Boiler vs Water Heater – The Differences

When you turn on the hot water, use it for laundry, showering, dishes, or anything else, do you ever think about where the heat is coming from? Probably not. Most people never think about it until there’s a problem. 

But one thing is certain – you’ve heard the terms water heater and boiler, and your house probably has one of these two appliances. Do you know what are the differences between them? 

If not, keep reading, in this article, I’ll be comparing a boiler to a water heater in a couple of different departments so that you can be more informed about what you’ve got in your own house and/or which one of these appliances is best for you. 


What is a Boiler?

Radiator and water boiler

This appliance has been around for a very long time. It heats water in a way that’s very similar to that of the water heater. However, a boiler doesn’t use that water for faucets around one’s house, although some models can do that as well. 

Instead, the purpose of boilers is to send steam or water through the pipes that typically lead to things like floor heating systems or radiator heaters. In other words, their job is to heat homes with hot water or steam created by that very same hot water. Read more about different types of boilers.

What is a Water Heater?

Water heater in a kitchen

This is an aptly named appliance, as it does precisely what its name says. The main purpose of water heaters is to supply people’s homes with hot water. Every time you turn on a faucet, the hot water that comes through it is sent by your home’s water heater – it’s as simple as that. 

There are many different types of water heaters, but they all work in a very similar way. A vast majority of them do not perform other functions – they just provide hot water. Unlike the boiler, a water heater will not heat your house, only your water.

In case your water heater pilot light keeps going out, you will need to do something about it.

If you are also wondering what are the differences between furnaces and water heaters, check out my Furnace vs Water Heater comparison.

Boiler vs Water Heater – The Comparison 

In this part of the article, I’ll compare boilers and water heaters in four different categories – installation cost, energy efficiency, required maintenance, and typical lifespan. 

Installation Cost 

Man installing a water heater

“Which one of these two systems is cheaper to install?” is what most homeowners want to know first. The required amount of money to install either of these appliances depends on several different factors. However, I think it’s pretty safe to say that the boiler installation typically costs a lot more. 

A brand new boiler, along with the labor to install it, is bound to cost you somewhere between $3000 to $8000. When it comes to water heaters, on the other hand, one typically has to fork out somewhere between $1000 and $4000, and this includes both the appliance itself and its installation. 

Are you wondering whether you could save some money by handling the installation on your own? If that’s the case, I’d advise you against doing so, because that could easily cause you to void your warranty. Moreover, an experienced technician can do this in the safest way possible and according to local and state building codes. 

Energy Efficiency 

Gas bill

Which one of these systems is actually more efficient? First, we need to take a look at where these appliances get their power. Boilers, for example, can get their power from a variety of fuel sources, including heating oil, propane, natural gas, as well as some alternative fuel options. Water heaters, on the other hand, usually rely on propane, natural gas, and electricity. 

Due to the fact that energy efficiency varies from one model to another in both cases, it’s very hard to compare these two types of systems in this department. The efficiency of boilers is usually measured in yearly fuel use. The efficiency of water heaters, on the other hand, can be seen by looking at their energy factor. It tells one how much hot water a particular water heater can produce per unit of used fuel on a daily basis. 

Another important thing to mention here is that opting for a water heater means having to purchase and install a whole another system for house heating – as I’ve said, water heaters do exactly what their name says and nothing else. 

Required Maintenance 

Man repairing a gas boiler

It goes without saying, but both systems require a bit of maintenance here and there. However, I think it’s pretty safe to say that water heaters win in this department, as they’re less demanding than boilers when it comes to upkeep. 

Those who opt for a water heater will have to periodically check for leaks and test their valves in order to ensure that they can properly stop the flow of water. Draining the tank to remove the sediment buildups is yet another thing you’ll have to do from time to time. 

Boilers, on the other hand, require annual checkups of water levels, regular cleaning of vents, and periodical removal of lime buildups. You’ll have to fully clean out the system every six months or so, as well as lubricate the boiler’s moving parts at least twice a year. 

Typical Lifespan 

Old water heater parts

The typical lifespan of these systems is quite similar – standard water heaters and traditional gas boilers tend to last up to 15 years. 

No matter which appliance you ultimately decide to go with, you’ll want to choose a well-made model and maintain it as best as you can. Besides performing the DIY tasks I’ve mentioned above, you’ll also need to have your water heater or boiler serviced professionally whenever the need arises. 

If you’re really concerned with longevity, keep in mind that the tankless water heaters usually last the longest – when maintained properly, they can supply one’s home with hot water for at least 20 years, and sometimes even longer. The reason behind this is the fact that these systems typically consist of parts that are easily replaceable. 

Boiler vs Water Heater – The Conclusion 

While it’s true that both of these systems heat water, only one of them also provides heat for one’s home – the boiler (read my post on how to service an oil boiler as well). In other words, these appliances are similar but not interchangeable. For that matter, make sure to pick the right one for your needs.