Propane Tank Runtime Calculator

How Long Will Your Propane Tank Last? Complete Runtime Guide

Propane is one of the most versatile emergency fuels available. Unlike gasoline, it stores indefinitely without degradation. Unlike diesel, it's readily available in portable tanks at hardware stores, gas stations, and grocery stores. Whether you're running a generator, staying warm with a propane heater, or cooking on a camp stove during an extended power outage, understanding propane consumption is essential for emergency planning.

Propane Tank Basics: Sizes, Capacity, and BTU Content

Before calculating runtime, you need to understand what you're working with. Propane is measured in pounds, gallons, and BTU (British Thermal Units). Here's how they relate:

• 1 pound of propane = approximately 21,500 BTU
• 1 gallon of propane = approximately 91,500 BTU
• 1 gallon of propane = 4.2 pounds

Common Propane Tank Sizes

Important: The tank weight listed (20 lb, 30 lb, etc.) refers to the propane capacity, not the total weight. A full 20 lb tank weighs about 38 lbs including the tank itself. The "tare weight" (empty tank weight) is stamped on the tank collar.

The Propane Runtime Formula

Calculating propane runtime is straightforward once you know your appliance's BTU consumption:

For a 20 lb propane tank (430,000 BTU) with a 30,000 BTU heater:

430,000 BTU / 30,000 BTU per hour = 14.3 hours

However, real-world runtime is typically 10-15% less due to:

• Appliance efficiency (not all BTU converts to useful output)
• Cold weather reducing tank pressure
• Tanks not being 100% full (filled to 80% for safety)

Propane Consumption by Appliance Type

Propane Generators

Propane generators consume fuel based on their wattage output and load. Unlike gasoline generators, propane generators produce about 10% less power per BTU but offer cleaner operation and longer storage life.

Propane Heaters

Propane heaters are rated by BTU output. Most have adjustable settings, so actual consumption varies. A 30,000 BTU heater on medium might only use 15,000-20,000 BTU per hour.

Cooking Appliances

Propane cooking is highly efficient for emergency use. A camp stove uses relatively little fuel and a single 20 lb tank can provide weeks of cooking capability.

How Many Propane Tanks Do You Need?

For emergency preparedness, calculate your needs based on hours of use per day and outage duration:

Generator Use (8 hours/day at 50% load)

• 3-day outage: 2-3 twenty-pound tanks
• 7-day outage: 5-7 twenty-pound tanks
• 14-day outage: 10-14 twenty-pound tanks

Heating Use (12 hours/day with 18,000 BTU heater)

• 3-day outage: 2 twenty-pound tanks
• 7-day outage: 4 twenty-pound tanks
• 14-day outage: 7 twenty-pound tanks

For long-term preparedness, consider a 100 lb tank or larger. One 100 lb tank equals approximately five 20 lb tanks and is more cost-effective per pound of propane.

Propane Storage Best Practices

Safe Storage

• Store tanks upright at all times
• Keep outdoors or in a well-ventilated area
• Away from ignition sources, air intakes, and living spaces
• Protect from direct sunlight in extreme heat
• Never store inside vehicles, basements, or near furnaces

Maintenance

• Check valves and connections annually for leaks (soapy water test)
• Tanks require recertification every 12 years (check date stamp)
• Replace damaged or rusted tanks immediately
• Store with valve closed and cap in place

Cold Weather Considerations

Propane doesn't freeze, but tank pressure drops in cold weather. Below 40F, propane vaporization slows. Below -44F, propane won't vaporize at all. In cold climates:

• Use larger tanks (more surface area for vaporization)
• Keep tanks as full as practical
• Shield tanks from wind but maintain ventilation
• Consider a tank heater for extreme cold

Propane vs. Gasoline for Emergency Generators

For emergency preparedness, propane's indefinite storage life and safer handling often outweigh the slightly higher operating cost. A dual-fuel generator offers the best of both worlds.