How to Maximize Condensing Boiler Efficiency and Select the High Efficiency Condensing Boiler?

Best Condensing Gas Boiler

Condensing boiler efficiency is already high compared to other steam boilers. But do you know that you can increase the efficiency even more? It will help you save money and get optimal results with your boiler. Therefore, it’s vital to know the reasons for decreased boiler efficiency.

A common issue that lowers a boiler’s efficiency is pipework temperature. While it is a major problem, it’s not the only one. Several other factors can make your condensing boiler inefficient. 

This guide will present some solid facts regarding condensing boiler efficiency in detail. It will help you make the system more efficient. We will also list down and explain the types of condensing boilers, so that you can find the best one. Let’s begin!

What Is a Condensing Steam Boiler?

A condensing boiler is one of the most efficient types of boilers. It uses oil or gas as fuel to offer higher energy efficiency. Although it is also common in households, the boiler has major industrial applications. Generally, it is used as a water heater for heating systems and reduces energy waste. 

The condensing boiler efficiency is one of the biggest reasons why people choose this boiler. That’s because these make the most of input using heat from natural gas combustion and unused energy sources. A condensing boiler’s heat exchanger is the key component to executing these processes. It also turns the vapor into water droplets. 

Finally, the boiler drains all the obtained water into its neutralizer. There, the water resides with other byproducts gained from the combustion.


Types Of Condensing Boilers

There are two main types of condensing boilers; system and combi boilers. The combi boiler is suitable for small industries having higher water pressure, while a system boiler is ideal for larger industries with low water pressure. 

However, a condensing boiler can also be classified into more types based on its size, shape, and application. Considering your requirements, you can find the right option that suits your needs. 

That said, let’s take a look at its four main types:

1. Floor Boilers

A floor boiler has many names, including a floor-mounted or a floor-standing boiler. It is often compared with wall-mounted boilers due to its comparatively larger size. But it can also produce steam and hot water of a greater volume.

2. Wall Mounted Boilers

Due to their small size, these are the most popular type of condensing boilers out there. Wall-mounted boilers come in various industrial sizes. They are commonly installed with a modular boiler arrangement. 

3. Heat Only Boilers

Heat-only boilers are also commonly known as Regular boilers. Their two main components include a tank and a cylinder. They require water in the cylinder to start working. As you continue giving it water, it starts storing in the tank for later on-demand usage. 

Their biggest benefit is that they do not require pressure to work properly. At the same time, these boilers can be incompatible with a new industrial condensing gas boiler heating system. 

4. System Boilers

System boilers are comparatively simpler and better than heat-only boilers. That’s because they only have 1 primary component, the tank. Their other parts include an expansion vessel and pump. Since it does not have a cylinder, system boilers feed water directly.

Condensing Boiler Efficiency

The condensing boiler efficiency is often questioned, considering it is one of the most efficient boilers. It offers 90-97% efficiency, reaching even up to 98 or 99%. This efficiency is a big step up as most conventional boilers are only 75-80% efficient. It is safe to say that condensing boilers have the upper hand in this aspect. 


What’s the reason for this high condensing boiler efficiency? The one-word answer is its heat conversion rate. It minimizes the energy waste and uses energy from different sources. The boiler’s heat exchanger extracts the thermal energy from burning fuel. 

A condensing boiler extracts potential energy from the condensation processes. That is possible by extracting the water vapor. Then, this energy is transferred to the heating system. All of this usable energy gives condensing boilers the edge over gas or electric boilers as they offer up to 15-20% higher efficiency. 

However, there’s a catch. You would not get the higher 90-97% efficiency from a condensing boiler at a higher water temperature. They require a return water temp of 80 degrees Fahrenheit or lower. If you want to get maximum efficiency, the key is to provide a lower water temperature. 

How To Improve Condensing Boiler Efficiency?

A condensing boiler can reach even up to 99% efficiency. But what if you are stuck at a much lower rate? Luckily, there are some ways to increase the condensing boiler efficiency. Let’s go through some effective tips:

graph of condensing boiler efficiency

Flow Temperature

The first and simplest way is to manage the flow temperature. Condensing boilers are designed to consume more gas to release energy. You can eliminate this problem by lowering the temperature of the flow. It will help you save gas and still release consistent energy. 

