Written on: August 1, 2022
Have you been thinking about upgrading your old storage tank water heater to a durable, highly efficient propane tankless water heater?
One question that always comes up is: how much propane does a propane tankless water heater use? The short answer to that question is that a propane tankless water heater producing 40,000 BTU/hour will consume about 1.5 gallons of propane per day.
But let’s dig a lot deeper to gain a better understanding of propane tankless water heaters and, along the way, see how tankless water heaters compare with other common propane appliances in terms of fuel consumption.
According to the U.S. Energy Information Administration, a British thermal unit (Btu) is a measure of the heat content of fuels or energy sources. It’s measured by the quantity of heat that’s required to raise the temperature of one pound of water by one degree Fahrenheit–at the temperature in which water has its greatest density (approximately 39 degrees Fahrenheit).
Because BTU tells us how much heat energy is in a gallon of propane– one gallon of propane equals 91,452 Btus–we can make estimates about how much the average homeowner will use.
But keep in mind that the amount of propane your own appliances will use—including your propane tankless water heater– depends on factors ranging from the size and efficiency of each appliance to how well it was matched to your space, as well as the quality of the installation and the frequency of maintenance.
To make sure a tankless water heater will be able to meet your household’s needs, your propane service contractor will need to calculate these factors:
| Fixture | Average Flow Rate/ Gallons Per Minute (GPM) |
 Tub | 4.0 |
 Shower | 2.5-3.0 |
 Washing Machine | 2.0 |
 Dishwasher | 1.5 |
 Kitchen sink | 1.5 |
Learn more about flow rate here.
Prices range from about $170 for small gas-fired units to more than $2,000 for high-output heaters that can supply two showers at the same time; on average, the cost is about $1,000 per unit.
But keep in mind that propane gas-burning tankless water heaters should operate for 20 years or more. That’s two or three times longer than most storage tank water heaters as well as electric tankless water heaters.
If you experience an average energy savings of $150 per year, these savings should pay for your investment in a tankless water heater in about six or seven years. After that, you can pocket all of the savings on heating the water in your home.
With tankless water heaters on average using 1.5 gallons of propane per day, you may be wondering how your other propane appliances compare. The following estimates below should give you some idea of how much each propane appliance typically uses to do its job.
Please note that these appliance measurements are expressed as BTU per hour. This is a way to represent a measurement of deliverable power applicable to each propane gas appliance. (Think of it like the horsepower rating of a car). As an example, a typical furnace is about 100,000 BTU per hour. You can go here to read more about BTU per hour.
You can read more about propane tankless water heaters by going here. After that, reach out to your local propane service company for good advice.