Improve Your New Heat Pump: 9 Tips for Unbeatable Efficiency

In a previous blog I compared, the efficiency and benefits of heat pumps versus gas condensing boilers. While heat pumps offer significant environmental and energy efficiency advantages, achieving their full potential and maximising their financial benefit depends heavily on the design and operation of the system, to make it as efficient as possible. In this blog, we will dive deep into the key factors that make a heat pump system as efficient as possible, from selecting the right unit for the climate to designing a low-temperature distribution system.

1. How to Choose the Perfect Heat Pump for UK Climate

The performance of a heat pump is closely tied to the climate in which it operates. In the UK, where winter temperatures are relatively mild compared to some other regions, careful selection of a heat pump and its refrigerant is crucial for maximising efficiency and minimising environmental impact.

Cold Climates within the UK

In areas of the UK that experience colder winters, such as parts of Scotland or northern England, heat pumps designed to perform well in low temperatures are vital. Systems using refrigerants like R744 (CO₂) excel in these conditions, maintaining efficiency even when outdoor temperatures are near or below freezing.

Milder Climates in the UK

For most of the UK, where winters are less severe, heat pumps using refrigerants such as R32 are a popular choice. R32 offers excellent efficiency and has a lower Global Warming Potential (GWP) compared to older refrigerants like R410A. Its performance is well-suited to the moderate ambient temperatures typically found across much of England and Wales. This article by Hamworthy explains why properties such as the refrigerants boiling point really matter. In general heat pumps are classified into 4 categories. (average, warmer, colder and DHW) in the Uk most of us require average heat pump, and a installer will only install heat pumps suitable for the area. You may have to ask questions however around the GWP of the refrigerant.

As the UK continues to prioritise sustainability and reduce its carbon footprint, choosing a heat pump that utilises low-GWP refrigerants is becoming increasingly important. For example, R32 has a GWP of 675, while R290 (propane) has a significantly lower GWP of just 3 and Carbon dioxide just 1, making them environmentally friendly options that align with the UK’s net-zero goals.

Seasonal Efficiency

When choosing a heat pump, focus on models with a high Seasonal Coefficient of Performance (SCOP). This rating measures how efficiently the system operates over an entire heating season, providing a realistic picture of its performance under UK weather conditions. Older heat pump may advertise SCOP of 3, whilst newer more efficient models may advertise a SCOP of 5. If you want to delve even deeper about componets of a heat pump and their constrction check out this article which tackle the finer details of cost per kW of energy saved.

Resolve’s Optimisation Tip

Ensure the heat pump you select includes performance data for the lowest expected outdoor temperature in your area. For instance, if temperatures in your region can drop to -5°C, confirm that the heat pump remains efficient at this temperature without relying heavily on backup heaters. This guarantees year-round comfort and minimises energy use. Do not hesitate to change installer if a different manufacturer provides a heat pump more suited to your needs. Installers tend to only supply a few manufacturers.

2. Proper Heat Pump Sizing is Key to efficiency

Selecting the right size heat pump for your property is essential to ensure efficient operation and reliable performance. An undersized heat pump will struggle to meet the peak heating demand during cold spells, the efficiency will drop and the cost sky rocket. While an oversized heat pump will be more costly. Under sizing is particularly problematic in the UK, where winter temperatures can drop significantly. To avoid this, your installer will conduct detailed heat loss calculations that consider:

• The building’s size and layout.
• Construction materials and insulation levels.
• Airtightness and ventilation rates.

These calculations ensure the heat pump can meet the property’s peak heating demand, even in the coldest conditions.

Buffer Tank Considerations

In some cases, installing a buffer tank can stabilise the system and prevent short cycling, particularly in properties with low thermal mass or where the heat pump is working with a low-volume heating system.

Resolve’s Optimisation Tip

Always work with an accredited installer who can accurately calculate the heat load of your property and recommend the appropriately sized heat pump. This ensures the system can handle peak load conditions while maintaining efficient operation throughout the year. Do not let your installer use rule of thumbs or previous experience without crunching the numbers.

