Informational Guide

How Much Propane Does A Tankless Water Heater Use?

How much propane does a tankless water heater use exactly? Check out our complete guide to learn more about average usage & costs.

by Matt Moran

When you get a new tankless water heater, you want to know how much propane is used by it. That you, you know how much money you’re spending on fuel. The tankless heater is cost-efficient since it doesn’t need a lot of power to heat water.

If you want to learn more about how much propane you’re using, make sure to continue reading! So how much propane does a tankless water heater use? 

Tankless water heaters are energy and cost efficient. You’ll want to monitor your usage, however, to make sure that you're not spending more than you want to in a month. By making a budget and sticking to you, you can save and put the extra money where it needs to go. 

If you ignore it, you won’t know how much propane your family uses. If you have a larger family at home, you want to keep track of this information carefully. That way, you won’t overspend. You benefit by being more aware of your spending since you can make adjustments when needed. 

Factors That Affect Propane Consumption  

There are several factors that affect propane consumption. You'll want to keep track of this information. You can use an app or a simple notebook to keep records. It would be best if you did this over a long period. 

Hours Of Usage  

The longer you run your heater, the more propane it burns through to heat it. Plus, washing dishes, laundry, or using any hot water adds to the cost.

Write down the amount of time you spend using hot water, make sure other people in your home also add to the list. You’ll notice trends over time. 

Groundwater Temperature  

Some areas in the north have a much colder groundwater temperature. That means it takes a lot longer for the water to heat up. You'll likely need to run the water for a few minutes before it comes out hot - this also adds to your propane use. 

Hard Water  

If you have hard water, you’ll need to make sure that you use a water softener. Soft water is easier for the propane to heat, making it use significantly less fuel in the process.  

Household Size  

The amount of people in your family changes the propane consumption. A family of two is going to go through a lot less fuel than a family of seven! Especially if everyone takes at least one shower per day.

The family of two will use around 15 gallons of propane monthly, while the larger family could quickly burn through more than 50 gallons! 

Water Heater Capacity

Finally, the water heater capacity can impact the amount of fuel you use. The higher the gallon storage is, the more efficient it can heat the water.

Overall, larger tanks use less fuel because they store more hot water. Once water is made hot, it’s easier to keep it up to that temp. 

Wall Mounted Tankless Water Heater

How Much Propane Does a Tankless Water Heater Use? (Calculations & Costs Explained)

Every household is going to use a different amount of propane and hot water. You’ll need to calculate propane usage for a tankless water heater, but first, you need to know how much propane a water heater uses. It will depend on the size of your water heater. 

In general, the average home uses about 1.5 gallons of propane a day. This is based on a 40 gallon water heater running each day. However, you may want to find your precise amount. 

You want to calculate the amount of propane the heater uses by following the below formula: 

Propane Use = tankless water heater BTU level / 92,000 x number of hours unit runs 

This formula gives you the amount of propane you’re burning per day. Don’t be surprised if it comes out to be a lot higher than expected. If you think you’re using the average amount of water at home, then you can use the table below instead.  

No. of Persons 

Propane Requirement (Gal) 

Estimated Cost Per Month 

Estimated Cost Per Year 










35 - 40 

$70 - 80 

$840 - 960 

Can A Propane Tankless Water Heater Save You Money?  

You can save money installing a propane water heater, especially when compared to the other type of heaters. The best tankless options should run very efficiently. This is because propane is a much cheaper option than using fuel. Over time, those savings add up.  

You also get an improved efficiency, so you don't have to run the water heater for as long. That means you get more hot water for less money. Additionally, older electric hot water heaters lose efficiency over time. If yours is old, you're not getting a good value from it anymore. Propane heaters last a much longer amount of time.  

Man Doing Propane Calculation Costs

People Also Ask (FAQs)

Can a natural gas water heater be used with propane?  

You can't. Most appliances can work with either type of fuel, except for the hot water heater. This appliance only takes one or the other and can't switch to other types of fuel 

How long does a 500-gallon propane tank last?  

Most 500 gallons propane tanks should last you about five months. However, this is not counting for a furnace hookup, which uses the most propane in the home. 

How long does a 1000-gallon propane tank last?  

A 1000 gallon tank should last you about a year. This is based on the amount of time many people use the 500 gallon tanks. However, many large families can burn through these big tanks much faster. 

What is the best month to buy propane?  

Fall is the best time of year to save on propane costs. The weather is pleasant, and there's not as much demand for fuel. You'll want to do it in early fall, so you don't have to shop for propane in the cold. 


In short, it’s a good idea to monitor your propane usage of your tankless water heater. You can track expenses and build a budget based on how much you need. 

Matt is a freelance writer, English graduate, & keen traveler from the UK. As a specialist plumbing expert, he enjoys writing about everything there has to do with at-home plumbing products & related problems. When he isn’t writing, he’s usually drinking coffee or planning his next adventure. In his spare time, he also runs his own blog all about digital nomad life.