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Boilers vs. Water Heaters: 7 Key Differences

Boiler vs Water Heater

Making sure you have enough hot water for showers, dishes, laundry, and other daily activities is important to keeping your home operational. Heating your home during cold winter months is equally important.

But which will do the job better, a boiler or water heater?

Let’s explore boilers versus water heaters, seven key differences between the two, and how to decide which is right for your home.

What is a Boiler?

While its name might suggest that it boils water, it does not. In fact, a boiler is a little more complicated than it may seem. Boilers work by turning water into steam, which is an efficient, inexpensive way to transfer heat throughout a home. Steam can easily be pumped through pipes since the gaseous form weighs much less than liquid water, and the gas holds heat better than air.

Boiler Installation

A boiler works by bringing cool water into the heating chamber where a gas burner heats the water. This transforms the water into steam, which is then pushed through the pipes in the home. Boilers can heat water very quickly and are usually tankless—though some may come with a tank and cylinder hot water storage system. 

While some boilers can and are designed to heat potable water, it’s important to note that not all boilers are. Most boilers are on a closed-loop system—meaning they don’t use new water when sending steam through the home but rather recycle water that’s been sent through the system already. Used water simply returns to the starting point to get reheated and reused.

This is one of the key differences to remember between boilers versus water heaters.

What is a Water Heater?

A hot water heater (unlike a boiler) does exactly as its name suggests: it heats water. This water can be used in your showers, sinks, laundry room, and more, since your hot water heater takes cold water from your clean supply line.

Once quickly warmed up and used, the water drains into your sewage system. Water heaters are designed to heat potable water that is safe for cleaning, cooking, and drinking.

Residential Water Heater

The two types of water heaters you’ll find today are tanked and tankless water heaters. In a tanked water heater system, the cold water coming in is warmed by a gas or electric burner system within the tank. Once the water has reached the desired temperature, it’s stored inside the tank until you use it from your sink or shower.

A tankless water heater works instantaneously rather than keeping a supply of heated water on hand. When you turn on a faucet to the “hot” side, a tankless hot water heater heats up water as it goes up to the appropriate faucet and keeps heating it until you turn off the faucet.

As you compare boilers versus hot water heaters, keep in mind that the latter doesn’t send steam through your home to heat it; it sends hot water directly to the desired locations.

What are the Differences Between a Boiler and a Water Heater?

Let’s explore the seven key differences between a boilers and water heater, including comparisons of efficiency, cost, lifespan, and more.

1. Types

When considering a boiler versus hot water heater, be sure you keep in mind the different types of each system. 

A boiler can come in two types: combination or conventional. A combination boiler (or a “combi” boiler) is a mix of a high-efficiency water heater and central heating boiler, all built into a single unit.

No type of water storage cylinder is needed with this unit. A conventional boiler works best within homes that already have a hot water heater system in place (for heating potable water) since it will likely be used to replace an older, already existing radiator system.

A hot water heater can also come in two types: tankless or conventional. As mentioned above, a tankless hot water heater doesn’t rely on hot water storage to heat your home’s water but rather heats the water as it’s required. A conventional hot water heater has a water storage tank and keeps hot water ready and waiting for when you need it.

2. Efficiency

It’s important to compare boiler and water heater efficiency when considering both systems. Most modern conventional boiler systems are capable of achieving efficiency ratings as high as 98 percent (which means they convert nearly all the energy used into heat for your home). Some older systems are in the 50-70 percent range. Most hot water heaters today have an Efficiency Factor of around 58-60 percent.

3. Cost

While the price of replacing a boiler or a hot water heater ranges pretty widely, there are some averages that can help you get an idea of what you’re dealing with.

Typically, a boiler replacement will cost anywhere from $4,000 to $7,500 and tends to include the removal of an old system and the installation of the new system. A new hot water heater can cost anywhere from $500 to $10,000 depending on the system you choose—though most are between $1,000 and $3,000.

Always be sure you work with a licensed professional when getting any plumbing work done, especially for something as important as a boiler or hot water heater installation. A bad installation job can end up costing you thousands in repairs or replacements down the road.

4. Water Storage

Most water heaters store hot water until it’s needed (unless it’s a tankless hot water heater) while boilers typically don’t store hot water at all. Most boilers heat water as it passes through the boiler system, which doesn’t require water storage.

5. Maintenance

Both boilers and hot water heaters require maintenance to remain operational. Since they both operate differently, however, they both require widely different maintenance jobs.

Water Heater Repair

A boiler’s vents and flues need to be kept clean. The water levels need to be monitored monthly (too little water can seriously damage your unit). The boiler needs to be inspected for leaks regularly.

All its moving parts require lubrication every six months. Any lime buildup needs to be descaled. The water needs to be flushed and replaced every six months.

For a hot water heater, the valve needs to be tested regularly to ensure it’s working properly. The anode rod must be checked and replaced if corroded. The drain tank needs to be kept clean. Pipes should be insulated to retain heat. The heater itself can be insulated to help keep stored water warm.

6. Lifespan

The average lifespan for a boiler is 15 to 20 years, though they should be properly maintained if you expect them to be around that long.

The average lifespan for a hot water heater is between 6 and 15 years. Again, well-maintained units are able to last much longer and units that are poorly maintained may quit on you early.

7. Versatility

Boilers can be used to heat the air of your home in forced air heating systems or floor radiating systems. They can be a fairly efficient way of heating your home and many homeowners enjoy the addition. Typically, boilers aren’t used to heat potable water in your home.

A hot water heater can be used to heat water wherever it is required: sinks, showers, dishwasher, laundry machine, etc. Hot water heaters aren’t usually used to heat the air in your home. 

How to Decide Which is Right For Your Home

When you really understand the difference between a boiler and a hot water heater, it should become much clearer which one you need for your home. While they both might sound like they do the same thing, a boiler is more like a furnace and is typically used in a radiator system to heat your home while a hot water heater is used to heat the water used in your home.

When trying to decide between a boiler versus a hot water heater, consider what you need most in your home and what system would best serve those needs.

Contact John C. Flood About Boilers and Water Heaters

Choosing between a boiler and a hot water heater for your home is complicated enough. Let us handle all the installation and repair work with our experienced and licensed team. John C. Flood can repair and install both boilers and water heaters, so reach out with any questions and schedule your service today.