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What Are the Types of Boiler Heating Systems?

Whether you are in the process of purchasing a new home, already own a home, or are looking to update your HVAC system, it’s important to understand your boiler options to maximize efficiency and be able to identify when something is wrong. 

As your best option for boiler installation in Walpole, Green Energy Mechanical Inc. has compiled a guide to the different types of boiler systems and an in-depth look at how they work. 

The Types of Boiler Heating Systems

There are three types of boilers:

  • Heat-only boiler: Also known as regular or conventional boilers, heat-only boilers are the most affordable. As the name suggests, heat-only boilers only provide heat, unlike combi and system boilers, which also provide hot water to the home. A heat-only boiler does not have a water tank.
  • Combi boiler: A combination boiler generates all the heat and hot water for the home within a single unit, so it does not require a separate water heater. These are the most space-efficient options.
  • System boiler: These boilers are similar to combi boilers in that one unit contains all the components like valves and pumps. However, they don’t generate their own hot water, so they require an unvented steel hot water tank in addition to the main boiler unit. These are the modern version of a heat-only boiler and are great for properties with high hot water demands since the tank can provide more consistent water pressure throughout the home. 

In addition to these three main boiler types, there is another boiler called a back boiler. These are somewhat antiquated boilers that some older homes have behind fireplaces. If you have a back boiler that needs replacing, you will need to install a wall-hung heat-only boiler somewhere else or consider a combi boiler.

How Does My Boiler System Generate Heat?

Now that you know what kind of boiler system you have, you’ll want to know how it generates heat. All boiler heating systems require a heat source to make them work.


Steam boilers use a heat exchanger to heat water and distribute it through pipes to radiators around the house. They work by utilizing pressure and gravity to push hot steam to radiators and cycle cooled condensation back into the boiler to reheat. All steam boilers have a pressure release valve.

Hot Water

Hot water boilers use a series of pumps to move hot water through your home. Your thermostat activates an oil or gas burner, which heats the water in the boiler, which then circulates through the system via pipes and radiators. Please note that hot water boilers are not the same as water heaters, which only provide hot water for showers, sinks, and other appliances.

Natural Gas

A natural gas boiler hooks up to a gas line that runs under the house via a pipeline from a nearby road. Homes in more rural locations use a propane tank outside the home as the fuel supply. The gas keeps a pilot light lit, which warms the heating coils in the boiler and heats the water in the tank. 


Considered to be highly efficient and eco-friendly options, electric boilers don’t burn any fossil fuels to heat the water in the boiler. Instead, your home’s electricity supply feeds electricity into the unit, which heats a metal element within the boiler, which heats the water. 


Oil boilers are water-based heating systems that use oil as fuel. In rural areas with limited access to natural gas, oil boilers are a more convenient option. A separate oil tank outside the home pumps domestic biodiesel into your boiler to heat the water and send hot water or air through the pipes in your home.


Condensing boilers utilize two heat exchangers: one to heat the water before it goes out to the radiators and another that reheats the water returning from the pipes in the home. Condensing boilers use the energy potential in exhaust flue gases to preheat the return water to the boiler. This method of extracting all available heat makes condensing boilers incredibly efficient

Contact Green Energy Mechanical Inc. For Boiler Maintenance Tips

You now have all the information you need to take great care of your boiler system! No matter what types of boilers you have, our team at Green Energy Mechanical Inc. can keep them running at their best, so contact us at 781-236-3421, and we’ll tell you when it’s time for maintenance or to flush your heating system before winter hits.


My furnace was not working this morning. I called Green Energy and within a few hours Terry was here and quickly took care of the problem. Terry has been here before and is very professional and friendly.
Ginny C.
Satisfied Customer
Very professional operation. Great technicians. Follow COVID protocol. Leave your house and property very clear with no trace that work had been done.
Susan G.
Satisfied Customer
Quinn was really nice, professional, and answered all my questions in a clear and easy manner. The woman I spoke with on the phone was also very kind, so I will definitely use this company again.
Peter T.
Satisfied Customer
Green Energy Mechanical is a pleasure to work. We had both air conditioning and heating installed. During both jobs, GEM was thorough and professional from start to finish.
Sussane P.
Satisfied Customer
I could not be more pleased with the service provided. We have upgraded our water heater to a tank less. We are also getting our heat and ac installed by them. They care for your home like you would
Bryan G.
Satisfied Customer

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