7 Best Condensing Boilers | Boiler Prices, Pros & Cons, Reviews

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Most Homeowners Spent Between: Most People Spent: $6,960 - $10,370
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If it is time to replace your old boiler or perhaps purchase one for your new house, then it is worth having a look at the most efficient type available on the market – a condensing boiler. This type of boiler offers significant savings over conventional types and is more environmentally friendly. Together with installation, a condensing high efficiency boiler costs an average of $5,500-10,000.

We will discuss how a condensing boiler works, its benefits, associated costs, and 7 models that are most recommended.

Get in touch with your local plumber to get free price quotes to install a new boiler

Condensing boiler working principle

A condensing boiler, for the most part, works in the same way as a conventional boiler: the fuel is burnt to produce hot air which heats up the water via a heat exchanger. This heated water then circulates around the house through pipes, radiators or coils which transfer the heat to the surrounding air.

The only difference is that a condensing boiler has an additional heat exchanger that extracts extra energy from the flue gases, making it much more efficient than a conventional boiler.

The flue gases produced as a result of fuel combustion can be as hot as 480-570°F and contain water vapor which has a high energy content. In conventional boilers, the water vapor is exhausted into the atmosphere, but condensing boilers are designed to recover the latent heat from the vapor by condensing it.

They do it with the help of the second heat exchanger in which flue gases are cooled by the return water from the heating circuit. For condensation to happen, the return water temperature must be at or below the dew point temperature of the flue gases, which is around 131°F.

How a condensing boiler works

(Simple diagram of how a condensing boiler works)

As the return heating water cools down the flue gases and picks up the latent heat, its temperature rises. The water then flows through the main heat exchanger and requires less energy to achieve the design hot water supply temperature. This ensures condensing boiler efficiencies as high as 98%.

Did you know? Condensing boilers require a drain pipe to discharge generated condensate liquid. This liquid is only mildly acidic (typically pH of 2 to 4) and does not pose any threat to human, however, it can corrode the material of the pipe which is used to drain the condensate. In addition, some national and state codes prohibit anyone from discharging acidic liquid into the sewer system.

Pro Tip: Use non-corrosive pipes, such as PVC or ABS, to drain the condensate liquid from your condensing boiler. It is good practice to run condensate pipework in the area where a leak will not cause much property damage.

Also ask your contractor to check with the local authorities if it is allowed to discharge the condensate from your boiler into the public sewer. In case the acidity level is too low, a condensate neutralizer can be installed, which is usually a compact inline module filled with alkaline limestone chips.
Alternatively, the condensate can be drained into the limestone chipping soak-away. The neutralizer will also be required if there is an on-site septic system which can be damaged over time if the condensate is not treated.

Will a condensing boiler last for many years?

As a rule of thumb, a properly installed condensing boiler should have a service life of at least 12-15 years. Most condensing boilers last about 20 years.

To ensure that your boiler functions properly and does require replacement before the end of its service life, make sure to do very simple preventative maintenance. Your installer can tell you more specific details about when and how your new boiler should be serviced.

However, you can periodically do things like:

– check and clean the condensate trap and drain system.

– check and clean your boiler’s combustion chamber.

How much does a condensing boiler cost?

Forced Hot Water Boiler Costs
Gas Boiler
$3900 - $5600
Oil Boiler
$4800 - $6700
Base Boards
$2100 - $3500

See costs in your area Start Here - Enter Your Zip Code

The average cost to install or replace a condensing boiler unit starts at $2,500 and can reach as much as $11,000 depending on the model you choose and scope of work involved in the installation. Most homeoweners spend $4,500 – 8,000 to install a condensing or a combi boiler.

The price for the boiler itself can be as low as $1,485 and can reach $8,750 for a high-end Bosch Buderus SSB model with over 96% efficiency rating. Most condensing boilers fall in the range of $2,500-5,000 depending on the brand, efficiency rating, and capacity

The main factors that affect boiler pricing are as follows:

Boiler Function. As discussed earlier in this article, condensing boilers can be regular (providing heating only) and combi (providing heating and domestic hot water). Since combi boilers fullfill more functions, their cost is typically 10%-20% higher than heating only boilers.

