How Long Will a 20 lb Propane Tank Last on a Generator?

The duration a 20 lb propane tank will last on a generator depends on the generator's fuel consumption rate, which is typically measured in pounds of propane per hour. Understanding the tank's duration and fuel efficiency is crucial for planning and managing your backup power needs effectively.

Fuel Consumption Rate

Most portable propane generators consume between 0.5 to 1.5 pounds of propane per hour, depending on the load and model. This rate is essential for estimating how long your 20 lb tank will last.

Calculating Duration

Here is a step-by-step guide to calculating the duration based on your generator's fuel consumption rate:

Basic Calculation: For a generator that consumes 1 pound of propane per hour, a 20 lb tank would last about 20 hours.
Example Calculation:

Duration 20 lbs / 1 lb/hour 20 hours

Higher Consumption Rate: If your generator consumes 2 pounds per hour, the tank would last about 10 hours.
Example Calculation:

Duration 20 lbs / 2 lb/hour 10 hours

Specific Generator Efficiency: Check your generator's specifications for its specific fuel consumption rate to get a more accurate estimate.

Propane vs. Gasoline Equivalence

Propane, also known as LPG (liquefied petroleum gas), is a popular fuel for portable generators. It is often compared to gasoline in terms of energy content and usage. To help you understand the duration, you can consider the following conversions:

1 gallon of LPG is equivalent to 0.74 gallons of gasoline (Gallons Equivalent, GGE). 20 lbs of propane is about 4 gallons LPG, which is roughly equivalent to 3 gallons of gasoline.

The primary advantage of LPG is that it does not deteriorate and does not clog a carburetor, making it ideal for long-term storage without special procedures.

Advancements in Diesel Generator Usage

I couldn’t find specific data for a 10kW propane generator, so we will rely on general calculations to provide an estimation of its fuel consumption.

According to several manufacturers, a diesel generator uses about 1 liter of fuel per hour when there is no load and up to about 3 liters per hour at full load. Here's how these figures can be converted to propane for a more accurate estimate:

Energy Content Conversion:

1 liter of diesel fuel contains about 38 MJ (megajoules) of energy. 1 liter of LPG contains 25 MJ of energy.

Efficiency Assumption: Assuming that the efficiency of a diesel generator is comparable to that of a propane generator, we need 38/25... about 1.5 times as much LPG by volume as we’d need diesel.

Estimated Fuel Consumption:

1.5 liters per hour when idling 4.5 liters per hour when loaded

Weight Conversion: 1 liter of LPG weighs 0.51 kg, which is 1.12 lbs. Therefore, 1.7 lbs of propane per hour when idling and 5 lbs per hour when loaded.

Conclusion: Your 20 lb tank will probably run that generator for between 11.7 hours when idling down to 4 hours when fully loaded. However, because we don’t know the relative efficiency of a propane versus diesel generator, this is not going to be an exact answer.

Understanding these factors can help you choose the right fuel and manage the duration effectively, ensuring a reliable backup power source for your needs.