Difference Between Water Heater and Boiler (With Table)

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Water heaters are common residential appliances with the singular purpose of heating water to come out of household faucets. Boilers are residential or commercial systems that heat water for faucets, but also create hot water for area heating systems.

Difference Between Water Heater and Boiler: Overview

A water heater (called a geyser in some parts of the world) and a boiler can often be mixed up with one another as they both perform the function of heating water for the home. However, they are actually not the same thing.

A water heater heats fresh cold water in a large tank and then distributes it throughout the house for when hot water is needed.

A boiler also heats the water. Some of this is used as hot water from faucets. However, a boiler is also capable of heating water to the point that it turns into steam. This steam can heat up the house’s radiator thereby providing warmth to the entire home.

What is a Water Heater?

Purpose of Water Heaters

Water heaters are essential in every home, as they make life easier and warm up the cold days. When a water heater isn’t functioning efficiently, we definitely notice.

Water heaters make use of electricity or gas to heat water to a higher temperature, and often store this water so that it is available throughout the day. This hot water is used in the home for a variety of reasons. Whether it is to supply hot water for cleaning, bathing, or cooking, it is an essential part of daily life.

Stiebel Eltron 233219 2.5 gallon, 1300W, 120V SHC 2.5 Mini-Tank Electric Water Heater

General Operating Principles of Water Heaters

The basic function of a water heater is to heat water. However simple this may sound, the method is a bit more complex. It doesn’t really matter if the water heater is electric or gas-powered, they both work the same way.

Here are a few vital components of a water heater that will help illustrate the process.

  • Firstly, the water tank will heat and store the hot water. The tank comes in various sizes, but the average tank can hold 50 gallons of water.
  • The dip tube is the pipe where cold water from the main supply enters the water tank.
  • At the bottom of the tank, you will either find a gas burner or an electric heating element (depending on what type of water heater you have), which will heat the cold water.
  • The heat-out pipe expels the newly heated water from the tank and into the home.

Now for the process:

The water supply to your home will enter your mainline, and travel towards your water heater. The line splits into two: one for hot water and one for cold water. The hot water line will then run to your water heater.

Once someone turns on the hot water faucet, cold water will pass through the shut-off valve, run through the dip tube, and will enter the water heater.

At the bottom of the water heater, a heating mechanism will warm up the water to a specific temperature. Older water that was already heated will rise to the top, while newer cold water will remain at the bottom until it is heated. The hot water will travel through the heat-out pipe, and out of the faucet.

Types of Water Heaters

There are a handful of types of water heaters that are used in homes.

  • Conventional Storage water heaters are relatively common. These water heaters comprise of a tank, which stores hot water so that it is ready to use every day. However, this can become a problem when multiple people are using the hot water at the same time, as the hot water can quickly run out, meaning you will have to wait a while for the hot water to store up again.
  • Heat Pump water heaters are great energy and cost savers.
  • Tankless or demand-type water heaters are essentially the opposite of your conventional storage water heater. Instead of heating the water once and storing it in a tank, these water heaters will heat the water as and when it is needed, so you won’t need to wait for the hot water to store up.
  • Solar water heaters are another great cost saver as they use the sun’s energy to heat up the water, as opposed to gas or electricity.
  • Tankless coil and indirect water heaters will make use of the house’s heating system to heat up the water, as the cold water will flow through the house’s heating coils and come out hot out of the faucet.
Types of Water Heaters

What is a Boiler?

Purpose of Boilers

Boilers heat cold water to produce either hot water for daily use or steam for heating. They can be used both in homes or for commercial use as their function is essential for daily life.

The steam can be used to simply heat the water needed for cooking or showering, but it can also be used for heating the home as the steam can travel through the radiators to warm it up. Boilers can even heat the air in certain air heating systems, and the floors if you have a radiant heating system.

General Operating Principles of Boilers

Boilers are made up of a variety of parts that enable them to perform their function efficiently.

