A Complete Comparison Of Condensing Vs Non Condensing Tankless Water Heater

A Complete Comparison Of Condensing Vs Non Condensing Tankless Water Heater

Recent popularity of tankless water heaters as an energy-efficient and space-saving alternative to storage tank water heaters. These innovative devices heat water on demand, eliminating the need for a large storage tank and saving energy.

All tankless water heaters are not created equal. This comprehensive comparison of condensing vs non condensing tankless water heater will compare condensing and non-condensing tankless water heaters. Homeowners must decide which option is best for them because each has pros and cons.

Condensing vs. Non-Condensing Tankless Water Heaters

AspectCondensing Tankless Water HeatersNon-Condensing Tankless Water Heaters
Efficiency RatingUp to 98%80-85%
Energy SavingsHigherModerate
Standby Energy LossesMinimalEliminated
Initial CostHigherLower
Long-Term Operating CostsLowerModerate
VentingPVC pipesStainless steel or galvanized pipes
Environmental ImpactReduced greenhouse gas emissionsSlightly more emissions
LifespanTypically longerTypically shorter

This table provides a quick glance at the key differences between condensing and non-condensing tankless water heaters. Let’s explore condensing and non-condensing tankless water heaters to help you choose one for your home.

This comprehensive comparison will walk you through these cutting-edge appliances’ key features, whether you’re upgrading or installing.

What Are Tankless Water Heaters?

On-demand water heaters, or tankless water heaters, heat water directly without a tank. Tankless water heaters serve hot water only when needed, unlike traditional ones.

How Does Tankless Water Heaters Work?

When the hot water tap is on, cold water enters the tankless heater. The unit quickly heats cold water with powerful heating elements or a gas hob. The unit releases heated water through pipes to your tap or showerhead.

Tankless water heaters provide hot water on demand, a major benefit. This means no waiting for a storage tank to fill before taking a warm shower or doing dishes. It also prevents hot water shortages during peak usage.

Condensing Tankless Water Heaters

Homeowners seeking energy savings and carbon reduction choose condensing tankless water heaters. Innovative units use advanced technology to maximise efficiency and provide hot water on demand.

How Do Condensing Tankless Water Heaters Work?

The secondary heat exchanger in condensing tankless water heaters uses exhaust gas heat. They achieve higher energy efficiency with this process.

Secondary heat exchangers extract heat from exhaust gases before venting them, while primary heat exchangers heat incoming cold water. Condensing tankless water heaters use waste heat to save energy.

Advantages of Condensing Tankless Water Heaters

Higher Energy Efficiency:

Condensing tankless water heaters are more energy-efficient than non-condensing ones due to their ability to capture and use waste heat. This may lower utility bills over time.

Greener option:

Condensing tankless water heaters reduce greenhouse gas emissions by using less energy, making them a greener choice for environmentally conscious individuals.

Continuous Hot Water Supply:

Condensing units provide hot water on demand, preventing runouts during showers or household tasks.

Space-saving Design:

Condensing tankless water heaters save space in your home by being smaller than traditional storage tanks.

Longer Lifespan:

The lifespan of condensing models is longer than non-condensing models due to advanced technology and durable components, resulting in reliable hot water for many years.

Things to Think About

Installation Cost:

Condensing tankless water heaters have higher upfront costs despite long-term energy savings. Over time, energy savings can offset this initial investment.

Venting Requirements:

Flexible venting options are available for condensing tankless water heaters due to their cooler exhaust gases. To avoid safety issues, proper venting must be installed.


Condensing units may need periodic maintenance to remove debris and prevent clogs. To maximise performance, follow manufacturer maintenance instructions.

Non-Condensing Tankless Water Heaters

Consider non-condensing tankless water heaters for your home’s hot water needs. They have several advantages over condensing models, despite their lower energy efficiency.

How Do Non-Condensing Tankless Water Heaters Work?

Non-condensing tankless water heaters heat cold water as it flows through the unit. They lack a secondary heat exchanger to use exhaust gas heat. Powerful burners in the non-condensing unit quickly heat water when you turn on a hot water tap. Thus, it provides hot water on demand without a tank.

Benefits of Non-Condensing Tankless Water Heaters

Lower Initial Cost:

Non-condensing tankless water heaters typically cost less than condensing ones. This can make them cheaper for homeowners.

Simplicity and Reliability:

Non-condensing units are simpler and easier to maintain due to their simple design and fewer components. Long-term reliability and efficiency can come from their simplicity.

Fast Hot Water Delivery:

Non-condensing units heat water directly, delivering hot water almost instantly. This helps when hot water is needed immediately.

Flexible Installation Options:

Non-condensing tankless water heaters offer more installation flexibility due to less complex venting systems compared to condensing models.

Suitable for Warmer Climates:

Effective and efficient non-condensing tankless water heaters are ideal for milder climates with higher groundwater temperatures.

Things to Think About

Energy Efficiency:

While non-condensing units are less energy-efficient than condensing models, they still offer savings compared to traditional storage tanks. The cost savings should be weighed against the higher energy consumption.

Environmental Impact:

Non-condensing tankless water heaters may emit slightly more greenhouse gases than condensing units. Consider environmental impacts if reducing your carbon footprint is important.