3. The Magic of Low Flow Temperatures

Minimising the flow temperature of a heat pump system is key to maximising its efficiency. The heat pump’s Coefficient of Performance (COP) improves as the temperature difference between the heat source (e.g., outdoor air) and the flow temperature decreases. This is due to the properties of the refrigerant.

Target Flow Temperatures

• Underfloor Heating (UFH): Aim for flow temperatures of 30–40°C, as UFH systems are highly effective at low temperatures due to their large surface area.
• Oversized Radiators: Design for flow temperatures of 45–50°C, achievable with properly sized radiators and good system design.

Low energy demand

A well-insulated home with minimal air leakage helps retain heat, enabling the heat pump to maintain lower flow temperatures without compromising comfort. Resolves expertise lies in consulting on fabric first upgrade. We can help crush the heating demand and make the lowest flow temperatures possible. We believe that reducing your energy demand is a pivotal first step in most cases before installing a heat pump.

Resolve’s Optimisation Tip

Conduct a full passive house modelling process to identify issues of heat loss. Most insulation, improved airtightness and glazing upgrades can be recommended first to make your heat pump smaller but also more efficient. A lower temperature will be required to heat your home.

4. Large Emitters for Maximum Heat Pump Performance

Efficient heat distribution is essential for optimising a heat pump system. As previously mentioned, Heat pumps perform best when operating at low flow temperatures, and large surface area emitters, such as underfloor heating (UFH) or oversized radiators, make this possible.

Underfloor Heating (UFH)

UFH is considered the gold standard for heat pump systems in the UK. By distributing heat over a large surface area, it provides consistent warmth at flow temperatures as low as 30–35°C. This is significantly lower than the 60–70°C flow temperatures typical of traditional radiator systems, resulting in a much more efficient operation.

Oversized Radiators

For homes where retrofitting UFH is impractical, upgrading to oversized radiators is an effective alternative. Larger radiators have an increased surface area, enabling them to deliver sufficient heat at lower flow temperatures, making them a suitable option for heat pump compatibility.

Resolve’s Optimisation Tip

Design the emitter system to maintain the desired room temperature at the lowest achievable flow temperature. This involves conducting detailed heat loss calculations for each room and matching the emitter type and size to its specific requirements. This approach ensures both comfort and system efficiency. Large volume system helps prevent large heat pumps from short cycling.

5. One Flow Temperature to Rule Them All

Maintaining a consistent flow temperature across the entire heating system is key to maximising the efficiency of a heat pump. Systems with mixing valves or varying temperature zones can reduce performance, as heat pumps operate most efficiently at a steady, low flow temperature.

Eliminate Mixing Valves

Avoid configurations that use mixing valves to blend higher-temperature water with lower-temperature circuits. Such setups force the heat pump to generate unnecessarily high temperatures, which undermines efficiency and increases energy consumption. Design the system so all emitters operate at a single, consistent flow temperature. This approach simplifies system controls and allows the heat pump to perform at its optimal efficiency level.

Resolve’s Optimisation Tip

A whole house with underfloor heating to maintain a consistent low flow temperature across the property is optimum. The emitter size determines the temperature in the room, not the water temperature. Electric radiators can be used to supplement if needed, such as in bathrooms. Infrared are the most efficient.

6. Room-by-Room Temperature Design

Every room in a home has unique heat loss characteristics influenced by factors such as insulation quality, the number of external walls, and the presence of windows. Designing a heat pump system with these specifics in mind ensures efficient operation and consistent comfort.

Room-Specific Calculations

Conduct a detailed heat loss assessment for each room. This calculation determines the exact heat output required to maintain a comfortable temperature. Properly sizing the emitters (e.g., radiators or UFH loops) to match the room’s heat demand prevents inefficiencies caused by oversizing or under sizing.

