Although it is found many times that tankless water heaters provide great energy-saving capability so it performs 1.5 times better than large tank gas heaters but then even we need to fill them back at the proper time.

Providing great energy is another thing but since it has a smaller volume of fuel gas (propane) present inside it, it’s important to know how much adequate amount of propane should we need in our powerful tankless water heater.

So here we are to help you calculate your usage according to some factors that matter while answering this question.

Some Best Tankless Heater Options

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What are those factors that we have to look upon?

The factors we have to look upon are the number of persons in a particular place of installation of the heater, temperature of the area where we are using the heater, and the type of water present in the locality(Soft or Hard).

Calculate propane usage tankless water heater

If these factors would not be the problem the calculation of the usage of propane must be direct. Since propane is taken in gallons in the US, We can simply calculate the amount of propane heater is using by knowing the BTU per hour rate of the heater.

One gallon of propane burning produces 92,000 BTU units per hour so we can get the amount by dividing the BTU units of the heater by 92000 BTU(the BTU units per hour in 1-gallon burning propane) and multiply it with the number of hours we need the heater in use.

Amount = Tankless water heaters BTU level / 92,000 x no. of hours heater is running


Temperature is a very important factor in knowing the amount of propane heater is using. If the temperature of a certain place is low it will take much more time of usage of the heater, using more energy produced by the fuel which is here in our case is propane.

Therefore lesser the temperature of place more will be the consumption of propane to make the much cooler water warm enough.

The places with a higher average temperature will need less amount of propane in comparison with the places with lower average temperatures.

Here, with the temperature of places also we cannot perfectly calculate the amount of propane the tankless water heater requires since with temperature we can just predict that the consumers will increase or decrease its use time according to their comfort level with the temperature of the water. But here we don’t know surely how many times a day or months we will use the water heater.

So here we cannot tell it accurately with the above-given formula because it does not take the temperature in its input.

Number of People

The number of people in a stay or any place where this tankless water heater runs also plays an important role in knowing the usage of propane. More the number of users, much of the propane we need to generate that energy to warm up the water.

No. of personsPropane requirement (in gallons)

Here is a table showing how much propane does a family of particular members need monthly in a gallon. Accordingly by taking the idea from this table, one can calculate their monthly uses of propane. For this one should just have to know the number of members in the family using the particular water heater.


Some places are there which have a supply of hard water due to the presence of some undissolved salts in water. To make the water soft one has to heat the water, which also needs energy coming from the burning of propane gas. If the place has soft water then the consumption of propane will be automatically low because it will not need that much warming up of water.

Also if we look into the other side, heating up water is not only the solution for softening the water. We can soften the water by using alum also. Hence it is not compulsory to consider this factor for calculating the amount usage of propane but in some cases, we can include it.

Frequently Asked Questions


Though we have the formula given above to calculate the amount of propane our tankless water heater is using, due to the presence of some other factors like temperature, the number of consumers, hardness, and many others.

So as a solution we say that one should calculate or get to know the amount of propane the water heater is using by observing and making the record of its use in the home, offices, or wherever it is running.

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