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Top 10 Boilers of 2018

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Updated: Aug. 17, 2018

FurnaceCompare tracks more than 530 series of boilers. Of those sold in 2018, which are most highly rated by homeowners?

The list below represents the top-rated boilers available for sale in the US and Canada. These furnaces vary in efficiency from 81.3% to 95% efficient, as measured by the Annual Fuel Utilization Efficiency or AFUE. They also vary in features and price.

Rank Brand and Series Consumer Rating Efficiency (AFUE) Average Pricing
10. Buderus G215 3.4 out of 5 up to 86.3% $3,324
The Buderus G215 is an oil-fired cast iron boiler which uses a three-pass system design which heats the water three times. It features GL-180M gray cast iron, which according to the manufacturer provides 40% greater flexibility and reduces thermal shock due to rapid temperature change. There is a full 3" layer of insulation around the boiler, including the bottom, to help reduce standby losses and increase efficiency.
9. Peerless WBV/WV 3.6 out of 5 up to 87.5% $1,853
The Peerless WBV/WV is an Energy Star certified oil-fired boiler. The units are designed to be vented through a chimney, features cast iron construction, and can be used as part of either a hot water or steam system.
8. Buderus G115WS 3.67 out of 5 up to 87% $2,635
The Buderus G115WS is an oil-fired cast iron boiler, and it can be configured as a direct vent, or vented through a chimney. This Energy Star certified unit uses a 3-pass flue design to maximize efficiency.
7. Westinghouse Combi Boiler 3.69 out of 5 up to 95% $2,399
The Westinghouse Combi boiler is an environmentally friendly, low NOx system available in wall-mounted and floor-standing models. It is available in LP or natural gas and features a stainless steel heat exchanger with a fire tube design for optimal durability and efficiency. It also features a built-in gas leak detector which shuts off the unit and activates an alarm in the event of a gas leak.
6. Peerless MI 3.75 out of 5 up to 82.2% $2,470
The Peerless Series MI gas-fired, cast iron boiler is designed for natural draft use with a conventional chimney. It is available with spark ignition and features a low-profile design, allowing installation in areas with limited clearance. Other features include easily accessible controls, an electrically operated vent damper, and a boiler reset control with low water cut-off.
5. Triangle Tube Challenger Solo 3.8 out of 5 up to 94% $2,607
Triangle Tube's Challenger Solo is a wall mounted gas boiler with a copper tube / aluminum block heat exchanger. It can be vented with a variety of pipe material and size options, including a concentric venting option, and is indirect water heater compatible.
4. Slant/Fin Galaxy GXHA 3.86 out of 5 up to 81.3% $2,378
The Slant/Fin GXHA is a high performance gas-fired steam boiler with an intermittent pilot ignition and an optional tankless heater. It is built for installation in tight lcations with little headroom.
3. Bosch Greenstar 4.57 out of 5 95% $3,199
The Bosch Greenstar gas boiler uses a combustion process which achieves up to 95% efficiency and reduces nitrous oxide emissions. It is available as a heat-only or combination boiler and can be installed as a floor-standing or wall-mounted unit.
2. Slant/Fin Sentry 4.67 out of 5 up to 84.4% $1,932
Slant-Fin's Sentry is a gas-fired cast iron boiler available in five sizes. It features front-mounted controls for easy installation and maintenance, and an advanced natural draft design provides efficient operation and reliability.The Sentry's lower profile design makes it easy to install in sites with limited space or low chimney connections.
1. Lennox GWM-IE 4.75 out of 5 up to 95% not available
The Lennox GWM-IE is a gas modulating condensing boiler which the manufacturer states provides up to 40% greater efficiency than conventional boilers. Its modulating burner is designed to operate on a low setting most of the time, reducing sound levels and fuel costs while maintaining a precise temperature.


Consumers and homeowners have submitted thousands of reviews to this site. In addition to reviewing a particular model of equipment, the reviewer also assigns a rating from 1 ("Very Unsatisfied") to 5 ("Very Satisfied"). The following list ranks the top 5 boiler series from worst to best, based on the average of those consumer satisfaction ratings. has collected reviews on 74 different brands and 350 different series of boilers. However, we have only included a series on this list if we have at least 5 reviews of that series, and if the series is available in 2018. If we only have a few reviews, there is a risk that a single homeowner will skew the average rating too far in one direction or another.


The prices displayed are the average prices (of units including a burner) that we found on the websites of internet retailers that sell this particular series of boiler.