Boiler Capacity. The price rises with the higher boiler capacity. Residential boilers will generally have capacities in the range of 35 MBH to 399 MBH.

Boiler Efficiency. The higher the efficiency the boiler can reach, the more expensive it will be. Most condensing boilers will have maximum efficiencies of 94% to 96%, however, some high-performing boilers may reach efficiencies up to 98%.

•Boiler Performance. The performance features that will affect the price are turn down ratios (the higher the ratio, the higher the price), durability of materials (especially heat exchanger material), ability to control the boiler remotely over wi-fi and other smart control features.

•Boiler Warranty. Different manufacturers will offer different warranty deals for their products which will also affect the final price.

•Adding accessories. Your total boiler cost will higher if you want to install some additional high-value accessories might such as thermostat ($30-$500) or zone controls ($1,000-$3,500).

Cost to install a boiler

Installation costs vary significantly depending on the scope of work that has to be completed. For the boiler only replacement, a $700 to $3,000 bill can be expected.

Depending on where you live plumbers will charge higher or lower rates for their work. On average, plumbing pros charge $65-110 per hour. High income areas such as Massachusetts, New York, Washington State and California can have much higher labor rates, that are over 30% greater than the national averages quoted online for boiler replacement.

If a new hydronic system is required, which includes new pipework with baseboard radiators or new ductwork with air registers, extra $1,200 to $5,000 can be added to the boiler price.

Did you know? Condensing boilers can be installed to an existing system that previously had a conventional boiler installed. This means that your current radiators can effectively work with a new condensing boiler. Sometimes the increased efficiency means your feed and expansion system might not be suitable. However, this is easily overcome by pressurizing the system, which will be done by a pro who will install the new boiler.

Pro Tip: When purchasing a condensing boiler, look for the one with an ENERGY STAR certification. This certification is awarded to those models that achieve high levels of efficiency. Not only this makes sure you will use much less energy in your home, but also enables you to receive tax credits.

For instance, an ENERGY STAR certified boiler with AFUE equal to or higher than 95% qualify for a tax credit amount of $150. In addition, many utility providers offer rebates for high efficiency equipment. To search for incentives in your area, visit the Database of State Incentives for Renewables & Efficiency website (DSIRE) (https://programs.dsireusa.org/system/program/detail/1715).

What is a Combi boiler?

Just like any other boiler type, condensing boilers can be either regular or Combi. A Combi (or combination) boiler is simply a dual-purpose boiler that functions as both central heating device and tankless hot water heater. In contrast, a regular boiler is designed to provide only central heating.

The hot water generation in the combi boiler is done by an additional heat exchanger, which intakes mains cold water and instantaneously heats

how a combi boiler works

(Typical Combi Boiler Distribution Diagram)

Is a Combi boiler better than a regular condensing boiler?

The advantages of the Combi boiler are as follows:

• Compact size: Combi boilers eliminate the need for a large hot water cylinder, cold water storage tanks and any additional water heaters or boilers. Since everything is done within one device, a lot of space and installation work is saved.

• Economical Operation: Unlike hot water cylinders that have to keep domestic hot water hot at all times, whether there is demand or not, combi boilers produce hot water only when it is needed, thus not wasting any energy.

• Fast Access to Hot Water: Since hot water is generated instantaneously, there is no risk of hot water running out or waiting for the hot water cylinder to heat up the full volume again.

Some of the disadvantages of the Combi boiler include:

• Not Suitable for Very High Hot Water Demands: Since a Combi boiler draws all its water supply directly from the mains, it does not have the benefit of a back-up water tank to meet excessively high household hot water demand. Typically, Combi boilers are capable of generating enough hot water flow for a bath and a shower at the same time, or multiple taps and a dishwasher, however, running multiple baths concurrently might be problematic.

In reality, this kind of simultaneous demand is rare in residential conditions and only large homes with multiple bathrooms will experience this drawback. In any case, more than one combi boiler can be installed to meet the expected simultaneous hot water demand.

