How Much Propane Does A Tankless Water Heater Use 2022

Although propane tankless water heaters are an essential part of life nowadays, almost every one of us uses on-demand propane tankless water heater or any other heater because of the continuous hot water they offer. At the same time, how much propane does a tankless water heater use exactly is a frequently asked question? 

The question is not simple to answer as there are a lot of factors that are needed to consider while calculating the amount of propane gas a tankless water heater uses. Also, a propane usage calculator is necessary to determine the cost precisely without uncertainty.

Managing your gas bill and ensuring that you have enough fuel on hand is a top priority. But what about monitoring the propane usage of propane tankless water heaters?

Calculate Propane Usage Tankless Water Heater

Tankless water heater propane usage depends on the following three factors. After knowing these factors and their effects on the propane usage ability of propane tankless water heaters, it’s easy to calculate the end cost:

Size of a Heater

When it comes to energy efficiency, bigger isn’t always better. The 11 GPM 199,000 BTU propane tankless heater will use more of this valuable resource than a 7 GPM 75,000 BTU unit. 

How Water Capacity

Another important factor includes hot water generation per day. It means that a heater that runs for more time a day will use more propane gas than the one which runs for less time. For example, if you run your heater for 5 hours a day and 2 hours another day, it will cost more on the first day. 

Energy Efficiency

Propane instant water heaters are considered more efficient than the one which takes some time to turn your cold water hot enough to use for a shower. Again, a more efficient heater that offers instantaneous hot water is more likely to utilize than any other heater. 

Environmental Temperature

The LPG used by a propane instantaneous water heater also depends upon the environmental temperature to a greater extent. For example, if you live in the coldest regions, then a tankless water heater needs time to offer hot water.

People in colder regions like Minnesota need more time for their heaters when it comes to water. The average groundwater temperature is 37-42 degrees Fahrenheit (19 Celcius).

It would take your device an extra 5 – 10 minutes once the initial 40-minute cycle has passed before you can set the desired temperature range at 105 degrees onward; this assumes no power interruption occurs during that span.

When you’re living in a place with average temperatures of 65 degrees Fahrenheit or warmer, it can take hours for your water to reach the ideal temperature of 105 degrees. But when someone lives closer to the Southern 66-degree mark on Earth’s surface (not including humidity and wind), they only have about 30 minutes before their pipes run cold.

Rinnai tankless water heater temperature variations in different regions

Water Hardness Level

It is another factor necessary to consider, and most people neglect it. If your water is hard, then the heater will spend more propane gas. On the other hand, soft water will heat up quickly, and hence it spends less propane and ultimately saves your cost.

Average Cost a Tankless Propane Water Heater Demands

Hence, the average cost of propane is $2.41 per gallon, which is not expensive so far. However, the final and accurate cost still depends on the factors given above. Also, an average person spends 200 gallons of water per year if he does not hold a large family or group of people around him. It means the total cost of investing annually on propane is $482 on average. 

Again it’s not a final cost; the above factors must be considered. Of course, if you have a large family group, then your annual propane usage cost may proceed by triple bounds or more. 

How To Calculate Propane Usage Tankless Water Heater?

It’s not simple to calculate the propane usage of a tankless water heater. Some steps and the points which are necessary to follow are given below:

Step#1: Understanding Propane Measurement

When you bring propane to fill the energy need of your tankless heater, what is the preferred method? Most people answer about the gallons as they measure it in gallons per minute or other units. On the other hand, many people bring this gas to their home simultaneously, i.e. get it for an entire month.

So, the first and the basic steps are learning the propane measurements, i.e. how much your tank can absorb propane amount. It helps not only to measure the amount of propane but also to measure the energy costs at the end. 

Step#2: Learn Your Tankless Water Heater

Each of the heaters runs in British Thermal Units. So, you should know about these units. If the BTUs units show high values, it means your water is hot than usual. In that case, you should understand that your water heater is consuming more propane amounts.

The most straightforward example to understand is if your water heater shows 110 BTUs on one day and 50 BTUs on the other day, the heater spends more propane gas on the first day. 

Step#3: Analyzing Water Heater Usage

Analyzing your water heater usage is very important. You don’t get any idea and will end up without knowing water heater usage. For example, if you know how every man at your home has taken the number of showers per day, easy it is to see the propane used by the tankless water heater.

For this purpose, you can guide everyone at your home to mention several showers per day or week on a sheet or aboard. This adds easiness in determining your hot water needs as well.

If you have a large family size, then on average, 90-100 gallons per water are used in a day, including shower, dishes, and cloth washing. You can also use a screen to monitor the total amount of water used per day at your home. Ultimately, it helps calculate an estimated amount of propane gas used per day. 

Step#4: Determine GPM of Tankless Water Heater

It is also an important step that helps you know the gallons per minute of water use. The warm is water means more propane gas will be used. Our recent experiment shows that most people at home set an average temperature range of 120degree F. 

After knowing the GPM rate of a heater, it’s even easy to decide which tankless heater could be a perfect match for your daily water needs. Rinnai heater has a GPM rate of 6.5GPM, which is good on average compared to other tankless heaters. They may either have too high or too low a GPM rate.

Step#5: Now Add all the Calculations

The last and most critical step is doing the calculations at the end; as we mentioned above, a 4.3 GPM tankless water heater produces 258 gallons per hour. But if you spend only 1000 gallons even a day, it means that you can quickly get the required amount of water in 20-24 minutes. 

Now divide the total number of BTUs in the water heater by one gallon of BTU and then 

multiply it with the total hours used to generate the required water amount. And in this case, the propane gas used per day is about 0.66 gallons in total. It is calculated by multiplying the total BTUs by hours. 

Hence, these are the steps that make you calculate the total propane gas used by a water heater. However, it’s not easy to figure it out. However, by just providing a little attention and spending some time, it’s dead easy to calculate propane gas used in a day and hence in a month. 

Watch this complete video to know more about the total propane cost of a tankless water heater!

Note: there is some tankless water heater BTU calculator that you can buy from the market to measure units.

Frequently Asked Questions

How big of a propane tank do you need for a tankless water heater?

It depends upon your tankless water heater size. However, 120 propane gallons is enough if you have a small family size. In other cases, you need a bigger size tank.

How much does it cost to run a propane tankless water heater?

$350 per year is the total amount that a propane gas tankless water heater consumes.

Is propane safe to use on my tankless water heater?

Yes, it’s safest to use because it emits less harmful gases. On the other hand, it provides more hot water in less time.

What is the typical size of a residential propane tank?

Five hundred gallons is the typical size of a residential propane tank.


The process of calculating propane usage on your tankless water heater can be a lot. But it doesn’t have to feel like you’re struggling through square roots with one hand tied behind your back! We’ve resolved this issue by gathering all the scattered info, so now monthly budgeting for gas should not take up much time at all – unless any other expenses in life require attention. 

The easiest way to manage your propane usage is by tracking how much you use. You can easily calculate the sum when considering factors like outdoor temperature and humidity, but aspects will affect it even more.

Make sure not only do these two matter in determining an accurate count for yourself – other things such as cooking style may come into play too, so do some research before getting frustrated over calculations or wondering why they’re wrong every time someone else asks about fuel levels.

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Bella Rose
By Bella Rose

Hello Everyone! I'm Bella Rose. I believe in spending wisely when it comes to knowing about home and kitchen appliances. Spend smartly and make your home smart.

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