Learn how to choose the right size water heater and 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.
Safety: We highly recommend having your water heater installed by a professional as it is a difficult and sometimes dangerous process. The Home Depot carries a vast selection of water heaters with the latest technologies and offers same-day installation.
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
How it Functions
Factors to Consider
Stores constantly heated water
- 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
- Requires a larger upfront investment
- Hangs 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
- Requires ventilation
Heats cold water via an electrical heating element and heat pump that pulls in ambient air and extracts the available heat
- Requires a larger upfront investment
- Magnesium anode rod extends life of the tank
- Heat pump delivers more hot water up to 33% faster than standard electric water heater
These do not store heated water. Instead, they only heat water as needed. They also work with gas and electric fuel sources. While they should be installed close to their most common point of use, they can service the whole house. Their temperature can be adjusted as often as desired, and they are popular for being eco-friendly alternatives to traditional tank water heaters. Depending upon your family’s water usage, you may need more than one tankless water heater.
Point of Use
Point 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.
How to Choose a Water Heater
First, identify your fuel type: natural gas, propane or electric. Then decide if you’d prefer tank or tankless. Next, use the calculations below to determine the size you need.
Tank Water Heaters
Determine your required gallon capacity based on the number of people who will regularly be using hot water in your home.
5 or more
56 or higher
Note: Your new water heater will likely be larger than your old one due to 2015 regulations requiring more insulation around the water tank. If you find you’ve run out of space in your current water heater cabinet, instead of relocating your unit, ask a Home Depot associate about non-standard sizes, such as a “low boy” model, which is shorter and wider.
1. Calculate how much hot water you need at any time.
Use this chart to calculate the gallons per minute (GPM) of hot water each of your fixtures and appliances needs and add up these amounts to get a total GPM for your household. For example, if you typically have one shower running, plus a dishwasher, and the clothes washer, you have a flow rate of 3.5-7.5 GPM.
Typical Flow Rates
0.5 - 1.5 GPM
3.0 - 7.0 GPM
1.0 - 2.0 GPM
1.0 - 2.5 GPM
1.5 - 3.0 GPM
2. Determine your home’s required temperature rise
Calculate the difference between your ground water temperature and your desired hot water temperature – typically around 120 degrees Fahrenheit. This is your required temperature rise.
For example, if you live in Atlanta, you have a ground water temperature of 62 degrees Fahrenheit. To reach an ideal hot water temperature of 120 degrees Fahrenheit, subtract 62 from 120. You have a required temperature rise of 58 degrees Fahrenheit.
Use the EPA’s map for average groundwater temperature for guidance.
3. Pick your water heater unit
Use your GPM and required temperature rise to determine which units will meet your needs. Each product information page on The Home Depot website includes this information, as do labels on the units in stores. Home Depot associates will be happy to answer questions about your purchase, or you can contact our Installation Services team at 855-400-2552 for help and installation.
Energy Efficiency & Installation Tips
Look for the Uniform Energy Factor (UEF) rating.
Most water heaters offer increased efficiencies to meet federal standards. The UEF rating measures how efficiently a unit converts energy into heat as well as how much heat is lost during storage.
Hybrid and tankless electric water heaters tend to have the highest UEF ratings.
Tankless Water Heater Installation Tips
- Be sure the location you choose for installation meets ventilation requirements. This is imperative for a successful installation.
- The ideal location is on an exterior wall near a gas supply line, water supply line and electrical power source. This is also the easiest and most cost-effective way to run the venting.
Tank Water Heater Installation Tips
- We urge you to consider professional installation for tank water heaters for your safety.
The unit should have ½-inch clearance on the sides, 12 inches on the front and 18 inches off the floor.
- Hybrids offer a narrow 21-inch diameter for access into smaller locations.
Money Saving Options
Many state and federal rebates are available for residential water heater purchases. These options will vary based on the city or municipality in which you live. Often available for ENERGY STAR® products, these rebates allow homeowners to purchase higher-end units at lower prices.
The Home Depot offers everyday savings on the best energy-efficient water heaters, and our trusted service providers can provide more information as well as explain our credit options. Contact us today at 800-HOME-DEPOT for your free consultation.
To extend your water heater’s labor warranty, sign up for The Home Depot’s Purchase Protection Plan. It offers leak protection from day one, 24/7 service and free removal and replacement for water heater tanks. Read the FAQ about our Water Heater Plans for full details.