How Much Propane Does a Tankless Water Heater Use? (+ calculator)


Are propane tankless water heaters true? propane guzzlers (still about 41% more economical than traditional tank water heaters). You’ll rarely find any propane-powered appliance that uses more propane than these on-demand heaters. How much propane does a tankless water heater use? Correct?

The amount of propane (and the corresponding dollar expense) depends on 3 major factors. These are:

  1. The size of a tankless propane tank. an 11 gpm 199,000 BTU Propane tankless heater apparently 7 GPM . will use more propane than 75,000 BTU unit, eg.
  2. Hot water production. A propane tankless water heater that runs 1 hour/day will cost more than the same unit operating for 20 min/day.
  3. energy efficiency. Propane on-demand hot water heaters are generally highly efficient. Propane burning efficiency (denoted by EF factor) starts at 80%. The most energy-efficient propane tankless heater has up to 99% energy efficiency (0.99 EF); These units use the least amount of propane for the highest hot water output.

Based on these 3 factors, we can calculate how much propane a tankless propane heater uses. Here’s a summary that illustrates propane use (we assume 100% production, 100% energy efficiency and a $2.41 average national price per gallon of propane):

  • smallest 53,000 BTU unit (lower level): 0.58 gallons of propane per hour. he is a $1.40/hour operating cost.
  • Largest 199,000 BTU unit (high end): 2.18 gallons of propane per hour. he is a $5.25/hour operating cost.

If you look at the Energy Star label, the standardized annual propane tankless heater use is set at 200 gallons. that’s about $482 per year. There is a wide range of how much it actually costs to run a propane tankless water heater per year.

By our calculations, here are the low-end and high-end costs:

  • lower level (53,000 BTU unit, 20 min/day, 0.99 EF): 71.22 gallons/year. that’s about $171.64 per year.
  • high-end (199,000 BTU units, 60 min/day, 0.80 eF): 992.80 gallons/year. that’s about $2,392.65 per year.

It doesn’t tell us much about how much propane does Our Using your own propane tankless water heater, right?

This is because some homes have smaller units, others have larger units, some homes use these propane on-demand water heaters for 1 hour per day while others only use them for 20 minutes per day Huh.

To help each person adequately estimate their unit’s propane use, we’ve created a Tankless propane usage calculator. You include the size of your unit, energy efficiency, and how many minutes per day you run your unit in BTU. You will get the calculator next.

Here’s what 40 minutes/day of use looks like for a 95,000 BTU (9.8 gpm), 0.95 EF propane tankless heater:

How much propane does a tankless hot water heater use?

On top of that, we’ve calculated how much propane tankless heaters of various sizes use per year, if you use them. 20 min/day, 40 min/day, And 60 min/day (Result summarized in table after calculation). This will give you a ballpark figure for how many gallons of propane your tankless propane uses per year.

Let’s first look at how everyone can calculate how much propane an instantaneous water heater uses:

How to Calculate Propane Usage for a Tankless Water Heater?

It is extremely difficult to heat water. This is due to the high specific heat (4.19 kJ/kg°C). Propane tankless heaters can heat water to over 10+ GPM in less than 15 seconds. This requires a huge amount of energy; All that energy is provided by burning propane.

To calculate how much propane these on-demand heaters burn to heat water, we need to know what the energy content of propane is.

NS US Energy Information Administration Here’s what helps us with this energy content: 1 gallon of propane = 91,452 BTU. This means that burning one gallon of propane produces 91,452 BTUs (at 100% efficiency).

Now, we have various sizes of tankless propane water heaters. If we take a look at Rinnai units (Rinnai produces the best propane tankless heaters; you can find them here), we see that the units they offer 5.3 GPM (These units produce 53,000 BTU heating output at 100% capacity) to 11 gpm (These units produce 199,000 BTU heating output at 100% capacity).

Let’s take the largest residential propane tankless heater as an example. That’s an 11 GPM Rinnai ru . Is199IP; This ‘199’ The model number tells you that this propane tankless heater produces 199,000 BTU/hr heating output when operating at 100% capacity.

How Much Propane Does a Rainai Tankless Water Heater Make?
This rinai RU . Is199IP; The largest is a 199,000 BTU residential propane-powered heater (the residential use limit is 200,000 BTU).

We know that such a unit would produce 199,000 BTU of heat output by burning propane. We also know that burning 1 gallon of propane will produce 91,452 BTU of heat.

From this we can calculate how much propane such a large tankless propane heater uses per hour. Here is the calculation:

Propane used in 1 hour = 199,000 BTU (heater capacity) / 91,452 BTU per gallon = 2.18 gallons of propane

This means that the largest propane tankless water heater will burn 2.18 gallons of propane per hour (at 100% output). We can also calculate how much it costs to run such a propane heater by multiplying the propane usage per hour and the cost of propane per gallon ($2.41 natural average). Here’s how we do it:

running cost per hour = 2.18 gal/h (propane use) × $2.41/gal (propane cost) = $5.25/h

You can do these calculations for pretty much any tankless propane water heater. Of course, we also need to keep in mind that propane doesn’t burn at 100% efficiency. The burning efficiency depends on the EF (efficiency factor) of the individual heater.

Now, this all might sound a bit complicated. So we simplified the whole thing with an easy-to-use propane usage calculator and a summary table at the bottom of the calculator.

You can use it freely here:

Tankless Propane Water Heater Usage Calculator

To calculate how much your tankless propane heater will burn in a year, you simply enter the unit size (in BTU), energy efficiency (this is usually around 95%), and how long you’re likely to be on per day. Keep unit use at 100% capacity.

This last one — the minute it runs per day — is what most homeowners struggle with the most. A standard household will use a tankless propane heater (at 100% capacity) for about 40 minutes per day.

Here is the calculator. You can also play with the numbers a bit:

As you can see, the amount of propane a tankless propane water heater can use depends on the size, efficiency, and how much you use it per day.

To make things even simpler, we’ve calculated some values ​​for the most common sizes of propane tankless heaters, and collected them in this table:

How Much Propane Do Different Tankless Propane Water Heaters Make Per Year (Table)

Here we use the average 95% efficiency for all calculations:

Size of Propane Tankless Unit (in BTU): Annual propane usage for 20 min/day: Annual propane usage for 40 min/day: Annual propane usage for 60 min/day:
53,000 BTU (5.3 GPM) 74.22 gallons/year 148.44 gallons/year 222.66 gallons/year
65,000 BTU (6.5 GPM) 91.03 gallons/year 182.05 gallons/year 273.08 gallons/year
75,000 BTU (7.5 GPM) 105.03 gallons/year 210.06 gallons/year 315.09 gallons/year
94,000 BTU (9.8 GPM) 131.64 gallons/year 263.28 gallons/year 394.92 gallons/year
100,000 BTU (10.2 gpm) 140.04 gallons/year 280.08 gallons/year 420.12 gallons/year
130,000 BTU (10.4 GPM) 182.05 gallons/year 364.11 gallons/year 546.16 gallons/year
160,000 BTU (10.7 GPM) 224.07 gallons/year 448.13 gallons/year 672.20 gallons/year
199,000 BTU (11 GPM) 278.68 gallons/year 557.36 gallons/year 836.04 gallons/year

Hopefully, you now have a better understanding of how much propane an on-demand propane water heater uses. Another useful article covers the topic of what size on-demand heater you need; You can check it out here.

If you have questions about your specific unit, you can use the comments for that and we’ll try to help.

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