Note that prices -- even when they are published online -- can vary substantially based on the capacity of the unit in question: 24,000 BTU units are typically cheaper than 60,000 BTU units of the same brand and series.

Detailed Review of Boilers

1. Lennox GWM-IE

Earning the Energy Star Most Efficient 2015 Label, the Lennox GWM-IE is a wall-mounted, gas modulating condensing water boiler with an efficiency rating of up to 95% AFUE. Special innovative features found in the GWM-IE model include an economical electronic ignition switch that monitors temperature and prevents excessive use of the burner as well as a combustion tube designed for improved sound reduction. The heat exchanger tube is self-cleaning and the mesh burner is corrosion resistant.

The Lennox GWM-IE has a 15-year warranty on the heat exchanger and a 10-year warranty on the remaining covered components (labor costs are not covered by warranty)


  • Several reviewers praised the significant price drop on monthly energy bills
  • Several praised its efficiency of heating in the winter
  • Several praised the modulator which runs automatically


  • One reviewer complained that the unit required constant repairs and had ignition problems.
  • Expensive purchase price

2. Slant/Fin Sentry

The Slant/Fin Sentry boiler is a gas hot water boiler with an efficiency of 84.4% AFUE. The Sentry comes with several noteworthy features such a pre-purge option to conserve heat, a LED display which monitors system water temperature and allows the user to control the temperature as well, and a specially-designed insulated jacket to prevent heat loss and reduce operating noise.

The Slant/Fin Sentry Boiler comes with a 1-year warranty on parts and a lifetime warranty on the cast iron section, prorated after the 10th year.


  • Several owners praised the long lifespan of the boiler in comparison to other boilers on the market
  • Several reviewers mentioned that the boiler is quiet
  • Several owners stated that the purchase cost of the boiler is fair for the market.


  • One owner complained that the boiler takes a bit longer than normal to heat the house
  • One owner complained that it was bulky and took up too much space

3. Bosch Greenstar

Energy Star efficiency rated and with a 96.1% AFUE the Greenstar gas boiler offers a wall-hung model and can come as either a space heating boiler or a combi unit. The Greenstar includes features like an Al-Si heat exchanger and a fully modulating fan to increase efficiency. The unit comes with an LP and natural gas conversion kit.

Greenstar offers a lifetime heat exchanger warranty, prorated after the 10th year and a 5-year parts and labor warranty.


  • Several reviewers praised the efficiency of the boiler
  • Several owners mentioned how fast the boiler heats the house
  • Several owners praised the energy bills dropping in costs


  • One owner stated that the only problem is that after 10 years the fans need to be replaced

4. Slant/Fin Galaxy GXHA

The Slant/Fin Galaxy GXHA is a high-performance gas-fired steam boiler with an efficiency rating of 81.3% AFUE. The boiler features an intermittent pilot ignition, an optional tankless heater, and a monitor display to control system functions. The system also offers a specially-made speed skimmer trough that discharges contaminants and dirt through a drain faucet to reduce periodic cleaning time.

The Galaxy GXHA comes with a 10-year warranty on cast iron selection and 1-year warranty on parts


  • Several owners praised the speed in which the water was heated during winter
  • One reviewer noted that their energy bills dropped significantly


  • One reviewer mentioned a problem with turning on and off that required repair after only a few months.
  • Several owners mentioned that the cost of purchase was high compared to other brands on the market

5. Triangle Tube Challenger Solo

The Triangle Tube Challenger Solo is an energy efficient condensing boiler with an AFUE of up to 94%. The boiler is offered in four models ranging from 85 to 145 MBH. The Solo offers a digital control display with both U.S. And metric unit measurements, and an advanced modulating temperature control. The unit features a standard outdoor reset and has indirect water compatibility.

The Challenger Solo comes with a 1-year parts warranty and a limited 10-year non-prorated heat exchanger warranty. 5 and 10-year parts and labor warranty plans are also offered. Product registration for full warranty protection is required.


  • Several reviewers praised the boiler’s quiet operation
  • Several reviewers mentioned a significant energy bill cost savings.


  • One reviewer complained that the unit broke after only 3 years

6. Peerless MI

The Peerless MI series includes seven packaged hot water boilers offering up to 80.2% AFUE. Models in this series can be fueled by either natural gas or propane. The boilers are cast-iron and designed for natural draft chimneys. They feature a low-profile design for low-clearance installation. The MI series also offers features such as a flame rollout safety shutoff switch, a vent safety shut-off switch, and an option for either a standing pilot or an intermittent ignition. Standard Honeywell controls are included for facilitated maintenance.

