Generators stop working when they run out of gas. That’s why we looked into how long will a generator run on 5 gallons of gas.

Here’s the short answer:

A generator on 5 gallons of gas will last **anywhere from 6 hours and 42 minutes to 363 hours and 19 minutes.** The exact time primarily depends on generator size, and secondarily on the choice of fuel (gasoline vs. propane).

That’s quite a range. How to figure out how long will 5 gallons of gas last in a generator exactly? Well, we need to calculate a bit, based on several factors.

To help you out, we have prepared a **‘5-Gallon Tank Generator Running Hours Calculator’** where you can insert the *max. running wattage of your generator*, and *choice of fuel (gasoline vs. propane)*, and it will calculate how many hours such a generator lasts on a 5-gallon gas tank. Below the calculator, you will also find a **calculated chart** of how long does a 5-gallon tank lasts for 500W to 20,000W generators.

Here is what the calculator looks like (you can find it further on):

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

**Size of the generator**. A bigger 10,000W generator will run out of gas much faster than a small 2,000W generator.**Generator load.**If you run a generator on 100% output running wattage, it will burn through the 5 gallons of gas faster than if you would run it on 50% running wattage.**Choice of fuel:**1 gallon of propane can generate up to 91,500 BTUs. 1 gallon of gasoline can generate up to 124,000 BTUs. That means that a gasoline generator will run 36% longer than a propane generator (if we presume the same energy efficiency).*Gasoline vs Propane*.

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

### Energy Content Of Gasoline And Propane

Generators run on either gasoline or propane.

**5 gallons of gasoline** contain 620,000 BTU 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:* That’s enough to run a 10,000W generator for 18 hours and 10 minutes. If you have a smaller 2,000W generator, 5 gallons of gasoline can run it at 100% load for almost 91 hours; that’s almost 4 days.

**5 gallons of propane** contain 457,500 BTU of energy. That’s 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 smaller 2,000W generator can use that energy to run for 67 hours and 1 minute; almost 3 days.

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

## 5-Gallon Tank Generator Running Hours Calculator

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

### Calculated Table For Different Generator Sizes (5-Gallon Tank)

Generator Running Wattage: |
Gasoline Will Last For: |
Propane Will Last 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 Hours |

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, you can now adequately estimate how long will a 5-gallon tank run a generator.

If you have any questions regarding the calculations or your specific generator, you can use the comments below and we’ll try our best to help you out.

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