• Lower Resilience in case of Break Down: Having both central heating and hot water generation in a single device means that, in case of a faulty boiler, both services are lost at the same time.

Did you know? According to the US Department of Energy, for a house that uses 41 gallons or less of domestic hot water daily, tankless water heaters, such as combi boilers, can be 24%-34% more efficient compared to traditional hot water tank heaters.

Pro Tip: To estimate the right size of the combi boiler required for your house, two parameters have to be calculated: space heating demand and domestic hot water simultaneous demand.

For the space heating, a Manual J calculation will reveal how much boiler heating capacity is required to cover all the heating loads, which are typically measured in BTU/hr or MBH (1 MBH = 1,000 BTU/hr).

For the domestic hot water, it is required to estimate the expected maximum simultaneous flow rate and temperature rise. For example, if you expect that you will be running a hot water faucet (0.75gpm) and a shower head (2.5gpm) at the same time, then the total flow rate demand will be 3.25gpm.

For most uses, the required temperature of hot water is 120°F and the incoming mains water temperature is 50°F. Following this example, you would need a combi boiler capable of rising the temperature by 70°F at a flow rate of 3.25gpm to meet the expected demand.

It is best, however, if both calculations above are completed by a professional engineer.

Condensing boiler benefits

Condensing boilers are modern and have many advantages over the other types. In the United Kingdom, since 2007, it has been a legal requirement that all residential boilers installed must be of condensing type. There is no such law in the United States, but it sends a clear message that condensing boilers can bring a lot of benefits to homeowners.

Some of the biggest advantages include:

• High Efficiency. Condensing boilers typically have efficiencies in the range of 88% to 98% AFUE depending on the brand and the model. AFUE stands for annual fuel utilization efficiency and is a measure of heat output compared to fuel energy input over the course of a full year. In contrast, modern non-condensing boilers have AFUE of 80% to 88% and many older boilers which are still in service can have efficiency ratings as low as 50%-70%. Currently, the minimum AFUE ratings as required by the US Department of Energy are 82% for gas-fired and 84% for oil-fired boilers, with the new standards coming into force in 2021 requiring 84% and 87% for the gas and oil-fired boilers respectively.

• Low Operating Costs. Since condensing boilers are generally 10-12% more efficient than conventional ones, the fuel consumption is much lower. Due to lower energy bills, the payback period for condensing boilers may be between 10-15 years, which is equal to or even shorter than a typical condensing boiler life expectancy of 10-20 years, provided that maintenance is not ignored. Upgrading your old boiler with efficiency below 60% to a modern condensing boiler with AFUE higher than 90% can often cut fuel bills almost in half. The table below illustrates potential savings for replacing your existing boiler with a new high-efficiency heating system.

condensing boiler heating efficiency

(Annual Estimated Savings for Every $100 of Fuel Cost by Increasing Heating Equipment)

Did you know? A common myth about condensing boilers is that they are only efficient when operating in condensing mode. A larger heat exchanger area and more advanced controls of condensing boilers ensures higher efficiency values than conventional boilers even on occasions when flue gases are not condensed.

Pro Tip: To increase condensing boiler efficiency, it is crucial to ensure that the return heating water temperature is below 131°F to allow flue gases to condense and transfer its latent heat back to the system. Lower return temperature by decreasing heating water supply temperature set point. Most condensing boilers will have their peak performance at an 80°F return temperature.

Is it worth buying a condensing boiler?

Condensing boilers are designed based on the latest technology which makes them the most efficient on the market. The main reason to buy a condensing boiler is the large saving in fuel consumption and therefore money.

It definitely makes sense to upgrade your 10-20-year old boiler with efficiency below 70% to a condensing boiler with efficiency of 95%. This will typically cut your fuel bill by half, and you will be able to recover the money spent on purchasing condensing boiler within its lifetime.

However, if you currently have a mid-efficiency non-condensing boiler system (80%-88% AFUE) and it is in acceptable working condition, then an upgrade to a condensing boiler will be hard to justify. This is because the cost of the new condensing boiler along with installation is quite high, and the payback period in this case will be uneconomical.

