So, you’ve decided that a tankless water heater or demand –type water heater is the best choice to replace your current, aging water heater. But, how do you know what size is best for your family?  It is important to get the proper size so your family will have the hot water they need, but you will not be paying for more appliance than you need.

To determine what size tankless water heater is best for your family, you will need to:

1.    Count all the devices that your family may use at the same time.
2.    Add the flow rates (the amount of water that flows through a device in one minute) of these devices together to get the number of gallons of water that the water heater will need to heat during that peak time.
3.     Know the number of degrees the water coming into the tankless water heater will need to be heated to. This is called the temperature rise.

To determine the flow rate of a particular appliance or device, consult the owner’s manual or you can look online for average rates for particular devices.

For most uses a good temperature of the hot water coming out of the faucet is 120 degrees. If your dishwasher does not have an internal heater, you may want your water heated to 140 degrees for the most efficient clean.

You will need to determine the temperature difference between the water coming into the tankless water heater and the temperature needed. For the Wichita area, the ground water temperature is approximately 57 degrees. Subtract 57 from 120 (the temperature of water wanted). That number is the temperature rise you need. In this case it is 63 degrees.
Usually a temperature rise of 70 degrees is possible at a flow rate of 5 gallons per minute for a gas unit and 2 gallons per minute is possible for an electric one.

For help in choosing and getting installation of the proper size tankless water heater contact Comfort Systems. We have been proudly serving the Wichita area since 1996.

Our goal is to help educate our customers in Wichita, Kansas about energy and home comfort issues (specific to HVAC systems). For more information about tankless water heaters and other HVAC topics, download our free Home Comfort Resource guide.