How Much Gas Does a Generator Use?

A gas generator can save the day during grid failures caused by bad weather. You can run fans, lights, and a refrigerator to stay comfortable and keep food from spoiling. 

Whether your generator uses gasoline, propane, natural gas, or another gas, all gases are expensive. So how much gas does a generator use dictates your fuel costs? 

Average Generator Gas Consumption Rate

“How much gas does a generator use?” doesn’t have one answer. How much fuel your generator burns will depend on several factors, including: 

  • The type of generator
  • The generator size or kilowatts
  • How much it’s powering
  • The fuel type

Each generator burns more or less gas depending on its type, size, kilowatts, the load placed on it, and the fuel type. 

Generator Type and Kilowatts

All the Residential generators fall into four general categories by application:

  • Portable recreational type, also known as RV generator
  • Portable generators
  • Inverter type
  • Home standby type, also known as the whole house type.

Portable Recreational Generator

These small generators are the type people might take to a campsite or remote location. You can use them during power outages, too. Most generators of this type weigh around 60 lbs. 

Portable recreational generators can generally handle up to 2,000 watts. This number could include a refrigerator, lights, or charging for a laptop or phone. 

Portable Generators

A large portable generator for household use can go as high as 7,500 watts during power outages. This size generator will power most things you need until the power comes back. 

These generators are portable with wheels that let you roll them into a garage. You don’t want to leave these out when you’re not using them. You can bring them and hook them up to your house when needed if the initial planning and preparation are already in place. A portable generator typically weighs around 300 pounds. 

Inverter Generator

The inverter generators come in various sizes. A midsize inverter can handle up to about 3,500 watts. You can power a refrigerator, air conditioner, or freezer and keep lights burning. These units can weigh as little as 150 pounds. 

A large inverter will also have wheels for portability and run up to 7,500 watts. These generators connect to a breaker panel instead of plugging into individual appliances.

If you plan to power many hard-wired appliances, an inverter is the best choice. 

Home Standby Generator

A home standby generator is also known as the whole house generator and sits outside much like a heat pump or air conditioning unit. A whole house generator connects directly to the home’s wiring system. If it runs on natural gas, it can connect to the home’s gas line. 

These generators don’t plug into appliances or need you to turn them on. A whole house generator will kick on automatically after a short delay following a power outage.

Standby generators can handle 20,000 watts or more. These units can power everything in the home. 

How Many Watts Do I Need?

The average home uses just under 11,000 kilowatts per hour for everything electrical. To power all your electrical appliances and lights in an outage, you’d need a generator that can handle that hourly load plus the higher starting wattage of some appliances like microwaves. 

If you want to run a generator to provide a backup power supply to your necessary appliances only, like the refrigerator, lights, or an air conditioner, you can calculate the typical generator size you need. Each appliance has a rating that tells you how many watts it uses. 

One kilowatt is 1,000 watts, so if you need a generator to handle 5 kilowatts per hour, you’d need to purchase a 5,000-watt generator. 

Types of Gas Compared

Many home generators use gasoline as a fuel source. You can also buy natural gas, diesel, or a propane generator. 

How much gas a generator consumes vary based on which fuel you use. For instance, diesel burns slower than regular gas, so you’ll use less. Propane gas, by comparison, burns much faster than gasoline. 

How much gas does a generator use if it burns gasoline vs. propane? How much does it cost to run the generator at full load? The answers depend on the going cost of fuel when you buy it, the type and size of the generator, how many appliances and lights you’re using the generator to power, and how fuel-efficient the generator is.

The ability to store a particular fuel depends on its oxidation and flammability properties and impacts fuel tank capacity and initial costs.

Gasoline Generators

The cost of running a gasoline generator varies widely depending on the average price of gas when you buy it. A gallon of gasoline can change in price by a dollar or two in a matter of a few months, so it’s impossible to predict the cost. 