Flow Temperature Design

Design each room’s heating system to use the lowest flow temperature possible while meeting its largest heat demand. The emitters in each room should have sufficient surface area to achieve this. For instance:

• Rooms with underfloor heating can often operate at flow temperatures as low as 30–35°C.
• Rooms with oversized radiators may need slightly higher temperatures but should still align with the overall system design.
• Bedrooms might be designed with surface areas to create 18-degree temperatures for sleeping whilst living rooms may require higher density of UFH to achieve 21 degrees and bathrooms 22.

7. High Flow Rates to Supercharge Heat Pump Efficiency

Maintaining a high flow rate in the heating system improves heat transfer, minimises temperature drops, and ensures the heat pump operates efficiently.

System Design

• Ensure the pipework and circulation pump can sustain high flow rates.
• Use larger-diameter pipes to reduce resistance and ensure a balanced flow across all emitters, which helps optimise heat delivery.
• Design the system to minimise bottlenecks or restrictions that could impact flow rates.

Resolve’s Optimisation Tip

Regularly balance the system to maintain consistent flow rates across all emitters. Include flow meters and balancing valves in the design for precise adjustments and long-term system efficiency.

8. Bigger is better for DHW Cylinder with a Low Temperature Set Point

When designing a heat pump system, the domestic hot water (DHW) cylinder is a critical component that influences efficiency and overall energy use. Selecting a large DHW cylinder with a low set-point temperature can optimise performance while meeting household hot water demands effectively.

Lower Set-Point Temperature

A set-point temperature of 45°C is sufficient for most domestic applications in the UK There is no minimum storage temperature, but including a legionella cycle (periodic heating to 50- 60°C depending on duration) is standard on modern heat pumps. Operating at a lower temperature reduces heat loss from the cylinder and lowers energy consumption, enhancing the overall efficiency of the heat pump. In this Heat Geek video they explain the risk of legionella and how using the majority of the water in the cylinder each day prevents stagnation, reducing the risk of legionella bacteria developing. When the tank is regularly emptied and refilled with fresh water, the need for additional high-temperature safety cycles is minimised, further supporting energy efficiency.

Benefits of a Larger Cylinder

A larger DHW cylinder ensures:

• Sufficient hot water for daily household needs without the need for frequent reheating cycles.
• Compatibility with the efficient operation of heat pumps, as the system can heat water over longer, slower cycles at lower temperatures, reducing energy demand and improving the Coefficient of Performance (COP).
• Better volume to surface area, means less heat loss.

Resolve’s Optimisation Tips

1. Choose a well-insulated cylinder to further minimise heat loss. Modern cylinders often come with high-performance insulation to keep water hotter for longer.
2. Work with an installer to size the cylinder correctly based on your household’s typical hot water usage. A tank that aligns with daily usage avoids both under-utilisation and excessive energy consumption.
3. Along with other smart innovations, Mixergy have designed a tank which can change the volume of water heated dependant on what your demand is, saving the heating of the entire tank when it is not needed.

9. How to Optimize Your Heat Pump’s Location for Peak Efficiency

The physical placement of a heat pump system plays a vital role in its efficiency and performance. Minimising distances between key components helps reduce energy losses and ensures the system operates as effectively as possible.

Minimising Refrigerant Line Length

The refrigerant circuit should be as short as possible to minimise losses and improve performance. Extensive pipework not only increases the potential for energy losses but also adds complexity and costs to the installation.

Close Proximity to the House

Position the external heat pump unit as close to the house as possible. This reduces the length of pipework required for the flow and return lines between the heat pump and the property, limiting heat loss and enhancing overall system efficiency.

Resolve’s Optimisation Tip

Ensure that the external unit is located in a well-ventilated area with good airflow to avoid overheating. Avoid positioning the heat pump in spaces where airflow is restricted (e.g., in corners or near walls), as this can impact efficiency. Read about best practices with external heat pump placement in this blog from Sentridge UK.

Conclusion

By focusing on these key aspects—proper sizing, low flow temperatures, large emitters, consistent temperature control, DHW optimisation, and smart placement—you can optimise your heat pump system for maximum efficiency and reliability. Our team at Resolve are experts in heat pump consulting and can help you implement these best practices, ensuring your system delivers optimal performance year-round.