Boilers vs Water Heaters: What’s the Difference?

boilers vs water heaters: what's the difference

Some homeowners may be unclear on the difference between a boiler and a water heater. There is some crossover in the function boilers and water heaters perform, but these two appliances are not the same. Both appliances heat the water you and your family use, but boilers also provide heat for your home, while water heaters do not.

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We’ll explain the difference in more detail and discuss both of these home appliances so you understand what’s working behind the scenes to heat your water or, in the case of boilers, to heat your water and your home.

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What Is a Boiler?

what is a boiler

Let’s start by explaining what a boiler is and the purpose it serves. A boiler provides both hot water and heating for a commercial building or residential home. Focusing on the residential side, that means when you have a boiler, the hot water for your shower, your dishwasher, washing machine and more come from the same source that provides heat for your whole home.

That brings us to one of the major differences between a boiler and a water heater. With a water heater, you would need another means of heating your home, such as a furnace. A boiler not only heats water for use in appliances and showers throughout your home, but uses hot water to warm up your home whenever you turn on the heat during cold months.

Typically, the heat comes through either baseboard radiators or radiant floor systems. Though the name “boiler” suggests the water is boiling, most residential boilers do not get the water this hot.

Let’s take a look at some different types of boilers you’ll see on the market today.

High-Pressure vs. Low-Pressure

If you’re shopping for boilers, you may see a distinction between high-pressure and low-pressure units. There’s no need to make a decision here, however, if you’re choosing a boiler for your home. When it comes to residential heating applications, low-pressure units are standard. High-pressure units, which exceed 160 psig for water, are more common in commercial applications and require frequent monitoring, since they can cause safety issues.

Standard and Combination Setups

A standard boiler setup in a home will include a tank to store cold water and a cylinder for hot water. This setup has a pretty sizeable footprint, but it works well for large homes or households that use a lot of hot water, especially simultaneously.

Another option to consider is a combination boiler, commonly referred to as a “combi-boiler.” This type of boiler heats your home in the same way as a standard boiler, but rather than storing hot water for you to access through your home’s faucets and appliances, it heats water on demand when you need it. Eliminating the storage tanks means these boilers take up less space. You can think of combi-boilers as a similar option to tankless water heaters, which we’ll discuss more below. The difference is that, since they are boilers, they also heat your home.

What Is a Water Heater?

waterfall shower-head

We’ve talked about boilers and how they work, so let’s turn our attention now to water heaters. Water heaters, like boilers, provide hot water for use throughout your home, whenever you want to take a shower, wash your hands or run the dishwasher. Unlike boilers, this is the sole purpose of a water heater. Water heaters don’t play a role in heating your home.

Households that use water heaters instead of boilers have another means of heating the home. For most households in North America, this means is a furnace, though heat pumps are also common. Furnaces come in a variety of types and get their power from natural gas, electricity or fuel oil. Regardless of the fuel used, a furnace blows heated air through your home’s air ducts, and the warm air enters the rooms of your home through registers or grilles in a forced-air system.

When you have a furnace or another means of heating your home, you can depend on a water heater to provide hot water for your household. You’ll see two main types of water heaters on the market today — conventional storage water heaters, also called tank heaters, and on-demand, or tankless, models.

Tank Water Heaters

Standard water heaters are the most popular type of water heating system in homes. They include a tank that heats water and keeps it hot at all times, holding anywhere from 20 to 80 gallons. When you turn on your sink or shower, the hot water flows from your water heater, which typically lives in the basement, garage or a utility closet somewhere in your home, through the plumbing pipes to your faucet.

As hot water leaves the tank, it will begin to refill with cold water at the bottom. For many households, this system is sufficient to supply hot water whenever necessary. Some families, however, may occasionally use up the hot water at a faster rate than the tank can heat more. When this happens, you can temporarily exhaust your supply of hot water.

This phenomenon tends to occur when multiple people in the household are placing simultaneous demands on hot water. If you’ve ever been taking a shower while someone else was washing dishes or showering in another bathroom and noticed the water going from pleasantly hot to frigidly cold, you’ve experienced this limitation firsthand.

Tankless Water Heaters

Tankless, or on-demand, water heaters do not store hot water in a tank. Instead, they only heat water when you turn on a fixture or faucet that calls for it. Cold water runs through the tankless system, which takes up a fraction of the space of a standard tank model, and quickly gets heated as it passes through.

Because tankless water heaters heat water only on an as-needed basis, they tend to be more energy-efficient. They also can keep up with hot water demands more effectively in some cases. However, with an output between two and five gallons per minute, tankless water heaters have some limitations in how much hot water they can simultaneously provide.