Gas generators have better fuel efficiency than propane generators, so you will use a lesser quantity of gas than you would propane to produce as much power. To be prepared to use the generator in an outage, you’ll need to have it stored in a gas tank. You can’t go to the pump to get the gas in an outage because gas pumps use electricity.

You should add a fuel stabilizer to stored gasoline and keep it in an approved container with as little air as possible. If you store it improperly, the fumes can become a fire hazard, and the gas can break down and become unusable. 

In general, a 5-kilowatt gasoline generator burns about three-quarters of a gallon of gas per hour. Using only about half capacity or 2.5 kilowatts per hour will burn just over a third of a gallon. 

Diesel Generators

Diesel generators burn less fuel for the same power as gasoline generators, though it costs more per gallon. These units burn more efficiently and typically require less maintenance than standard gasoline-powered machines. 

These units often have much bigger tanks than gasoline generators, so you’ll need to refill them less. And diesel has a better storage life than regular gasoline. 

The generator will often be much noisier than a gas unit, which is something worth considering if you think you might need to run it at length.

As per the US Energy Information Administration, the standard generator requires about 0.08 gallons to generate a kWh of electrical energy.

A 10-kilowatt diesel generator will burn about four-fifths of a gallon per hour at total capacity, and a 20-kilowatt machine would burn about 1.6 gallons per hour. 

Propane Generators

You’ll burn more propane than you would gas or diesel in terms of volume or gas gallons, but the other advantages might make up for it. 

You don’t have to fill up at the gas station and worry about storing it since propane comes in sealed tanks. The tanks come in various sizes to buy and store more fuel easier than getting it from the gas station. 

If you buy a large propane tank, you can have propane delivered and stockpile for emergencies without the same concerns as gasoline.

Propane also stores well. Your fuel-stabilized gasoline might go bad after a year, but propane has an indefinite shelf life. It burns cleaner than gas or diesel, making propane-powered generators better for the environment and air quality.

You can also purchase a dual-fuel generator that will burn gasoline and propane to take advantage of the cheaper average cost of gas when it’s less expensive and the long-storing properties of propane. 

In our detailed guide on the subject, you may know about the fuel consumption in gallons per hour by a typical generator run on propane. As shown in the article:

  1. To feed a 2000 Watt load, the generator fuel consumption of liquid propane shall be 0.43 gallons per hour.
  2. A 10-kilowatt propane generator feeding an 8000-watt load will typically consume about one-and-three-quarters of gallons of gas per hour.

Natural Gas Generators

A Natural gas generator taps into the home’s natural gas lines, so you don’t need to store gas. 

These machines cost thousands of dollars to purchase, and installation can add thousands more. However, it’s a whole-home solution for people who want a seamless transition to generator power during an outage.  

How much natural gas does a generator use per hour

Fuel consumption in Cu.ft per hour of natural gas-powered generators is given by the formula

Fuel Consumption Per Hour = Generator Rated Wattage × % Rated Load × 7.43 Cubic Feet Of Natural gas ÷ 1,000

So a 5000-watt generator running at 60% load will consume 5000 x 0.6 x 7.43 / 1000 = 22.29 Cu.ft of Natural gas per hour. This calculation is based on a certain heat rate or efficiency value and is indicative. Heat rate is the actual gas used to produce 1 kWh of energy.

Natural gas has an efficiency of 29.4 to 44.8%. Depending on the efficiency of the fuel and the generator, the actual gas usage may vary.

How Much Gas Does a Generator Use?

To determine how much gas a generator will use, first check the manufacturer’s instructions and user manual for the generator. They typically give you reasonable estimates of fuel consumption at different levels of usage, so you can calculate how much you’ll really use.

For instance, a generator’s manual might indicate that it will run for three hours on a full tank of gas. This estimate might be for when you use the generator at a 50% load. By adding the wattage of all the appliances the generator powers, you can determine how many watts it supplies per hour. This number will tell you if you’ll burn less or more gas than the level mentioned in the manual.

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