Boiler vs. Water Heater – Pros & Cons

Last Updated on December 11, 2021

Boiler vs water heaterOne thing that can confuse many homeowners is the difference between a boiler and a water heater. They are both responsible for hot water, so what exactly is the difference between the two, and when do we use each type?

The Boiler

noritz combination boiler

Combination Boiler                                                  Image Credit: Noritz NRCB199DV, Amazon

Let’s look at the boiler first since it is a more sophisticated device. The boiler has a bunch of copper tubes filled with water that sit over the furnace and heat very quickly. The primary function of the boiler is to heat the water to create steam. The steam rises through our heating pipes and heats our radiators that heat our home. Once the steam cools, it drips back down the pipes to the boiler to repeat the process.

Since the boiler is so good at heating water and accomplishes it so quickly, it’s only natural to devote a section of the boiler to supply hot water to the home. This portion of hat water is what many people are referring to when they talk about a boiler. There are a few types of hot water heating boilers available.

Conventional Boiler

A conventional boiler has a cold-water tank to feed the boiler and a hot water cylinder to store hot water for home use.

System Boiler

A system boiler has no cold-water tank but uses a cylinder to store hat water for home use.

Combination Boiler

Combination Boiler

Combination Boiler, Credit: Noritz, Amazon

A combination boiler has no tanks and heats water on demand.

The boiler can create very high-temperature water that may be desirable in some situations. This boiling water is mixed with cold water to create the hot water used by the home. It can be dangerously hot, though, and scald you if you’re not careful.

Besides scalding, there are other problems with using a boiler to create hot water for the home. Another downside is that they create a minimal amount of hot water at a time, and if you’ve used a boiler for hot water, you’re used to cold showers. Creating more hot water requires firing up the furnace to heat the water in the boiler, including the water used for the radiators, so it is not very efficient.

Heating water in this way also means you need to keep your furnace running all year long. Continually running the furnace will significantly increase the wear and tear on your entire heating system and cause you to replace your furnace and boiler as much as 65 percent sooner than you ordinarily would.

  • Fast heating
  • Extremely hot water
  • Wears out your furnace
  • The small supply of hot water often runs out
  • An inefficient way to heat water

The Water Heater

Tankless Water Heater, Image Credit: Electric ECOTOUCH, Amazon

A water heater is a stand-alone unit with the sole purpose of heating water for use in your home. There are several types of water heaters available, but the most common ones are conventional and tankless.


Conventional water heaters are probably the most easily recognizable because they are the most common. These are usually tall cylindrical devices that contain a large tank that holds the water for heating and storage. Water is heated using any one of several methods, but it’s usually gas or electricity. Cold water enters through the bottom of the tank, and hot water exits through the top.

You can buy conventional water heaters in almost any size to suit your needs. The tank can supply plenty of hot water for long showers and laundry, and several people can shower in a row without running out of hot water.

The downside to conventional water heaters is that they need to keep the water hot around the clock. Continuous heating can use a lot of energy. If the water heater is old or is a budget model, the insulation around the tank might be insufficient to keep the heat in, requiring even more energy to make up for what’s lost.


Another type of water heater becoming popular is the tankless water heater. Unlike conventional water heaters, you won’t find these in the basement. These water heaters are usually mounted close to where they will deliver the hot water and use highly efficient water heating devices to heat the water on demand.

Only a few years ago, tankless water heaters were only used in science fiction because there was no way to heat the water fast enough to make them a practical part of your home. The technology has arrived now, though, and tankless water heaters are more than capable of delivering hot water to your entire family.

Tankless water heaters are the best solution for water heating because they don’t require any special tanks to hold and store the hot water, there are no insulation issues or drain on your furnace. As the price of tankless water heaters comes down and technology improves further, we are very likely to see more tankless water heaters in homes around the neighborhood.

See the best: tankless water heaters of the year


No matter how you heat your water, these devices need routine maintenance to maximize their life. Constant flushing and inspecting, along with regular visits by a professional, will help make sure you get the best value for your money.


Hopefully, after reading this article, you better understand the difference between a boiler and a water heater. If you need to purchase something for your home, we recommend going with a water heater over a boiler if possible. Every aspect of the furnace and boiler is more expensive than a water heater and putting additional strain on your home’s primary source of heat doesn’t make sense unless it’s the only solution.

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