Tank vs. Tankless Water Heaters

When a water heater fails, many homeowners face a choice they have not thought about in years: replace it with another tank, or switch to a tankless unit. Both can supply a home with reliable hot water, but they work differently and suit different households. Here is how they compare.

How each type works

Tank water heaters store a set volume of water and keep it heated around the clock. When you use hot water, cold water refills the tank and gets heated. Tanks run on gas, electricity, or as heat pump units.

Tankless water heaters, also called on-demand heaters, heat water only as it flows through the unit. There is no storage tank. They also come in gas and electric versions.

Upfront cost and installation

Tank water heaters generally cost less to buy and install, especially when you replace a tank with a similar tank. The plumbing and venting are usually already in place.

Tankless units tend to cost more upfront. Switching from a tank to tankless can involve extra work, such as:

• Upgrading the gas line to handle higher demand
• Installing new venting for gas models
• Adding electrical capacity for electric models
• Mounting the unit on a wall and rerouting plumbing

A plumber can tell you what your home would need before you commit.

Hot water supply

A tank can run out. Once you use up the stored hot water, you wait while the tank reheats. Larger households with several showers in a row may notice this.

A tankless unit does not run out in the same way, but it has a limit on how much hot water it can produce at once. If you run several showers and the dishwasher at the same time, a unit that is too small may not keep up. Proper sizing is important.

Energy use

Tank heaters lose some heat while water sits in storage, known as standby loss. Tankless units avoid that because they only heat on demand, which can make them more efficient for many households.

Actual savings depend on your hot water habits, fuel type, local energy prices, and the specific models you compare. Check the efficiency ratings on the products you are considering.

Lifespan, maintenance, and space

Tankless units are often designed to last longer than traditional tanks, though lifespan depends on water quality, maintenance, and usage.

Maintenance differs too:

Tank maintenance - Flush the tank to remove sediment, following the manufacturer's guidance - Check the anode rod periodically - Test the temperature and pressure relief valve

Tankless maintenance - Descale or flush the heat exchanger, especially with hard water - Clean inlet filters - Follow the manufacturer's service schedule

Skipping maintenance on either type can shorten its life and may affect warranty coverage.

If your home has hard water, a water softener or scale filter can help either type last longer. Ask your installer whether one makes sense for your area.

Tanks take up floor space in a garage, basement, or closet. Tankless units mount on a wall and free up room, which can matter in smaller homes.

Which one fits your home

A tank may be the better choice if:

• You want the lowest upfront cost
• Your current setup makes a like-for-like replacement easy
• Your household's hot water use is moderate

A tankless unit may be the better choice if:

• You want to save floor space
• You plan to stay in the home long enough to benefit from the longer expected life
• Your home can support the gas or electrical requirements without major upgrades

Warranty and home warranty coverage

New water heaters typically come with a manufacturer warranty that covers certain parts for a set period. Read the terms, since tank and labor coverage often differ.

Many home warranty plans cover water heaters, including tank and some tankless models. Check the contract for caps, exclusions for sediment damage, and whether code upgrades are paid during replacement. Our plumbing coverage page explains related coverage.

How Warranty Wizards can help

We help homeowners compare plans from independent third-party providers and explain how each one covers water heaters before you buy. You can request a free quote at /get-a-quote/.