Point-of-use units are a variation on tankless water heaters. Rather than one powerful unit that heats water for the whole house, point-of-use units are throughout a home, installed close to sinks or showers, so each unit can focus exclusively on providing instantaneous, uninterrupted supplies of hot water to those areas.


Comparing a Boiler and Water Heater

Besides looking at the ways boilers and water heaters compare in terms of what they do, we can also compare a few different aspects of these appliances, including their energy efficiency, installation cost, typical lifespan and required maintenance.


One thing some homeowners may want to know is whether a boiler or water heater is more efficient. To answer this question, let’s first look at where boilers and water heaters get their power. There are a variety of fuel sources for boilers, including natural gas, propane, heating oil and alternative fuel options. Typically, water heaters rely on electricity, natural gas or propane, though some models can run on solar power.

It’s challenging to make a direct comparison between boilers and water heaters when it comes to efficiency, since efficiency varies from model to model in both cases. Typically, manufacturers measure the efficiency of boilers in terms of annual fuel use efficiency, which tells you how much of the energy a boiler uses translates directly into heat. The standard measurement for the efficiency of water heaters is their energy factor, which tells you how much hot water the unit produces per unit of fuel consumed in a typical day.

It’s also significant to note that, with a water heater, you need another system for heating your home. If you’re concerned about directly comparing the amount of energy you would use in the case of a boiler vs. a water heater, you need to consider the additional energy consumed by a furnace or whatever heating system your home uses.

Installation Cost

Some homeowners also want to know, “Is a water heater or boiler cheaper to install?” The cost to install either of these systems depends on several factors, but generally, a boiler installation is a more significant investment. When we factor in the price of the unit itself as well as the labor to install it, a new boiler tends to cost somewhere in the range of $3,500 to $8,000.

When it comes to water heaters, installation costs, including the unit and the labor to install it, tends to be somewhere in the neighborhood of $1,000 to $3,500. Tankless water heater installations can cost more than other water heater options.

Some homeowners wonder whether they can save some money by purchasing the unit they want and handling the installation themselves. Whether you’re installing a boiler or a water heater, you should hire HVAC professionals to handle the installation. In some cases, you could void your warranty by trying to install your boiler or water heater yourself. When you hire licensed professionals to handle the job, you can rest assured they will set up the unit safely and according to state and local building codes.


comparing the lifespan of water heaters and boilers

When it comes to lifespan, boilers and water heaters are similar. Traditional gas boilers, as well as standard water heaters, tend to last 10 to 15 years.

If lifespan is your primary concern, you’ll want to choose a high-quality boiler or water heater and maintain it well. In addition to performing DIY maintenance tasks, have your boiler or water heater professionally serviced whenever necessary. Another thing to note for homeowners who are especially concerned with longevity is that tankless water heaters often have a longer lifespan. They tend to last upwards of 20 years if properly maintained. They can last an exceptionally long time, in part, because they consist of easily replaceable parts.

You don’t always need to wait until a water heater or boiler stops working to replace it. In some cases, you’ll want to replace your water heater or boiler even if it’s still functioning after a long time because better, more energy-efficient models are available.

Required Maintenance

Let’s take a moment to look at what maintenance tasks you’ll need to take care of with a boiler and with a water heater. Both these systems will require some maintenance, though water heaters tend to be a little lower-maintenance in comparison.

To maximize the life of a boiler, you’ll need to:

  • Inspect it annually to ensure water levels are where they should be and there are no leaks.
  • Regularly clean any vents and flues, and descale lime buildup as needed.
  • Fully flush and clean out the system every six months.
  • Lubricate any moving parts twice per year.

For water heaters, particularly ones with tanks, you’ll periodically need to:

  • Inspect your water heater to look for any leaks or other issues.
  • With the power off, test your water valve to make sure it stops the flow as it should.
  • Drain the tank and get rid of any sediment that has settled inside.

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Contact Home Climates for Boiler or Water Heater Maintenance and Installation Services

water heaters and boilers cta

If you live in the Central PA area and are looking to have a boiler or water heater installed, or if you need some professional maintenance performed on your current heating system, Home Climates can help. We’ll handle your heating system installation with the impressive level of skill and care our clients have come to expect from our team of technicians. We can even handle more complicated installs, such as a conversion from oil to gas.

When you want your boiler or water heater installed properly and serviced effectively, you can depend on Home Climates to get the job done right. We can also help answer any remaining questions you have about boiler and water heater options and what would be best for your situation. Contact Home Climates today to receive an estimate and get started.

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