Nevertheless, if a replacement is required due to a faulty boiler or a new-built house requires one, a condensing boiler would still be a recommended choice due to its superior efficiency, lower environmental footprint and improved comfort and convenience through advanced controls.

Regular or Combi Boiler?

Another question is which configuration of heating and domestic hot water production to install – regular heating-only boiler complemented with a hot water tank /tankless water heater, or a combination boiler?

The short answer is: depends on your circumstances. You might have a new water heater in a good working condition at the moment, so replacing your central heating boiler with a regular one would make sense. However, if you are thinking about a new system, combi boilers are tankless and therefore more energy efficient and compact. If your house is not abnormally large with more than two bathrooms, then a combi boiler will offer the most economical solution.

However, if you expect a high simultaneous hot water demand in your home, then a separate hot water tank would make more sense to reduce the risk of not having sufficient hot water flow.

Best 7 Condensing Boilers

A selection of the top 7 recommended condensing boiler models is presented below along with their cost, efficiency, type, capacity range, warranty information, pros and cons.

1. Lennox GWM-IE Boiler

Lennox Condensing Boiler

Cost: $1,675-$6,400

Efficiency: up to 95% AFUE

Available Types and Ranges: Heating-only boilers (50-200 MBH)

Warranty: 15-Year Limited Warranty on Heat Exchanger; 10-Year Limited Warranty on covered components


• Boiler has been designated as one of the Most Efficient ENERGY STAR certified products in 2018
• Boiler has economical electronic ignition switch that monitors temperature and prevents excessive use of the burner
• The heat exchanger tube is self-cleaning and the mesh burner is corrosion resistant, hence reasonably long warranty is offered


• The price may be quite high compared to other brands

2.Bosch Greenstar Boiler

Bosch Greenstar Condensing Boiler

Cost: $3,000-$5,230

Efficiency: up to 95% AFUE

Available Types and Ranges: Heating-only boilers (57-151 MBH) and Combi boilers (100-151 MBH)

Warranty: Lifetime heat exchanger warranty pro-rated after 10th year; 5-year parts and labor warranty


• Boiler comes in both heating-only and combi versions
• Both wall-hung and floor-standing models are available
• Boiler has an advanced Aluminum-Silicon alloy heat exchanger, which offers increased flexibility compared to traditional stainless steel. The heat
exchanger also has a coating that prevents scale build-up extending the life of the boiler and minimizing servicing


• The price may be quite high compared to other brands
• Turndown ratios are slightly lower compared to market average

3. Triangle Tube Challenger Solo and Combi Boiler

Triangle Tube Challenger Solo and Combi Boiler

Cost: $1,785-$2,565

Efficiency: up to 95% AFUE

Available Types and Ranges: Heating-only boilers (50-125 MBH) and Combi boilers (105-125 MBH)

Warranty: Limited 10-year heat exchanger warranty; limited 1-year warranty on component parts


• Boiler comes in both heating-only and combi versions
• The pre-assembled primary-secondary manifold is included with all Challenger boilers. The manifold simplifies the installation saving time and money
• Boiler has compact size which makes it perfect for closet application
• Boiler prices are lower compared to other condensing boilers


• Boiler has aluminum heat exchanger which is less durable and more prone to corrosion than stainless steel

4. Westinghouse Combi Boiler

Westinghouse Combi Boiler

Cost: $2,440-$2,750

Efficiency: up to 96% AFUE

Available Types and Ranges: Combi boilers (140 & 199 MBH)

Warranty: 10-year warranty on the heat exchanger; 5-year parts warranty


• Both floor-mounted and wall-mounted models are available
• Boiler has high turndown ratios – up to 10:1. This allows better match fuel consumption to heating demand, which, in turn, conserves energy and
provides high system efficiency even during low load conditions
• Boiler is fitted with a state-of-the-art leak detection that protects against hazardous gas emissions
• Boiler has ultra-low NOx emissions which reduces the environmental impact


