Efficiency
High-efficiency appliances like tankless water heaters use less propane than older models.
2. Outdoor Temperature
Colder weather increases propane consumption for heating.
3. Usage Patterns
Frequent hot water use or extended heating cycles will drain the tank faster.
When to Upgrade to a Larger Tank
If you’re refilling a 100lb tank more than once a month, consider upgrading to a 250-gallon or 500-gallon tank. Larger tanks reduce refill frequency and may qualify for bulk pricing.
For more details on propane heaters, check our guide on the best indoor-outdoor propane heaters.
Propane Safety Tips
- Never fill a tank beyond 80% capacity
- Store tanks upright in well-ventilated areas
- Check for leaks with soapy water
- Keep tanks away from open flames
For more technical details on propane vaporization rates, refer to this propane vaporization chart from Propane 101.
Final Thoughts
A 100lb propane tank is versatile but may not be ideal for whole-house heating. For occasional use or backup power, it’s a solid choice. For continuous heating, consider larger tanks or alternative solutions.
For more heating options, explore our guide on electric heaters that mimic wood stoves.
