How Much Gas Does a Generator Use? (Fuel Consumption)

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You can save a lot of money by thinking in advance about generator running costs. And when we say in advance, we mean even before you buy a generator. The reason for this lies in the fact that the type of generator and the fuel you choose will have a direct influence on how much money you’ll need to set aside for hourly, daily, monthly, and yearly use. So, to set yourself up for budgeting and saving success, think about generator fuel consumption on time.

Unfortunately, generators are not a one-time cost. After you figure out the best type, brand, and model for you, you’ll need to pay for the fuel. Let’s discuss everything you need to know to make the most pocket-friendly decision about your next generator. 

How Much Gas Does a Generator Use?

Three main factors will determine the cost of running a generator:

  • Type of fuel
  • Type of generator
  • Amount of load

The load is a significant factor in this calculation. If you’re planning to run your generator once in a while during a power outage, then you probably won’t spend a lot of money no matter which type of generator and fuel you use. But if you are a frequent user, you want to think about the other two factors.

Your decision on the type of generator will be influenced by your needs the most. If you like camping, you’ll go for a portable generator. On the other hand, if you want backup power to run your entire house, you’ll probably decide on a standby generator. In any case, you should be aware that a particular type of generator is more or less efficient depending on the fuel you use – more on this below.

Fuel costs and characteristics vary based on your needs and situation. A fuel type that costs more may turn out less expensive for you in the long run, while the cheapest option may be heavy on your wallet. There are a lot of factors to consider here, so let’s review them. 

generator fuel consumption

Generator Running Cost by Fuel Type  

There are four most common fuel types you can run your generator on. Not every generator is compatible with every fuel type, so it’s essential to think about each fuel’s characteristics, pros, cons, and cost before committing to it. Let’s look into all fuel types and give some examples of how much gas is necessary.

Gasoline

Let’s start with the most common type – gasoline generator fuel consumption. For example, the gas consumption of a 7500-watt generator will typically be around 1.2 gallons of fuel per hour, and a 5000-watt generator will typically consume about 0.75 gallons per hour at full load. If you’re interested in less power, a 3500-watt unit running at half load will run just under 2 hours on 1 gallon of gasoline.

The reason why gasoline generators are the first choice is that they tend to be more affordable. It also sounds like a logical and familiar choice since most people use gas in their cars, lawnmowers, etc., which means the leftover gas can be repurposed.

On the flip side, you can’t store a lot of gasoline in one place since it’s highly flammable, and it will also go stale pretty quickly if you don’t find a way to use it. Moreover, gasoline is not always available in emergencies. With that being said, gas is a good option when it comes to cost for those that seek a short-term power supply.

Propane

Another very common option on the market is propane generators. Liquid propane has many benefits, and you can also find dual fuel generators which you can run on both propane and gas.

How much propane does a generator use per hour will again depend on size and load. A 5000-watt propane generator consumes about 0.96 gallons per hour. An 8000-watt generator burns 1.55 gallons per hour, while a 22 kW generator would need 3.6 gallons of propane per hour. If you have a 20-lb propane tank, you can expect to run your generator for about 6 hours. This, of course, depends heavily on the load.

Unlike gasoline, you can store propane in bulks for a long time, making it highly convenient for people living in remote areas or those that have frequent power outages and need to have fuel available at all times. It’s also safe to store, can last for years in the original tank, and unlike diesel, has the added benefit of burning cleaner, therefore, polluting your environment less.

Another convenient thing is that you can connect one propane tank to another. This means you have to tend to your generator less frequently than when running on gasoline or diesel, which are limited by their fuel tank capacity. Keep in mind that a 100-lb tank does cost more, but you’re paying less for a gallon than when you get a 20-lb tank. So the size of the tank can influence the cost considerably, and it’s less expensive to use a larger tank.

On the other hand, propane generators are more expensive, and they produce 30% less heat than gasoline generators, making them less efficient. Also, if you use your generator occasionally, it doesn’t make sense to buy and store propane in bulk just because it’s cheaper.

Diesel

Diesel fuel is a bit less common than gasoline and propane but still used by many. When it comes to diesel generator gallons per hour spent, the amount is less than with gasoline. A 10000-watt generator burns roughly 0.88 gallons of diesel per hour. A 15 kW diesel generator fuel consumption is about 1.2 gallons per hour, while a 20 kW unit working at full load consumes around 1.6 gallons per hour.

As you can see, a diesel generator uses much less fuel per hour than a gasoline one. This is because diesel burns slowly. However, diesel is on the top when it comes to pollution. So you may be saving money on the one hand but losing clean air on the other. You should also expect to pay more for diesel generators and have a more challenging time maintaining and moving them since they tend to be bulky and heavy.