MI offers a 1-year warranty on defective parts and workmanship on all cast iron boilers. The cast iron sections of the boiler carry a lifetime warranty covering defective parts and labor costs. Addition labor and parts coverage are offered for an extra fee.


  • Several owners praised the long life of the boilers
  • One owner noted that it was quiet


  • One owner complained that the boiler had a high purchase cost
  • Several owners complained that the boiler takes a little longer to heat the water than normal

7. Westinghouse Combi Boiler

The Westinghouse Combi is a modulating condensing gas boiler that combines space heating with an option for domestic hot water capabilities. There are two models, the combi floor model and the wall mounted model with AFUE efficiency up to 95%. The Combi Boiler features a stainless steel fire tube heat exchanger for higher efficiency and a ceramic fiber burner for high combustion and low NOx emissions. The Combi offers several safety features including a dual stage anti-freezing mechanism and a gas leak detector that turns off the unit and turns on an alarm in the case of a leak.

The Westinghouse Combi comes with a 10-year warranty on the heat exchanger and a 5-year parts warranty.


  • One reviewer praised the small amount of space occupied by the boiler
  • One reviewer appreciated the reduced carbon emissions


  • Several owners complained that the boiler does not function efficiently for a large family home
  • One reviewer complained that it is very noisy

8. Buderus G115Ws

The Buderus G115WS is an Energy Star labelled oil-fired cast iron boiler with an efficiency of 87% AFUE. It is constructed of flexible GL-180M cast iron which resists thermal shock during rapid temperature change. The unit features a 3” jacket around the unit to increase efficiency and lower heat loss due to standby in winter. It is designed with a front door and three access plugs to facilitate servicing the unit.

The Buderus G115WS comes with a 1-year parts warranty, a lifetime heat exchanger warranty that is prorated after the 10th year, and 5-year oil burner warranty. (Labor costs are not covered by the warranty).


  • Several owners praised the quiet operation
  • Several owners praised the heating efficiency of the boiler during winter


  • One reviewer complained of problems with the air intake part that was faulty and caused the furnace to stop functioning in high winds.

9. Peerless WBV/WV

Having earned the Energy Star Label and having an AFUE efficiency of 87.5%, the Peerless WBV/WV is an oil-fired boiler available for both hot water and steam systems. The boilers are offered in either fully-packaged or knockdown units. The cast-iron sections are assembled with steel push nipples. The boilers have an enameled steel jacket that reduces heat loss and a full-swing door for easy servicing.

The Peerless WBV/WV comes with a 1-year full warranty, a lifetime warranty on cast iron sections for residential boilers, and a 10-year warranty on cast iron sections for steam boilers. (labor costs are not covered by the warranty)


  • One reviewer praised the user interface.
  • Several reviewers mentioned that the boiler was very efficient.


  • One reviewer complained that Peerless was unwilling to cover boiler issues discovered at installation.
  • One reviewer complained of the noise from the boiler.

10. Buderus G215

The Buderus G215 is a cast iron oil-fired boiler with an efficiency of up to 86.7% AFUE. It is constructed to be flexible, corrosion-resistant, and designed to resist thermal shock. The unit is covered in 3” of thermal insulation to reduce heat loss. The boiler has a full-swing door for facilitated servicing.

The Buderus g215 comes with a 1-year parts warranty, a lifetime heat exchanger warranty, and a 5-year oil burner warranty.


  • Several owners praised the low energy consumption
  • Several owners stated that the boiler works perfectly after many years


  • One owner complained of a high purchase cost for the boiler
  • One owner complained that the boiler needs repairs every winter.

What Makes One Boiler More Efficient than Another Boiler?

For many homeowners who heat their homes with a residential boiler, the efficiency level can be a key factor in determining the best option. Within the home, boilers distribute heated water or steam through radiators or radiant floor systems. Many newer units have efficiency ratings of around 90%, while many older boilers have efficiency ratings as low as 50-70%. Though newer, high-efficiency boilers can reduce fuel costs, they also have some drawbacks which can include more expensive repair costs. Therefore, when evaluating a residential boiler’s efficiency, it is important to understand how the AFUE and the components of a boiler affect its efficiency and fuel usage.

How is efficiency measured (what is AFUE and how is it calculated)?

There are several ways to measure a boiler’s efficiency. AFUE stands for annual fuel utilization efficiency and measures the ability of the appliance to convert the fuel energy into heat. In other words, it is the measurement of heat output compared to fuel energy input over the course of a year. If a boiler has an AFUE of 90%, then 90% of its energy from fuel is converted into heat, while the remaining 10% escapes elsewhere. AFUE takes into account the performance of a boiler when it is operating at partial load or idling.

