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Heating

The difference between a boiler and a water heater

Quick answer

A water heater heats water for your faucets, showers and appliances. A boiler heats water (or makes steam) that circulates through radiators or radiant floors to heat your home. Some homes use a combination boiler or an indirect tank so one appliance does both.

A boiler system serviced by Powell's

For some, a boiler and a water heater may seem to have the same functionality, they both heat water throughout the home. While this may be true of how they function, the two systems have very different purposes for heating water. It’s important to know the difference between the two so you know how to properly handle each.

  • What is a water heater?
    • It heats water that you use to shower, wash your hands, cook and clean with. It takes cold water and heats it up to pump it through your home when you turn the water on.
    • There are two types of water heaters, tanked heaters and tankless heaters.
      • Tanked heaters store the water in a tank and heat it as it moves through using either gas or electric.
      • Tankless heaters heat the water instantly for as long as you have the water running.
  • What is a boiler?
    • It turns water into steam as an inexpensive and efficient way to transport heat. It is used as a heating element rather than a water heating element, although it can heat pipes transporting water as it moves through the home.
    • They operate on a closed loop system, meaning they do not continually use new water but rather water that is inside the boiler. Once the steam cools, it turns back into water, and moves back into the boiler.
  • What’s the big difference?
    • Boilers are primarily used to heat the home through steam. Water heaters are used to heat water for cooking and cleaning.
  • How do I protect them?
    • MAINTENANCE. Both systems generally last around 10-15 years, sometimes 20 if they are well maintained.
    • Replace them in a timely manner. If your water heater is leaking or your boiler is experiencing corrosion, it’s time for a new one. Think ahead, don’t get caught in the middle of winter without your boiler. Have it replaced during the summer or early fall.

More tips from our team

  • Older boilers waste fuel. A modern high-efficiency boiler can use noticeably less fuel than one from decades ago.

Frequently asked questions

Can a boiler heat my water too? +

Yes. A combi boiler or an indirect water heater lets the boiler supply hot water as well as heat.

How long does a boiler last? +

Often 15 to 30 years with yearly service.

When should I replace my boiler? +

When repairs are frequent, efficiency is poor, parts are hard to find, or there are leaks or rust on the heat exchanger.

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