Lifespan and Maintenance:

Non-condensing tankless water heaters typically last less than condensing units. To avoid mineral buildup, descaling must be done regularly.

Efficiency and Energy Savings

Efficiency and energy savings are hallmarks of tankless water heaters. We’ll examine how condensing and non-condensing tankless water heaters save energy in this section.

Condensing Tankless Water Heaters

Efficiency is maximised by condensing tankless water heaters. They use a secondary heat exchanger to extract heat from combustion gases. This process boosts condensing unit efficiency to 98%.

Condensing tankless water heaters recover heat that would otherwise be wasted, which is their main benefit. They use less fuel and energy to provide hot water by recovering heat, lowering operating costs.

Non- Condensing Tankless Water Heaters

Although less efficient than condensing tankless water heaters, they still save a lot of energy. Non-condensing tankless water heaters heat cold water directly in the heat exchanger.

These units eliminate storage tank standby energy losses without capturing waste heat like condensing models. Non-condensing tankless water heaters avoid heating and reheating large amounts of stored hot water because they only heat water when needed.

On-demand heating can save 20%–40% more energy than tank-based systems.

Installing Considerations

There are several factors to consider when installing tankless water heaters. If you choose a condensing or non-condensing unit, these factors will affect installation success and efficiency.

Fuel Type/Availability

Consider local fuel availability before buying a tankless water heater. Both condensing and non-condensing tankless water heaters use natural gas or propane. In areas where natural gas is scarce, propane may be an option.

Make sure your tankless water heater works with your fuel type. A plumber or HVAC technician can help you assess local resources and make an informed decision.

Ventilation Needs

Tankless water heaters need proper venting to operate safely and efficiently. Condensing units require special venting because combustion produces condensation.

Condensing tankless water heaters vent with PVC pipes because they can handle more moisture. Due to lower moisture output, non-condensing models need stainless steel or galvanised vent pipes. Installation requires venting knowledge and local building code compliance. Poor venting can affect performance and safety.

 Water Needs and Size

The right tankless water heater size is essential for meeting your household’s hot water needs. Consider bathroom count, appliances and simultaneous hot water needs.

Condensing and non-condensing tankless water heaters vary in size and flow. A professional installer can assess your home’s needs and recommend a suitable unit.

Undersizing the tankless water heater may result in insufficient hot water, while oversizing may waste energy. Optimising efficiency and meeting household needs requires finding the right balance.


What Are The Main Differences Between Condensing And Non-Condensing Tankless Water Heaters?

Secondary heat exchangers in condensing tankless water heaters absorb and reuse waste heat, improving energy efficiency. This new method reduces water heating heat loss.

Instead of capturing waste heat, non-condensing machines immediately heat water. Condensing heaters are more efficient, but non-condensing ones are cheaper, making them a good alternative for individuals on a budget.

How Do Tankless Water Heaters Work?

Tankless, or on-demand, water heaters revolutionize water heating. These devices instantly heat water as it flows through them instead of holding it in a tank.

Cold water enters a hot water tap and is swiftly heated by an electric element or gas hob. This eliminates storage tank wait times and inefficiencies by providing hot water 24/7.

Are Condensing Tankless Water Heaters More Environmentally Friendly?

Absolutely! Condensing tankless water heaters are considered greener. Capturing and reusing waste heat improves energy efficiency and reduces greenhouse gas emissions.

With peak efficiency, these heaters use less fuel and reduce their carbon footprint. Condensing tankless water heaters help households and businesses go green.

What Are The Installation Considerations For Tankless Water Heaters?

Planning is needed to install a tankless water heater. First and foremost, determine if natural gas, propane, or electricity is available in your area. The unit’s safe and effective operation depends on sufficient ventilation.

Venting systems for condensing models must handle moisture. The unit’s size should match the household’s hot water needs. An undersized unit may not fulfil demand, while an excessive one may waste energy.

Which Tankless Water Heater Has A Longer Lifespan?

The lifespan of condensing tankless water heaters is usually longer. Their superior technology and efficient functioning extend their longevity. Condensing models’ secondary heat exchanger decreases unit wear.

However, both types can provide years of reliable service if properly maintained. Descaling and inspecting for problems keeps condensing and non-condensing tankless water heaters working well for longer.


Many factors must be considered when choosing between condensing and non-condensing tankless water heaters. Both types have pros and cons that may influence your choice depending on your needs. The main takeaways from this comprehensive comparison:

Efficiency and Energy Savings

· Condensing tankless water heaters are more energy-efficient as they recover heat from flue gases, resulting in higher efficiency ratings.

· Non-condensing tankless water heaters are still efficient, but may have slightly lower efficiency ratings than condensing models.

Installing Considerations

· Condensing tankless water heaters need a dedicated drain line and proper venting system to mitigate condensation.

· Non-condensing tankless water heaters are suitable for retrofitting into existing plumbing systems and require fewer installation requirements.

These factors and your needs will help you choose between condensing and non-condensing tankless water heaters. Always consult a plumber or HVAC technician to assess your needs and recommend the best option for your home.

Whether condensing or non-condensing, tankless water heaters offer energy savings, space efficiency, and continuous hot water.

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