Natural Gas

Natural gas is used primarily in residential areas where there’s already installed supply. The most common natural gas-powered generators are standby generators. They are frequently used to power entire homes and businesses during power outages. The unit of measurement for natural gas is a bit different, and instead of gallons, cubic feet are used.

When it comes to how much natural goes a generator uses, a 15 kW generator will consume about 210 cubic feet of natural gas per hour. A 20 kW generator consumes 289ft³ per hour, and a 30 kW unit will use 416ft³ per hour at full load.

Natural gas generators have much lower fuel consumption levels. They burn their fuel much slower than other generator types. However, you can’t get natural gas in tanks or store it. The only way to use it is by having a constant supply nearby that you can connect to.

Learn more about the average runtime of generators in our in depth guide.

Average Price for Each Fuel Type

To make comparing fuel consumption and the average cost of fuel easier, here’s a visual representation of the information as mentioned earlier:

  Average fuel consumption by size*
Size3kW5kW7kW10kW15kW20kW30kW
Generator Fuel Consumption Per Hour**Gasoline (gallon) $3.550.40.751.01.52.253.04.5
Propane (gallon) $2.38***0.60.961.421.922.43.45.1
Diesel (gallon) $3.380.20.30.650.881.21.62.9
Natural Gas (cubic feet)
$0.0095****
5172110140210289416

*Please note that the chart indicates approximate fuel consumption by size, but it can vary depending on many factors, including the model of your generator.

**Cost of fuel as of October 2021.

***Propane costs between $2 and $2.75 on average, so the average of this was taken.

****Due to lower production, natural gas prices increased in 2021.

Let’s compare running a 20-kilowatt hour on various fuel types. Running it on gasoline would cost you $10,65/hour and $255/day. Propane would cost you $8.2/hour and $197/day. Using diesel would amount to $5,40/hour and $130/day. Finally, using natural gas would amount to $2.75/hour or $66/day.

Generator Running Cost by Generator Type  

Generator consumption and fuel efficiency may depend on the type of generator as well.

Inverter Generators

Inverter generators are very popular for smaller devices and appliances. They have a very valuable feature that influences cost – the economy mode. This mode regulates how much gas is used depending on the demand, making portable inverter generators the most fuel-efficient in this respect.

Additionally, you can parallel generators and use two smaller units instead of one large unit, which would get you more power and save fuel. If you’re a fan of gasoline, an inverter generator can run for 8 to 10 hours on 1 to 2 gallons, making them far more efficient than portable generators. However, keep in mind that inverter generators cannot run an entire home and their size range on the market is still limited.

Portable Generators

Portable generators come in various sizes, and the cost of running one can vary a lot depending on the size and the load. They do have a higher fuel consumption than inverter generators, so they are not as affordable to run. Also, keep in mind that the runtime of most portable generators depends on their built-in gas tank capacity.

Standby Generators

A standby generator is used by those in need of a lot of electrical power, whether to power large appliances or even run an entire house. As such, standby generators are more expensive to run, but they offer much more than portable or inverter units. 

You can also compare the prices of each generator type in our dedicated article.

FAQ

How much fuel does a generator use? 

Generator fuel consumption varies substantially depending on the generator size, load, and fuel. You can spend anywhere from 0.50 to 7 gallons of fuel, depending on the various factors.

How much does it cost to run a generator?

The cost of running a generator depends on the amount of fuel you use, the generator size, and the load. You can spend around $1 per hour with a 7000-watt natural gas generator or $14.5 running a 35 kWh propane generator.

How much does it cost to run a generator for a day?

The cost of running a generator for a day depends on the wattage and the load. It can cost anywhere from $60 for smaller units, all the way up to several hundred dollars for large ones. Fuel type also plays a role, with propane being currently most pocket friendly, unlike gasoline.

How much fuel does an RV generator use?

The amount of fuel an RV generator uses depends on the type, size, and load. In general, you’ll need at least 4000 watts to power essential things in your RV. If you have a portable generator of this size, you’ll be able to run it for 10 hours at half load, consuming about 0.6 gallons of gas per hour.

How much does it cost to run a whole house generator on natural gas?

Running an entire home on natural gas with a whole house generator will require at least a 15 to 20kW generator. A 20kW generator fuel costs $66 per day, which amounts to almost $2000 a month.

What is the most efficient fuel for a generator?

Diesel burns slowly and hot, making it the most efficient fuel for generators. It produces 138,700 BTU per gallon of fuel. However, regardless of its efficiency, it’s not the most pocket- or eco-friendly option for everyone.

Final Thoughts

So, how much gas does a generator use? It varies so much depending on all the factors we covered, such as fuel type, wattage, and load in use. However, the good thing is that you can figure out a generator fuel consumption before making a purchase and making sure it makes sense for your situation and wallet.