Boiler vs. Water Heater: Which One is Right for Your Heating Needs?

Boilers and water heaters: they’re the same thing, right? After all, a boiler implies it’s boiling something, like water, so it could produce hot water for steamy showers and toasty wash water, right? Well, yes, but not always.

Key Points:

  • Boilers are multi-purpose heat sources that can be used for both providing hot water and heating your home.
  • Water heaters provide hot water but typically require a separate heating source for the home.
  • Boilers and water heaters use different methods of heating water/air – boilers use either oil, gas, or electricity, whereas tank-type water heaters use a gas burner or electric heating rod.

While boilers and water heaters are similar in that they both provide heat, there are a few key differences in what they heat. This article dives into the specifics of each option to help clarify the differences and why they’re both important, so continue reading to learn more!

What Is A Boiler?

Home Boiler System

Boilers are an essential appliance in many homes and function as a multi-purpose heat source. While the functionality of the boiler can vary based on the model in question, many boilers are capable of providing hot water and heating your home.

In most scenarios, boilers are used as residential space heating devices, pumping out heated air to ensure your home remains comfy and cozy throughout the chilly winter months. They’re similar to HVAC systems, like baseboard heaters, heat pumps, in-wall heaters, and modulating furnaces.

However, while they’re commonly known for their space-heating functions, they can also provide heated water for showering, washing dishes, running laundry, and more. Boilers that do both are commonly known as combi or combination boilers, as they can efficiently offer warmed air and hot water from a single unit.

How Do Boilers Work?

The inner workings of a boiler vary based on the model in question, but they all share similar workings. Since they require water to produce steam, the system usually features a water input valve on one end and an output valve on the other.

When the cool water enters the system, the boiler heats it using its heat source. The heat source depends on the model, but the source is usually oil, gas, or electricity. Once the water is hot, it produces steam, which the system pumps to radiators throughout your home. If your system provides hot water, it’ll pump the heated water through the plumbing in your home.

In many space-heating systems, the network is a closed loop, so the cooled water left over after the steam condenses travels back to the boiler. The boiler will reuse and reheat the water, sending it back throughout your home to continue heating it.

When used as a heating system for your home, the boiler will cycle as necessary to heat the space. It does this by communicating with a thermostat, which will trigger the heating cycle when the temperature dips below the set number. Once the temperature climbs to the correct set number, the thermostat tells the boiler to turn off.

What Is A Water Heater?

Bosch Thermotechnology 40-Gallon Tall Electric Storage Water Heater, Gray

A water heater is a standard appliance in most homes, acting as the sole hot water provider for various purposes. Water heaters come in a variety of shapes and sizes, including tank-type water heaters, which are the traditional type, and tankless water heaters, which are a more recent alternative to the traditional option. In addition, there are hot water recirculation pumps, indirect water heaters, and combi boilers.

Water heaters, as the name implies, solely provide hot water. Because of this, most homes integrate a separate heating source to keep the house warm and comfortable. While most homes have furnaces or heat pumps, there are other alternatives, like pellet or wood-burning stoves.

How Do Water Heaters Work?

Like boiler systems, the inner workings of a water heater can look drastically different depending on the model. For this explanation, we’ll focus on the two main types: tank-type water heaters and tankless water heaters.

Tank-type water heaters are the traditional option, featuring a large holding tank to store heated water. These systems have a cold water supply pipe feeding cool water into the system for heating. The system uses a gas burner or an electric heating rod to indirectly raise the temperature of water flowing into the tank.

Once the water is hot and reaches the correct temperature, the system transfers it to its storage tank, where it waits for use. Since these systems store a set amount of heated water (the tank’s capacity), you might notice the system will run out after a couple of people take lengthy showers. Once the holding tank is empty, it’ll take a while for the system to refill and provide ample hot water again.

Conversely, some homes have the more modern tankless alternative. These water heaters are entirely different than their tanked counterparts, as they don’t have a storage tank for the heated water. Instead, these systems heat water on demand. Once you turn on the hot water at a faucet or fixture in your home, the tankless water heater will automatically begin working to push hot water toward that fixture for as long as you have the water on.

Boilers vs. Water Heaters: The Differences

While similar in some aspects, boiler systems are quite different from water heaters. Here are a few of the most notable differences to offer clarity and help you decide which is better for your home:


The system function is the crucial difference between water heaters and boilers. While boilers can heat your home and your home’s water, water heaters are restricted to heating water.

So, while you could forego the heat pump or furnace if you have a boiler, you’ll need something like that to heat your home if you have a water heater. Water heaters don’t offer heating for your home, so you’ll need a heat pump, furnace, wood-burning stove, or something else that will keep your home warm and comfortable.


As many homeowners weigh the differences between boilers and water heaters, efficiency regularly comes up. After all, why wouldn’t you want the most efficient option? They help cut costs in the long run by providing better energy efficiency, making them more budget-friendly.

So, which one is more energy efficient, boilers or water heaters? Unfortunately, it’s not quite as simple as a yes or no answer. Efficiency ratings can vary drastically from one model to the next, so making a blanket statement is tricky, as it isn’t always true.

If you’re searching for the most energy-efficient option, we recommend paying attention to the AFUE ratings. The acronym, which stands for annual fuel use efficiency (AFUE), represents the system’s fuel consumption and indicates how efficient the system is. For example, if you see a model with a 95% AFUE rating, it means that 95% of its fuel source goes toward its function (heating water, heating your home, etc.), while 5% is lost.


More often than not, boilers are the pricier option of the duo. Most homeowners pay between $4,200 and $10,000 for a new boiler system, which averages around $7,100.

On the other hand, water heaters are much cheaper. Many homeowners pay between $500 and $1,500 for a new water heater or an average of $1,000. Of course, some models are pricier than others, so you might pay more for the system. For example, tankless water heaters tend to be more expensive than their tank-style counterparts.


The lifespan of each unit is another essential consideration, as you’ll want to get your money’s worth out of your investment. In most cases, boilers and water heaters offer similar lifespans.

For example, a standard gas boiler and a typical water heater have similar lifespans of 10 to 15 years. Of course, the unit’s lifespan hinges on its quality and care, as high-quality and well-maintained units usually last far longer than their low-quality or poorly-maintained comrades.


To ensure your boiler or water heater properly functions for many years. The required maintenance of each system varies, but both systems require routine maintenance to ensure everything is working correctly.

With boiler systems, regular maintenance usually includes the following:

  • Annual inspections to verify water levels remain within range and there aren’t any leaks
  • Complete flush and clean-out bi-annually
  • Routine cleaning of vents and flues
  • Descaling to remove lime buildup as necessary
  • Lubrication of moving parts bi-annually to ensure proper function

Conversely, routine maintenance for a water heater usually entails the following:

  • Routine inspections to look for leaks and other issues
  • Tank drainage and sediment removal to promote proper function
  • Regular water valve tests to ensure it regulates the water flow properly

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