Quick Answer
Fuel consumption for a propane water heater is typically measured in BTUs (British Thermal Units) per hour. To calculate it, you need to know the heater's power output, usually expressed as BTUs per hour, and the desired flow rate of water in gallons per minute (GPM).
Calculating BTU Requirements
To calculate the required BTU output of your propane water heater, you need to know the desired flow rate in GPM and the desired temperature rise. Most water heaters have a temperature rise between 10°F and 30°F. For example, if you want a flow rate of 4 GPM at a 20°F temperature rise, your required BTU output would be 4 GPM x 10,000 BTUs/GPM = 40,000 BTUs per hour.
Choosing the Right Propane Water Heater
When selecting a propane water heater, you need to consider the maximum BTU output, the flow rate, and the required venting size. For a tankless water heater, the venting size is typically determined by the BTU output, the heater’s efficiency, and the local building codes. For example, a propane water heater with a 40,000 BTU output might require a venting pipe with a diameter of 3.5 inches.
Freeze Protection and Demand Requirements
To prevent freeze damage to your propane water heater in cold climates, you may need to install a freeze protection kit, which can include a heating element, a thermostat, and a controller. Additionally, you should consider the demand requirements for your propane water heater, which include the peak demand for hot water, the off-peak demand, and the duration of the demand. This will help you determine the required propane tank size and the number of propane tanks needed to meet the demand.
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