What size of water heater do I need?
When installing a new hot water heater, it is important to choose the right size for your home and family. One that’s too big will increase your utility bills, but one that’s too small won’t provide enough hot water. Here’s how to determine what size hot water heater your family needs.
Storage Tank Water Heaters
Traditional storage water heaters need to hold enough water in their tank to meet your family’s peak demand. Every water heater has a first hour rating (FHR), which you can use to determine if a storage tank is large enough for your family.
To calculate your family’s desired FHR, first tally the number of people in your home. For most families, the number of bedrooms plus one is a good number to use for the number of people. For instance, a three-bedroom house would typically have a family size of four. Then, multiply this number by 12 gallons. That is the FHR. In the three-bedroom example that has four people, the FHR would be 48 gallons.
A hot water heater that has an FHR within a couple gallons of the number you just calculated should meet your family’s needs. You may want to adjust the figure, though, if you have a soaking tub or other special consideration. Typically this math breaks down so that families with:
- 1-2 people need a 30-gallon water heater
- 2-3 people need a 40-gallon water heater
- 3-4 people need a 40-50 gallon water heater
- 5 or more people need a 50-80 gallon water heater
Tankless Water Heaters
Tankless water heaters’ capacities aren’t measured in gallons stored but in flow rates. A tankless water heaters’ flow rate should be equal to your family’s peak demand.
To determine what size tankless water heater your family needs, list the water devices you expect to be used simultaneously. Then, add up the flow rates of each. The tankless water heater should have a flow rate equal to the number you arrive at. Many models have a maximum flow rate of 3.5 gallons, which is enough for a sink faucet and shower.
When in doubt, seek advice from your TLC Professional.