How long will a generator last on 5 gallons of gas? (The calculator)

When the gas runs out, the generator stops working. So we looked to see how long the generator would last on 5 gallons of gas.

Here’s the short answer:

Generator will run on 5 gallon gas from anywhere 6 hours 42 minutes To 363 hours 19 minutes, The exact timing depends primarily on the size of the generator, and secondly on the choice of fuel (gasoline vs. propane).

That’s a lot of range. How to find out how long 5 gallons of gas will last in a generator? Well, we need to do a little calculation based on several factors.

To help you out, we have prepared a ‘5-Gallon Tank Generator Running Hours Calculator’ where you can join Maximum running wattage of your generator, And Fuel Choice (Gasoline vs. Propane), and will calculate how many hours such a generator lasts on a 5-gallon gas tank. At the bottom of the calculator, you’ll find a . will also get calculated chart How long does a 5-gallon tank last for a 500W to 20,000W generator.

Here’s what the calculator looks like (you can see it next):

How long will a generator last on 5 gallons of gas
Example: A gasoline generator with a running wattage of 5,000W on a 5 gallon gas tank will last for 36.33 hours.

The 3 most important factors that determine how long 5 gallons of gas will last in a generator are:

  1. generator size, A large 10,000W generator will run out of gas much faster than a small 2,000W generator.
  2. generator load. If you run a generator at 100% output running wattage, it will burn through 5 gallons of gas faster than if you run it at 50% running wattage.
  3. Fuel option: gasoline vs propane, 1 gallon of propane can generate up to 91,500 BTU. 1 gallon of gasoline can generate up to 124,000 BTUs. This means that a gasoline generator will last 36% longer (if we assume the same energy efficiency) than a propane generator.

To adequately calculate the running time of a generator on a 5-gallon gas tank, we first need to determine the energy content of both gasoline and propane:

Energy content of gasoline and propane

Generators run on either gasoline or propane.

5 gallons gasoline There are 620,000 BTUs of energy. If we convert BTUs to Watts (1 BTU = 0.293 Watts), we can get up to 181,660 Watts out of 5 gallons of gasoline.

Example: This 10,000W generator is enough to run for 18 hours 10 minutes. If you have a small 2,000W generator, 5 gallons of gasoline can run it at 100% load for about 91 hours; It’s about 4 days.

5 gallons of propane It contains 457,500 Btu of energy. That is, 134,048 watts of electrical energy.

Example: With a 5-gallon propane tank, we can run a 10,000W generator for 13 hours and 24 minutes. A small 2,000W generator can use that energy to run for 67 hours and 1 minute; approx 3 days.

Standard generators give 100% output all the time. Inverter generators, on the other hand, adjust power output to power draw; They will last longer on 5 gallons of gas.

5-Gallon Tank Generator Running Hours Calculator

Using this calculator, we can calculate how long a 5-gallon tank will last for different generator sizes:

Calculated Table for Different Generator Sizes (5-Gallon Tank)

Generator Running Wattage: For gasoline will run: Propane will run for:
500 watts 363.32 hours 268.10 hours
1,000 watts 181.66 hours 134.05 hours
1,500 watts 121.11 hours 89.36 hours
2,000 watts 90.83 hours 67.02 hours
3,000 watts 60.55 hours 44.68 hours
4,000 watts 45.41 hours 33.51 hrs
5,000 watts 36.33 hours 26.81 hours
6,000 watts 30.28 hours 22.34 hours
8,000 watts 22.71 hours 16.76 hours
10,000 watts 18.17 hours 13.40 hours
12,000 watts 15.14 hours 11.17 hours
15,000 watts 12.11 hours 8.94 hours
18,000 watts 10.09 hours 7.45 hours
20,000 watts 9.08 hours 6.70 hours

Hopefully, now you can get an adequate estimate of how long a 5-gallon tank will last the generator.

If you have any questions regarding calculations or your specific generator, you can use the comments below and we will do our best to assist you.


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