proper size tankless water heater

Choosing Proper Size for a Tankless Water Heater

If your home is in need of a new water heater in the near future, a modern upgrade you should be strongly considering is the tankless water heater. Also known as an on-demand water heater, the tankless water heater removes the traditional tank from the equation, instead providing hot water through an on-demand heating component that brings several distinct benefits, including major water savings and several convenience areas as well.

At Action Plumbing, Heating, Air & Electrical, we’re happy to offer the highest quality in tankless water heaters available today, plus experienced plumbers who will help with every area of water heater replacement. Perhaps the single most common question our plumbing contractors get when considering a tankless water heater for their home: What size unit should I be purchasing and installing to meet my home’s water needs? Here are the important factors that help determine the answer to this question.

Flow Rate Requirements

The first metric to be aware of is flow rate, which refers to the amount of hot water the tankless unit is able to produce. Flow rate is generally listed using gallons per minute (gpm), and your unit must have the requisite capacity to meet the needs of all your fixtures.

When you have the expected flow rate of the various fixtures in your home, you can use this information – combined with how often you expect given fixtures to be used during peak times – to determine the total flow rate the system needs to be able to handle. Keep in mind here that tankless water heaters generally restrict you to one or two simultaneous water activities. As a reference, here are the average flow rates found in low-flow plumbing fixtures:

  • Showerhead: 2.5 gpm
  • Bathroom faucet: 1.0 gpm
  • Tub faucet: 4.0 gpm
  • Kitchen faucet: 1.5 gpm
  • Washing machine: 2.0 gpm
  • Dishwasher: 1.5 gpm

Temperature Rise Factors

The other major factor to be aware of when sizing your new tankless water heater is the temperature rise, which describes the temperature of the water when entering the system compared to how hot you need it to be when it comes out of your fixture. This involves knowing the average groundwater temperature in your region, something our pros can inform you of. You need a unit capable of delivering a temperature rise within your basic range, which will help determine the size you choose.

Combination Listings

In most cases as you browse tankless water heater models, flow rate and temperature rise metrics will be listed as a combination. For instance, units will provide their flow rate based on the required temperature rise – the former will often change based on the latter. Both must be considered when sizing your tankless heater.

For more on choosing the proper size for a new tankless water heater, or to learn about any of our plumbing or HVAC services, speak to the staff at Action Plumbing, Heating, Air & Electrical today.