One important component is the superheater, which will intensely heat up the steam before it goes through the turbine. A feed pump will pump water into the boiler continuously as it heats up. The air preheater does exactly what its name suggests. It preheats the air in the boiler to increase its efficiency in producing steam.

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The way a boiler works is definitely more complicated than a water heater, but the exact mechanism depends on the type of boiler you have.

A gas boiler is connected to your house’s gas line. When turned on, the boiler ignites a flame, which will heat up this gas. The gas enables hot jets to heat up the water that runs through the boiler, and then a pump will expel the heated water through your pipes to your faucets, and through your radiator.

A steam boiler will heat water by combusting fuel. There are pipes in the boiler that get engulfed in flame once the combustion occurs. This will cause the water to turn into steam, and then the steam will run along to the radiators to heat your home.

Types of Boilers

  • Steam boilers make use of a heat exchanger, gravity, and pressure to warm up the water, turn it into steam and distribute it to the radiators by a collection of pipes that are attached to boiler.
  • Hot water boilers make use of temperature and pressure in a series of pumps to regulate and distribute heated water around the home.
  • Natural Gas boilers make use of natural gas from your home’s gas line, which keeps a light lit in the boiler, which in turn heats up the coils in the boiler that will heat up the water.
  • Electric boilers are a common choice as they are the more energy efficient than some of the other options. They use electricity to heat the coils necessary for the boiler to function.
  • Oil boilers are fueled by oil, but are actually water-based. In a separate tank, an oil mixture is pumped into the boiler in order to heat it.
Types of Boilers

Table of Differences Between Water Heaters and Boilers 200-250

Water HeatersBoilers
Ideal for smaller spacesIdeal for larger spaces
These systems heat water and then store the heated water in a tankDoes not store water, only heats water as needed
Water heaters are relatively simple systemsBoilers are more complex systems
The function and purpose of a water heater is to get hot water from a faucetThe purpose and function of a boiler is not only to get hot water from the faucet but also to heat the house, floor, and air
This system purely heats up water to a certain temperature This system heats up water to a high enough temperature to make steam
Water heaters are more commonly used in homesBoilers are less commonly used in homes
Water can take a little longer to heat up with a water heaterWater is heated more rapidly in a boiler
Can be fueled by electricity, gas, or solar powerCan be fueled by gas, electricity, or wooden pellets

Do You Need Both?

After reading most of this article, you might be asking yourself if it is necessary to have both a water heater AND a boiler.

If you have an efficient water heater, as well as another method to heat your home, such as through solar panels, heat pumps, or with electricity, then it really is not necessary to have a boiler as well. Your home’s essential needs are being carried out, so there is no need to add another system.

If you do not have a home heating system, then having a boiler could eradicate your need for one, as well as your need for a water heater because the boiler can heat up the water you need and provide heat to your home.

In short, if you have a boiler you do not need a water heater. However, if you have a water heater you might want to consider having a boiler if you do not have any other methods of heating your home already in place.

Should I Get a Water Heater or a Boiler?

The choice of whether you get a water heater or boiler will have a lot of considering factors. Determining which one is best, depends on your family’s overall needs and budget.

Difference between a boiler and heater regarding costs, function, durability, and maintenance


When it comes to deciding on whether you want a water heater or a boiler, the cost might influence your decision. A water heater is definitely the cheaper option compared to a boiler, coming in at around $3,000, including installation. Obviously, the larger the water heater you get, the more expensive you can expect it to be.

A boiler is definitely harder to install and a more complex system, so the total price ranges around $7,000.


If you decide to only get a water heater, you will be left with the task of making sure you have another system in place to heat the rest of your home, since a water heater only heats up the water that will come out of your faucet.

A boiler, on the other hand, will fulfill both the need for hot tap water as well as heating the floor, air, and rest of your house.


When you are assessing how long your boiler or water heater will last, the good news is that they both have a similar lifespan of 10 to 20 years if you keep up with regular maintenance and invest in high-quality systems.


The boiler requires a little more time and effort when it comes to maintenance in comparison to the water heater. You will need to flush out the system and lubricate the parts at least twice a year which can be a tedious and time-consuming process.









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