Mandated by the US Federal Trade Commission, new boilers must display their AFUE to make it easier for homeowners to compare efficiency rates. The Energy Independence and Security Act of 2007 requires that all residential gas-fired boilers and oil-fired boilers manufactured after September 1, 2012 have an efficiency of 82% and 84%, respectively. Following this mandate, in January 2016 the US Department of Energy enacted new standards for 2021 requiring 84% efficiency for gas-fired boilers and 87% for oil- fired boilers.

The Energy Star label is awarded by the US Environmental Protection Agency and Department of Energy to gas-fired boilers with an AFUE of 90% or higher and oil-fired burners with an AFUE of 87% or higher.

Another efficiency measure to consider -- particularly in regard to commercial boilers -- is combustion efficiency. Combustion efficiency is slightly different from AFUE and measures the heat lost up the stack when the boiler has been firing for enough time to reach an equilibrium. Unlike AFUE, combustion efficiency does not factor in jacket losses or off-cycle losses.

Before examining the different components of a boiler, it is helpful to know that higher efficiency boilers typically have electronic ignition to ignite the fuel, fans to control combustible air, and a condensing mechanism to save lost heat from flue gases. Lower efficiency boilers are typically older, use pilot lights to ignite fuel, and control the flow of combustible air using a natural draft design.

Pilot light vs electronic ignition

When selecting a boiler based on its efficiency, it is important to know whether your boiler has a pilot light or electronic ignition. Most new models have electronic ignition, while older, less efficient models have a pilot light. Furthermore, since September 1, 2012, newly manufactured gas-fired boilers are not allowed to have a continuously burning pilot light. Boilers with standing pilot ignition still use a pilot light that is lit 24/7 to ignite the main burners when desired. Pilot lights often need to be relit and can waste a small, but steady flow of fuel over time. Conversely, electronic ignition eliminates the need for a constant fuel supply because it is only used when heat is needed. Electronic ignition is more efficient than a pilot light, and it is a reliable method to ignite the main burners. Additionally, electronic ignition requires power to operate, while the thermopile and thermocouple provide power to the gas valve in a standing pilot light gas ignition system. Consequently, if there is a power outage, a boiler that relies on electronic ignition can lose power. However, this can be avoided with a backup battery or generator. Most new boilers are equipped with electronic ignition, and although these systems are much more efficient, they are also more complicated.

Natural draft vs fan controlled combustion air

Natural draft boilers have a specific burner assembly that naturally moves the combustion air upward without a fan. Once air from the surrounding room meets the point of combustion in the boiler, the air is heated and thus, has less mass than the surrounding ambient air. This temperature change pushes the combusted air upwards. Natural draft boilers also have natural-drafting chimneys that carry combustion gases out of the home. The height of the chimney and the buoyancy of the gases aid this process, but wind and chimney blockages can often prevent the gases from leaving. Improper venting and incorrect construction of the chimney can cause boiler failure, efficiency loss, or carbon monoxide leakage into the home. Exhaust fans can more precisely control the flow of combustion air and combustion gases than the natural draft system. Boilers with fan controlled combustion air are typically newer with mid to high-level efficiency. Old, low-efficiency boilers utilize natural draft flow.

Non-condensing vs condensing systems

Condensing technology is used in high-efficiency boilers with an AFUE of 90% or above. Boilers with these systems condense the water vapor in the flue gases to recover heat that would otherwise be lost from a non-condensing system when the gases exit the house. The gases exiting the flue of a condensing boiler typically have a temperature of 50-60°F, while the gases exiting the flue of a non-condensing boiler usually have a temperature of 120°. This discrepancy in temperature is an indication of the extra heat being extracted from the gases in a condensing system. Although these boilers are highly efficient, they can have larger upfront costs of sometimes double that of a mid-efficiency system. Therefore, it is important to calculate your payback from energy savings over time to ensure that the system makes up for the initial costs. Additionally, many high-efficiency boilers have higher repair costs and are more likely to need repairs because they have more complex computers and circuit boards. The payback from energy savings often takes around 10-15 years.

AFUE, ignition, air flow, and heat recovery are all important factors to consider when researching the efficiency of a boiler. High-efficiency boilers often have higher upfront costs and repairs, but they can reduce your energy bills. Older boilers tend to be less efficient and have entirely different components than the newer models. In any case, if you are installing a new boiler, it is important to research the contractor. Improper installation can also affect the efficiency of the boiler.

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