• Only two boiler capacities are available – 140 and 199 MBH

5. Bosch Buderus SSB

Bosch Buderus SSB Condensing Boiler

Cost: $3,365-$8,750

Efficiency: up to 96% AFUE

Available Types and Ranges: Heating-only boilers (85-255 MBH)

Warranty: 10-year limited warranty on the heat exchanger; 5-year warranty on parts and labor


• Boiler has specially built insulation that ensures ultra-quiet operation, as low as 44 dB(a)
• Boiler has extra durable heat exchanger made of 316L stainless steel with no welds
• Boiler has high quality construction as they are designed with the same high-quality components found in the models for commercial applications


• Only floor-mounted models are available
• Minimum capacity available is 80 MBH which might not be suitable for small homes (oversized heating system)
• The price may be quite high compared to other brands

6. Weil McLain WM97+ CT Boiler

Weil McLain Condensing Boiler

Cost: $3,140-$3,950

Efficiency: up to 95% AFUE

Available Types and Ranges: Heating-only boilers (70-155 MBH)

Warranty: 12-year limited warranty on heat exchanger; 2-year limited warranty on all other parts


• Boiler has three thermostat inputs and circulator outputs with selectable priority. This eliminates need and costs of zone control relays
• Boiler has dedicated connection for the indirect-fired water heater with customizable settings. This way, the boiler can be easily partnered with a water
heater if needed.

• Boiler comes with a built-in expansion tank (70 and 110 MBH sizes only) and low water cut-off


• Minimum capacity available is 70 MBH which might not be suitable for small homes (oversized heating system)

7. Laars MFTHW – 199 Condensing Boiler

Laars MFTHW Condensing Boiler

Cost: $1,485-$3,130

Efficiency: up to 95% AFUE

Available Types and Ranges: Heating-only boilers (100-199 MBH) and Combi boilers (140-199 MBH)

Warranty: 10-years limited heat exchanger warranty; 5-year parts warranty


• Both floor-mounted and wall-mounted models are available
• Boiler comes in both heating-only and combi versions
• Combi boiler models use a “hybrid water heater design” which takes the best features of tankless and cylinder type water heating. The boiler has a mini
tank with the capacity of half a gallon which is always kept charged with hot water in order to ensure that the hot water is available as fast as
possible. This is very cost-effective for larger houses with multiple bathrooms, where higher hot water flow rates might be required to meet simultaneous


• Minimum capacity available is 100 MBH which might not be suitable for small homes (oversized heating system)

Compare top boiler brands

Once you decide to install a condensing boiler, it is important to select an appropriate model that matches your budget and expectations. Table below summarizes all the parameters of the top 7 condensing boilers discussed in this article for easier comparison.

best condensing boiler comparison chart

Final Verdict: which condensing boiler is the best?

All models on the list are highly efficient and are eligible for tax credits and rebates. The higher price typically reflects the higher quality of the boiler parts and hence longer life and warranty periods. On average, condensing boilers last 15 years, but with a higher quality components and regular maintenance, the boiler can serve for 20 years and more.

The model that stands out in terms of price-quality relationship is LAARS Mascot FT. For a reasonably low price, it offers a market average 10-year warranty on a heat exchanger and a 5-year warranty on other parts. There is also flexibility in boiler selection: both heating-only and combi boilers are available with a wide range of capacities. The turndown ratios are also above the market average of 5:1.

However, other models might have features that are attractive in your specific situation, For example, if you a want to have a peace of mind offered by the lifetime heat exchanger warranty from the Bosch Greenstar boiler and the heating demand of your house is not high, it might be the right choice for you.

Forced Hot Water Boiler Costs
Gas Boiler
$3900 - $5600
Oil Boiler
$4800 - $6700
Base Boards
$2100 - $3500

See costs in your area Start Here - Enter Your Zip Code

About Yelena G

Yelena G. has been working in the remodeling and construction industry for over 15 years. Her focus is on construction planning and design as well as project cost estimating. Yelena also has a personal interest in interior design, as well as in unique DIY remodeling projects. Read more about Yelena

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