Adjusting the flow temperature depends on the weather conditions. You can manage it every day, considering the cold intensity.

Water Temperature

Water temperature plays an integral role in determining condensing boiler efficiency. Lowering it can increase efficiency significantly. It is recommended to keep the return water temperature at 80°F or below. This way, you can expect up to 97% efficiency from your boiler. 

However, most people keep the return water temperature at 120° to 160°F. You can only get up to 87-89% efficiency in such conditions.

Deep Temperature Schedule

Another effective and easy method is to schedule a deep temperature reset. That means considering the outdoor temperature and resetting your supply water temperature accordingly. If a deep reset is not feasible, try adjusting the terminal units.

Lower Firing Rates

A condensing boiler is the most efficient when operating at lower firing rates. The expert tip is to opt for multiple boilers with lower firing rates. It will eliminate the need for a single boiler with a higher rate.

For instance, you can use two boilers at 40% each instead of relying on one at 80%. Even better, you can use up to three or four boilers for a better outcome.

How to choose Non-Condensing and Condensing Boilers

You will get a clear answer according to the following context about how to choose the condensing boiler and the non-condensing boiler. Besides the condensing boiler efficiency, non-condensing boilers differ from them in some other aspects. The following table highlights all the major differences condensing vs non-condensing boiler:

Decisive Factors Condensing Boilers Non-Condensing Boilers
Energy Efficiency Condensing boiler efficiency calculation is at 90% efficiency, up to 98%. The non condensing boiler efficiency is at 70-80%, depending on various aspects.
Cost Efficiency Condensing boilers are more cost-effective in the long run but have a high initial cost. Non-condensing boilers have a lower initial cost for purchase and installation. But they are not very cost-effective in the longer run.
Gas Recycle A condensing boiler is capable of recycling exhaust gas through the heat exchanger. Non-condensing boilers waste 30% of the exhaust heat.
Temperature Management A condensing boiler transfers its thermal energy to the heated water. The non condensing boiler temperature is very hot, up to 400°F. Thus, it is emitted out via a chimney.
Heat Exchanger Typically, condensing boilers have larger heat exchangers. And most types have more than one.  Non-condensing boilers usually have only a single heat exchanger.
Complexity Condensing boilers are designed with more sophisticated units and components. Thus, they are comparatively more complex. Their straightforward build makes these boilers significantly simpler to understand and operate.

Advantages and Disadvantages of Condensing Boilers

Condensing boiler efficiency is its biggest benefit, but there are more advantages. It also has some downsides you should know before buying this boiler. Let’s look at its benefits and drawbacks to help you make the final decision.

Advantages Of Condensing Boilers

Condensing Boiler technology

1. A Green Option

Are you concerned about a boiler’s impact on the environment? Then, go for a condensing boiler. It has a significantly lower carbon footprint of 5.2 tonnes per year, while non condensing boilers have about 7.95 tonnes per year. 

2. Save Money

Are you tired of expensive fuel bills? Condensing boilers are highly efficient and can help to lower your fuel expenses. They utilize all the given energy to offer up to 99% efficiency. Additionally, their large heat exchangers can provide better results than non-condensing boilers.

3. Safe and Convenient

Generally, condensing boilers are convenient in shapes and sizes. They can fit in smaller places due to their portable build. Plus, their heating units are more secure than older and inefficient non condensing boilers.

Disadvantages Of Condensing Boilers

1. More Complex

For a newbie, operating a condensing boiler can be overwhelming. It has more controls and units than an average non condensing boiler.

2. Expensive at First

A new condensing boiler can be more expensive than expected.. Although it is very cost-effective, its initial price is quite an investment.


The condensing boiler efficiency is way higher than many conventional boilers. And that is why it gets the upper hand in industrial uses. It can make the most of the given energy to release heated water effectively. But other than the condensing boiler efficiency curve, it has many other benefits. 

The boiler can help lower your costs and be a more convenient option. You can maximize its efficiency by using daily practices to get the best results. However, it can be a bit complicated for an inexperienced individual.

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