How Much Propane Does A Tankless Water Heater Use?

Tankless water heaters are an excellent way to have hot water on demand. You never have to worry about running out of hot water. The downfall is that they use a lot of propane. So, how much propane does a tankless water heater use?

Most tankless water heaters use between 0.58 and 2.18 gallons of propane per hour of use. You can find out the exact amount of propane used by determining the GPM of your tankless heater and how often hot water is used throughout the day. Homeowners should know this information to figure out how much propane they will need. 

Different Types of Water Heater

It’s important to have an idea of how much propane a tankless water uses. This way you will be able to monitor your propane levels. Today, we’re going to break down how much propane a tankless water heater uses and everything else you should know. Read on to learn more.

How Efficient Is A Tankless Water Heater?

A great way to reduce your carbon footprint is by using a tankless water heater. This is because tankless water heaters use an average of 30% less energy than storage water heater tanks. Heaters with a higher energy factor rating are more efficient. 

Now, even though tankless water heaters are more energy efficient, they still use a lot of propane. There are a few factors that determine how much propane the heater uses. 

  • Energy efficiency rating
  • Size of the tankless heater
  • How much hot water is used 

On average, a household using a tankless water heater will use 1.5 gallons of propane per day. However, that average doesn’t apply to every situation. You might be wondering how you can get a more accurate estimate for your household. 

Figure Out How Much Propane Your Tankless Heater Uses

You may need to get your calculator ready for this part. You can calculate how much propane is being used by determining the energy content. So, what do you need to know to figure this out?

Let’s start with the propane. One gallon of propane is able to produce 91,452 BTU if the heater is running at 100% efficiency. The tankless water heaters are measured by GPM. Most tankless water heaters are between 5.3 and 11 GPM.

You will need to refer to your tankless water heater’s manufacturer’s instructions to determine your heater’s GPM and the amount of BTU it produces. 

Once you know this information, you can use the following formula to calculate how many gallons of propane are used per hour of usage.

  • Heater capacity in BTU divided by BTU per gallon (91,452) = Amount of propane used per hour

For example, a 5.3 GPM tankless water heater produces 53,000 BPM. 53,000 / 91,452 = 0.58 gallons of propane used per hour. 

How Much Does A Tankless Water Heater Cost To Run?

You will need to know the cost of propane in your area to determine how much it costs to run a tankless water heater. Multiply the cost of propane by the amount of propane used per hour to determine the cost to operate the heater.

Let’s take the example we used above. A 5.3 GPM tank running at 100% efficiency will use 0.58 gallons for one hour of use. If the cost of propane is $2.25 per gallon, you can use this formula to determine the cost:

  • 0.58 X 2.25 = $1.31 per hour

So, you might be wondering how this compares to the cost of running a hot water tank. A hot water tank heaters the water as it’s stored. On average, a hot water tank will run for 3 to 5 hours per day to keep the water supply hot for when it’s needed. 

The cost of a hot water tank will also depend on whether it’s an electric heater or powered by propane or gas. On average, it costs $0.62 per hour for propane-powered water tanks to heat up and $1.20 for electric water tanks. 

So, you may be thinking that hot water tanks seem more cost-friendly. That’s not the case at all. Tankless water heaters work on demand. This means that they only heat the water as you use it. If your household only uses 30 minutes of hot water in a day, that’s all you’ll pay for. 

How Much Propane Do The Other Appliances In Your House Use?

While we’re on the subject of propane, you might be wondering how much your other appliances use. After all, a homeowner should know how much propane they use each year. The average household uses 250 gallons of propane annually for their water heater. But what about other appliances?

If you determine the amount of BTU an appliance uses per hour, you can use the calculation we provided above to determine how much propane it uses in one hour of use. Let’s take a look at the average BTU of common household appliances.

ApplianceBTU Per Hour
Gas Stove65,000
Dryer20,000 to 25,000
Propane grills/ barbecues20,000 to 40,000
Gas fireplace7,000 to 60,000
Pool heater100,000 

Let’s say you use a 20,000 BTU dryer and put it on a 1-hour cycle. Here is how you can find out the exact amount of propane used.

  • 20,000 / 91,452 = 0.22 gallons of propane used 

What Does The Efficiency Of A Propane Water Heater Depend On?

Something we have mentioned several times throughout this article is efficiency. The efficiency of a tankless heater is measured by how much energy it takes for it to perform. The efficiency rating of an appliance is measured in percentage.

So, you might be wondering what factors into the efficiency of a propane tankless water heater. There are two things that play a major role, the size of the heater and the amount of water your household uses. Let’s take a look at what you should know.

Size Of Your Heater

There are different sizes of water heaters you can get. Tankless water heater sizes are determined in GPM. This stands for gallons per minute. Now, gallons per minute doesn’t refer to how much propane is used. This is for how much water the heater can heat.

That being said, smaller tankless heaters will use more propane than larger heaters. This is because smaller heaters will need to work harder to keep the water at a consistent temperature. 

For example, a 7 GPM heater will use more propane to keep a shower hot for 30 minutes than a 10.5 GPM heater will need. This is because the larger heater will allow more water in at once to heat.

How Much Water You Use

You play a big role in how efficient your tankless water heater is. This is because the amount of water used on a daily basis will determine how hard the heater needs to work. A household that only uses 40 minutes of hot water a day is more efficient than a household using 90 minutes.

The biggest difference between tankless water heaters and storage water tanks is that hot water is supplied on demand. A storage water tank will keep the water hot no matter how much you use. On the other hand, the tankless water heater will only use energy to heat the hot water being used.

This is one way to look at it. If a household with a storage water tank goes out of town for the weekend, the water tank heater will still use energy to keep the water at a consistent temperature even though no taps are being used.

Now, apply the same scenario to a household with a tankless water heater. Their water heater won’t use any propane while they’re away because they didn’t use any hot water. 

Is A Propane Or Electric Water Heater More Efficient?

Propane water heaters are more efficient than electric heaters. Making the switch from electric to propane is a great way to reduce the cost of your electric bill. On average, propane is 13 to 15% more efficient. 

This may not sound like a lot, but there are a few more things that you should consider. A tankless water heater cuts down on emissions by nearly 70%. Not only is this choice friendlier on your electric bill, but it’s also better for the environment.

There’s one thing that makes propane particularly more efficient than electric. That’s the amount of time it takes to heat the water. Often electric heaters will need a bit of time to reach the maximum temperature. Propane tankless heaters will have the hot water ready in an instant.


Tankless water heaters are the most efficient way to provide hot water for a household. Homeowners should have a rough idea of how much propane their heater uses. After all, you don’t want to run out of propane before you need to take a shower.

If you’re still using a storage-tank water heater, this is a great time to contact a local HVAC specialist about switching to a tankless heater. This way you can use less electricity and propane, allowing you to save money in the long run. 

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