Water Heater Buying Guide

In 2018, Consumer Reports tested multiple electric and gas water heaters, including traditional models with tanks and tankless units. While we found that these water heaters varied by type, individual models of the same style didn’t vary much in performance. Here’s how they compared in terms of energy efficiency and cost to operate.

Electric tanked water heaters received midrange scores on energy efficiency and low-level scores for energy consumption costs, meaning they cost more than many other types of water heaters to operate.

Electric tankless water heaters got very good scores for energy efficiency, and low scores for energy consumption costs. 

Gas tanked water heaters received midrange efficiency scores and very good energy consumption cost scores. That’s in part because natural gas tends to be an inexpensive fuel.

Gas tankless water heaters received very good scores for efficiency and excellent scores for energy consumption costs.

More recently, we tested 10 electric heat pump water heaters. Our tests found these units to be extremely efficient as a group. And there are also significant differences between models. See our ratings of heat pump water heaters.

To determine the size of the water heater you need, you’ll have to think about how much hot water you use. 

Tank water heaters typically hold 40, 50, or 55 gallons or more. The size you buy depends on the number of people living in your home and your peak water usage. A family of four, for instance, might take several showers, run the dishwasher, and wash a load or two of laundry in a day, possibly using 100 gallons of hot water or more. But that doesn’t mean that a household needs a 100-gallon storage tank, since water heaters operate continuously to produce more hot water over time.

For storage tank water heaters, it’s important to consider the first-hour rating, which is the number of gallons a water heater can deliver in an hour starting with a full tank of hot water. You can find this rating on the water heater’s EnergyGuide label. To calculate what first-hour rating might work for your home, use the calculator on the government’s Energy Saver website.

And if you’re sizing up your tank—or even swapping out the same size—don’t assume that a new water heater will fit where your old one was. Because of increased insulation and other efficiency improvements, some newer models may be wider and/or taller than your old water heater.

Tankless water heaters, of course, don’t store a reserve of water, so the number to look for when thinking about your hot water needs is the gallons-per-minute rating (GPM). That’s the number that tells you how much hot water the heater can deliver over a set period of time. The higher the GPM, the more hot water the unit can deliver. If you have a big family and multiple bathrooms, you’ll need a tankless water heater with a higher GPM. A typical shower, for example, uses about 2 gallons per minute. Front-loading washing machines use about 10 gallons of water per load, while agitator top-loading washers may use about 20 gallons. Calculate your needs accordingly.

Uniform Energy Factor (UEF): The UEF is the Department of Energy’s measurement for how energy-efficient a water heater is, and it was created to let consumers compare efficiency between models. The higher the UEF, the more efficient the water heater. You can find the UEF of Energy Star certified heaters on Energy Star’s website and of other models in their manufacturer’s specifications. But the Department of Energy cautions people against choosing a water heater based solely on the UEF, since factors like first-hour rating and overall cost are also important. 

Warranty: Coverage for water heaters typically runs three to 15 years. Though you’ll usually pay a bit more for models with longer warranties, we’ve found that they tend to have larger elements or burners that can speed up water heating, have thicker insulation for lower heat loss, thicker tank walls, and larger sacrificial anodes. Choose a water heater with the longest warranty available.

Mixing valve: A mixing or blending valve can help you increase your hot water capacity. If you find that your water heater often doesn’t meet your hot water demand, you can increase the temperature of the water in the storage tank. The mixing valve blends cold water with the very hot water to deliver the usual, desired temperature to the tap, effectively increasing the amount of hot water available. A mixing valve can be a good option if a smaller hot water tank fits your day-to-day purposes (or if you physically need a smaller tank for your space), but you want more hot water for visitors or when kids come home from college. 

Brass vs. plastic drain valves: These are specific to water heaters with storage tanks. The valves are situated near the base of the tank for a garden hose that drains the heater. Look for brass drain valves, which are more durable than plastic.

Glass-lined tanks: They’re designed to reduce corrosion in a water heater’s storage tank.

Digital displays and WiFi connectivity: Yes, there’s very likely an app for your water heater now, which enables homeowners to track energy use and access program controls, such as vacation modes to reduce costs. Displays on solar water heaters often show tank and collector temperatures, along with pressure readings and other info.

Yes, water heaters require some routine maintenance, which would be outlined by the manufacturer, though some types may need more attention than others. Whatever the requirements, a little regular TLC can extend your water heater’s life and make sure it’s working as efficiently as possible. 

For instance, nearly all hot water heaters have a pressure relief valve (a valve that prevents excess pressure from building up) that should be checked annually. A yearly check of all gas and water pipes for leaks is prudent, too. 

If you have a storage water heater, maintenance may include flushing a quart of water from the tank every few months, checking the temperature and pressure valves every six months, and inspecting the anode rod (meant to protect the tank from corrosion) every few years. 

If you have hard water, you may want to install a water softener to reduce hard minerals that build up. And some brands advertise anti-scale devices, which are supposed to reduce the buildup of mineral scale at the bottom of the tank by swirling the water. 

Maintenance for an on-demand (tankless) water heater might include cleaning the filter monthly or periodically descaling the heat exchanger tubes. For solar water heaters, you’ll want to do yearly checks for shading—think new vegetation or construction—to make sure nothing is blocking your solar collectors. You’ll also need to replace any heat transfer fluids periodically. 

But you don’t need anything fancy to ensure your water heater is cared for and working properly. Just read the owner’s manual and make sure you understand the instructions and potential costs of maintaining—or even repairing—your water heater over its lifespan.

Consumer Reports tests heat pump water heaters. To come up with our ratings, we test all models in heat pump mode only (even if they have the option to operate in “hybrid” mode, using electric resistance heating). We fill each water heater tank with cold water of the same temperature and then set them to reach a desired temperature of 120°F. We measure how long it takes for each model to reach 120°F, along with how much energy each model uses by measuring the wattage.