How do I know which size tankless water heater to buy?
Tankless heaters are sized based on the gallons per minute (GPM) they are able to produce. Each tankless heater has a GPM rating associated with it. The best way to size a heater is to determine the maximum flow rate that you’ll have at any time. You can assume that each shower requires 2.5 GPM. You may also need to consider any appliances that use a lot of water such as certain types of dishwashers or washing machines. The chart on this help section labeled Tankless Heater Selection will give you a better idea of which heater you need.
