Learn how to choose the right size water heater, whether you need a tank or tankless model

Water heaters
are responsible for heating your home’s supply of water and immediately supplying that hot water to fixtures and appliances.

This guide will help you learn which size and type of water heater is best for your needs. It will also show you how to calculate the amount of water your family uses and how much space you need to allot for your water heater.

We highly recommend having your water heater installed by a professional as it is a difficult and sometimes dangerous process.

Note: Nationwide energy-efficiency regulations set in 2015 impact people buying new or replacing old hot water heaters. Your old water heater model number may not be the same as your new model number, so make sure to purchase based on capacity size instead of model number. Additionally, the size of all water heater tanks have increased, while the amount of water that they hold has decreased. Measure the space you have available for your water heater carefully so you can accurately judge what size water heater will fit. Learn more through Rheem’s National Appliance Energy Conservation Act guide.

Tank vs. Tankless

Choose between a traditional tank water heater or a smaller, eco-friendly tankless water heater.

Type How it Functions Factors to Consider

Conventional Tank

Stores constantly heated water

  • Economical
  • Can be positioned in closet, basement, or garage
  • Capacity ranges from 20 to 80 gallons
  • Efficiency varies between models, brands, and fuel sources


Heats cold water with a gas burner or electric element as it passes through the water heater

  • Require a larger up-front investment
  • Hang on wall and frees up floor space
  • Excellent option for residences occupied part-time
  • Reduce energy consumption by as much as 30%
  • Can run out of hot water during heavy usage
  • Require ventilation


Heats cold water via an electrical heating element and heat pump that pulls in ambient air and extracts the available heat

  • Require a larger up-front investment
  • Magnesium anode rod extends life of the tank
  • Heat pump delivers more hot water, up to 33 percent faster than standard electric water heater

Tank water heaters are traditional water heaters that work with gas and electric fuel sources. They offer a large volume of hot water that can be dispersed to your entire home. Tank water heaters typically keep the stored water at a temperature near 120 degrees Fahrenheit at all times.

water heaters
do not store heated water.  Instead they heat water  as it is needed. This can bring considerable savings.  They can work with gas and electric fuel sources.

It’s best to install tankless water heaters close to where they will be used, but they can service the whole house. They are popular as an eco-friendly alternative to traditional  water heaters.

If your family uses a lot of hot water, you might want to consider more than one tankless water heater.

Hybrid water heaters use advanced heat pump technology to pull in the ambient air and extract the heat to warm the water. They also service the whole house.

oint of use systems are individual units that install directly under the sink or in a closet. These systems deliver instant hot water to a specific location without wait time. Point of use systems typically augment a whole house system when instant or additional hot water is needed.