18 Dec 2024

Coefficient Of Performance - CO2 vs R13a


At The Cylinder Guy we want to help you make the best decision if you are looking to get a hot water heat pump system. Hot water heat pump systems are highly efficient and environmentally friendly, however, not all of them are created equal.  

Two of the main refrigerants found in hot water heat pumps are CO2 and R134a, and these have different impacts to the environment and cost effectiveness. This blog will explore the Coefficient of Performance (COP) of both refrigerants and their environmental impact, while also helping you make an informed decision for your new or updated hot water heat pump system. 


Understanding Coefficient of Performance (COP)  

COP is a critical metric when evaluating the energy efficiency of a heating or cooling system. It represents the ratio of useful heat output to the energy input required to produce it. The greater the COP, the more efficient your system is. This is essential in understanding the difference between a hot water heat pump model with CO2 or R134a as the refrigerant. 



CO2 Cylinders: The Green Revolution 

CO2, often referred to as R744 in refrigeration terminology, is a natural refrigerant that has gained popularity due to its low Global Warming Potential (GWP) and Ozone Depletion Potential (ODP). When used in hot water cylinders, CO2 systems can achieve impressively high COP values. This makes them a sustainable choice for those seeking to minimize their carbon footprint. 


Advantages of CO2 Cylinders: 

Low Environmental Impact: CO2 has a GWP of 1, making it an excellent choice for environmentally conscious consumers. 

High COP Values: CO2 systems can achieve COP values well above 4, indicating a highly efficient heating process. 

Renewable Energy Compatibility: CO2 systems can be integrated with renewable energy sources, such as solar or geothermal, further reducing their environmental impact. 

R134a Cylinders: Established, and advantaged 

R134a, a hydrofluorocarbon (HFC), has long been a standard refrigerant in various applications. However, its high GWP of 1,430 has led to concerns about its environmental impact. Despite this, R134a hot water cylinders are still in use. This is because they come with many advantages, such as being well established and widely used, making them readily available. They also have a history of reliable performance, providing consistent hot water. 

Environmental Considerations 

When choosing between CO2 and R134a hot water heat pump systems, it's important to weigh the environmental impact. While R134a systems offer familiarity and reliability, CO2 systems are the more sustainable choice due to their significantly lower GWP, not to mention they also are more cost efficient, and you know they are doing good work for the environment. CO2 hot water heat pumps often have a controller which makes it easier and more convenient to manage your energy needs and use. You are in control of when and how your hot water system works for you. The CO2 hot water heat pumps demonstrate exceptional performance in cold weather conditions, eliminating the necessity for an additional electrical element to support water heating. 

One limitation of R134a is that it has difficulty reaching temperatures above 60℃ without additional heating. This means that in applications where higher temperatures are required, such as certain industrial processes or specialised applications, R134a alone may not be sufficient. 

To address this limitation, many R134a -systems are equipped with a back-up heating element. This element provides additional heat when the temperature needs to exceed the natural capabilities of R134a. The back-up element kicks in when the refrigerant alone is unable to achieve the desired temperature, ensuring that the system can meet the specific heating requirements. 



CO2 Hot water heat pumps use a technology that offers a distinct benefit over traditional R134a models. Unlike standard R134a systems, CO2 Hot water heat pumps feature a design that allows for single pass heating over 60 degrees Celsius. This means that CO2 Hot water heat pumps can achieve higher temperatures without the need for a back-up element. This can be a significant advantage in situations where precise and consistent high-temperature control is critical. 

The ability of CO2 Hot water heat pumps to provide single pass heating over 60 degrees Celsius can lead to increased efficiency and potentially lower energy consumption, as it eliminates the need for additional heating elements. Additionally, it may have implications for the overall design and cost-effectiveness of systems utilising CO2 hot water heat pumps technology. 

In summary, R134a models typically rely on a back-up element to achieve temperatures over 60 degrees Celsius, CO2 hot water heat pumps technology offers a distinct advantage by enabling single pass heating at these higher temperatures without the need for additional heating elements. This can lead to more efficient and cost-effective systems in applications where precise temperature control is crucial. 

In the quest for sustainable and energy-efficient hot water heat pumps solutions, the choice between CO2 and R134a cylinders can be difficult. While R134a systems are known for their reliability, it's also important to consider the environmental benefits of CO2 cylinders. As we collectively move towards a greener future, opting for CO2-based systems can make a significant contribution to reducing greenhouse gas emissions. It's important to note that when it comes to hot water heat pumps, both options excel compared to other hot water heating systems.  


Here at The Cylinder Guy we offer hot water heat pumps with either refrigerant. Providing a balanced selection, making sure we have an option for what you want and need. Ultimately, the decision depends on your individual preferences, budget, and the desire to align with environmentally conscious practices. Whichever choice you make, ensuring proper installation with The Cylinder Guy will optimise the performance of your chosen hot water cylinder system. 


Contact our friendly team if you’d like to learn more about different hot water heat pump options. 


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