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How Much Propane Does a Tankless Water Heater Use?

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How Much Propane Does A Tankless Water Heater Use

Are you one of those homeowners who use propane tankless hot water systems? Then, you might be wondering “how much propane does a tankless water heater use?” On average, propane burning in a tankless water heater produces 40,000 BTU per hour or 1.5 gallons per day.

Propane is a versatile fuel gas for household energy use, and it is widely known for its energy-saving capability. Calculating your propane usage will help you fully understand and analyze your annual energy consumption.

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Why You Should Determine Your Propane Usage


Tankless water heaters are instantaneous and more cost-efficient than conventional gas tanks. Out of many fuel gas choices in the market, Propane is the most energy-efficient alternative.

Typically, the usage amount varies in the frequency of water utilization. We have different families, and it goes to say that we also have multiple purposes for hot water. It is essential to monitor how the water heater is used, most especially in large households.

You can calculate your monthly propane usage easily with this simple tactic. The average cost per gallon of propane gas is 2.00 to 2.75 dollars. Sometimes, annual propane usage for the whole family can cost up to 100 dollars or more, depending on the simultaneous activities in the household.

You can intelligently create a budget plan for your propane consumption by observing your usage habit per month. Collecting this information is beneficial for you to calculate your overall propane expenditures.

Therefore, you can precisely budget your propane allowance monthly or annually for your tankless water heater.

Calculating Your Propane Consumption

When calculating your propane usage, you don’t need to do any complex mathematical computations. Don’t overwhelm yourself with the numbers. Here’s a simple tip: Always look for the number of gallons used per month.

In some parts of the world, propane is often measured both in liters and gallons, but I prefer using the latter because it is a lot easier. Propane production differs in tankless water heater units.

Most tankless heaters can deliver hot water at a rate of 2-5 gallons per minute. Some can even produce 9 gallons per minute. As stated by the US Energy Information Administration (EIA), a gallon of propane comprises 91,452 BTUs per hour.

You can use this information by taking your tankless water heater unit’s BTU rating and dividing it by 91,452. Follow this formula, and you’ll be able to determine the capacity of your water heater to use propane.

You might be wondering why there is a spike in the number of gallons of propane you use per month when you don’t do many home activities. It is because propane usage is often determined by different factors.

Factors That Could Affect Calculation of Propane Consumption


Hours of Usage

Of course, the longer you use your water heater, the more propane it needs to burn. Plus, different in-home activities need different levels of it. The hours will reveal what household chores maximize your propane tankless system.

For example, you could use a hot shower for 10 hours straight or longer, but it requires more propane burning to be as hot as the first 10-minute hot shower in the morning. The amount of propane used is influenced by the given GPM of several fixture types.

You have to figure out how many gallons per minute each of them uses to have an accurate idea of how much propane is needed per month. Kindly refer to the guideline list below.

  • Laundry 1.5 to 3.0 GPM
  • Washing Machine 2 to 3 GPM
  • Dishwasher 1.5 to 3 GPM
  • Shower 1.5 GPM to 3 GPM
  • Bathroom Sink 0.5 to 1 GPM
  • Kitchen Faucet 2 to 3 GPM

I would suggest listing down the times you run multiple fixtures simultaneously. Keep track of the times and the activities associated with them. Do this every week, and you’ll discover a pattern or routine of your propane usage.

Groundwater Temperature

It is undeniable that propane reduces energy costs for your family’s living expenses, but you still need to evaluate its overall energy efficiency. The first thing you should inspect is your location.

Before deploying your newly bought tankless water heater system in your residential home, always consider your location as one of the main factors of your propane conservation.

If you live in the cold northern region, it will take too much time to heat water. As a result, you will need more propane for your indoor water use.

Let’s say the default groundwater temperature in your area is 52 degrees Fahrenheit; then you would need a water heater that can increase it by 53 degrees Fahrenheit at 5 GPM capacity to attain well-heated domestic water.

Always remember that the colder the incoming water, the more heat it absorbs. Hence, you would need a cold-weather-ready water heater if you lived in colder climates. In general, the ambient temperature has an enormous effect on the burning production of propane.

Hard water

If the external source is hard, you will need to invest in a water softener. If your area has softer water, a higher amount of propane can be saved.

Household Size

I briefly mentioned this part earlier when creating a budget plan for propane consumption. The bigger the family, the higher the propane consumption is.

For smaller families, expect a smaller bill. A family of two members will use about 15 gallons each month, while a family of 5-6 members will use about 40 to 50 gallons each month.

Different household members have different activities. This thing alone contributes massively to the total amount of propane usage. Hence, it is necessary to take this factor into account since every family has a unique lifestyle.

Water Heater Capacity

Tankless water heater models have different water-saving technology. First, you have to look at the BTU rating. It will indicate how much propane is consumed per hour. Second, the flow rate is significant.

If your model has a higher gallon capacity, it will perform more efficiently when converting heated water.

This is because high-capacity systems can heat more water than low-capacity units in the same amount of time using the same amount of energy. It only means that the higher the GPM capacity, the lower the propane consumption is.

For instance, Rinnai RU130iP is a tankless water heater with superior energy efficiency. If you look into its specifications, it runs a 7 GPM mechanism, and it would surely meet your requirements about propane conservation.

Propane Usage and Cost Per Month

The minimum cost of a gallon of propane is only 2.00 dollars, but your monthly expenses are case-to-case. From my experience of living with my mom, we would only need to spend 33 dollars for propane per month.

That’s approximately 16 and a half dollars of propane per person. Compared to extended families, our propane budget is cheaper and cost-effective. If you have a family of 5 or more, expect to spend about a hundred dollars per month.

Propane usage depends on how each family manages their water heating needs. The more we use our water heater daily, the more propane is burned. Check the specs of your heater and use the formula I’ve provided to get the total usage amount easily.


Calculating the sum of your propane usage is easier than you think. If you are equipped with the correct information, you can easily manage your propane consumption. Always remember to consider the factors that affect your consumption. It will help you get a proper calculation.

Now you’re have the knowledge about how much propane does a tankless water heater use. If you are clueless about what kind of tankless water heater you should get, I would recommend units like Rinnai RU130iP. It offers greater energy efficiency compared to other conventional heaters.

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