How efficient are heat pumps? Our tips for optimal performance

With economic uncertainty and environmental crises making news headlines on a daily basis, it’s no surprise that everyone (us included) is looking for ways to make life a little easier. Whether it’s by cutting back on the weekly shop or reducing energy consumption at home, we’re all looking at changing how we live our day-to-day lives.

One of the newer ways to improve the efficiency of the energy in your home is by installing a heat pump. But what are heat pumps, and how efficient are they as a home heating solution? 

To help you decide whether making the switch from a traditional boiler over to a heat pump is right for you, this blog explores the ins and outs of heat pump efficiency. Plus, our home heating experts will share their tips on how to get the most out of your heat pump and keep it working at peak performance.

How is heat pump efficiency calculated?

Heat pump efficiency is typically calculated using a parameter known as the Coefficient of Performance (COP). The COP is a ratio that represents the amount of heat energy produced or moved by a heat pump for the given input of energy (usually electricity). It measures how efficiently the heat pump can transfer heat from a lower-temperature source to a higher-temperature sink.

The formula to calculate the Coefficient of Performance (COP) is COP = Output Heat Energy / Input Electrical Energy Where: Output Heat Energy is the amount of heat energy delivered to the space being heated or the hot water system. Input Electrical Energy is the amount of electrical energy consumed by the heat pump.

In practical terms, a higher COP indicates better efficiency, meaning more heat energy is being produced or moved for a given amount of electrical energy input.

It's worth noting that factors such as the temperature difference between the heat source and the heat sink, the type of heat pump (whether it’s an air source or ground source heat pump), and the operating conditions can all affect COP. Also, real-world efficiency can vary depending on the environment and usage patterns of the system.

How efficient are heat pumps, really?

Heat pumps are growing in popularity, and a major reason for this is how efficiently they’re able to heat our homes. Unlike more traditional heating systems that use electricity or fossil fuels to generate heat energy, heat pumps capture and transfer existing thermal energy from the ground or air. 

This means that they can provide us with more energy than they use, making them an efficient piece of kit.

Now, it’s not quite as clear-cut as this in practice. There’s a whole range of external factors (which we’ll expand on below) that can influence the efficiency of a heat pump, meaning it’s nigh on impossible to determine precisely how efficient yours will be once it’s up and running.

What factors determine a heat pump's efficiency?

Here are some key factors that add to the making of an efficient heat pump:

1. COP (Coefficient of Performance): 

As we mentioned before, the efficiency of a heat pump is often measured by its Coefficient of Performance. This metric represents the ratio of heat output to electrical input. A higher COP indicates greater efficiency.

2. Air source vs ground source:

There are two main types of heat pumps - air source and ground source. Ground source heat pumps tend to be more efficient, as they draw heat from a relatively stable and mild temperature source. Air source heat pumps are also efficient but may lose efficiency in extremely cold or hot climates.

How do heat pumps work? Heat pumps work in similar ways, the only real difference being the source of the heat energy. Air source heat pumps take heat energy from the surrounding air and transfer it into your home via a coolant. Ground source heat pumps take heat energy from (yep, you’ve guessed it) the ground before transferring it to your home using a coolant.

3. Sizing and installation:

This is where employing a top engineer is crucial, as proper sizing and installation are crucial for maximising the efficiency of a heat pump. An undersized or poorly installed unit won't operate efficiently and may experience frequent short cycling, which can reduce its lifespan over time.

What does it mean when a heat pump short cycles? Short cycling is when a heat pump is turning on and off far more frequently than it should, effectively only running for periods of around 5 minutes at a time. If it’s short cycling, your pump will turn off automatically before completing its full heating and cooling cycle, so it won’t be working efficiently.

4. Maintenance: 

Like any household appliance, regular maintenance is essential to keep a heat pump running as it should. This includes cleaning the filters, checking refrigerant levels, and ensuring all components are in good working order every 6-12 months. Think of your heat pump like your boiler; you need to get it serviced annually to make sure it stays in tip-top condition.

5. Climate: 

The efficiency of an air source heat pump system can be affected by the local climate. In freezing temperatures, a heat pump will need to work harder to extract heat from the outdoor air, which can reduce its efficiency. Read our guide on whether heat pumps work in the winter for more information about how temperature may impact your heat pump’s efficiency.

6. Hybrid heat pump systems: 

In some regions, hybrid systems that combine a heat pump with a backup heating source are used to improve efficiency. The heat pump operates in milder conditions, and the backup heating source kicks in when it's cold to pick up any slack and make sure you never end up with a cold shower!

It's essential to consider your specific heating/cooling needs and the climate of the area you live in when evaluating the efficiency of a heat pump for your home. Consulting with a professional HVAC installer can help you select the right system and ensure it is installed correctly for optimal efficiency.

Top tips for maximising the efficiency of your heat pump

1. Insulate the building

Most system installations will require alterations to the structure of a building itself to increase efficiency. The first step in this process is insulation. This is a common way to make a home more energy efficient: it helps a building hold heat for longer within its walls.
 
Alongside this, energy can be efficiently delivered at a lower flow temperature, or the temperature at which water passes through a radiator or underfloor heating, which reduces the amount of heat required. This increases the effectiveness of the heat pump.

Any heating system, whether it uses non-renewable or renewable energy, is likely to work more effectively in an insulated home.

2. Consider installing underfloor heating

Heating distribution systems like radiators and underfloor heating may alter heat pump efficiency.

Low flow temperatures are more effective over larger surface areas, meaning underfloor heating systems are well-suited to heat pumps.

BOXT top tip: If possible, consult with home heating experts when carrying out any remodelling work on your property that involves upgrading or changing the heating distribution systems. These experts will have the know-how and experience to advise you on the best heating and cooling solutions for your home to ensure you can stay at a comfortable temperature all year round.

3. Think twice before using buffer tanks

Buffer tanks, also known as insulation tanks, feature within some domestic heat pump systems to stop the pump from short cycling. They work by keeping the smallest amount of water possible in the pump’s circuit while the heating load is low.

Buffer tanks aren’t always necessary, as most well-designed heating systems should function properly without the requirement of a buffer.

For things to run as they should, the heat pump has to run 10°C hotter than is required to heat the building since buffer tanks have been shown to reduce temperature by 10°C within a system when in use. Such an installation can permanently increase running expenses by 20% without any clear benefit. As a result, the system may have to work more to maintain a desired temperature.

4. Keep your pump at a consistent temperature

By keeping your ground-source or air-source heat pump system at a (fairly) consistent temperature as often as possible, you can reduce how hard it has to work to heat your home. 

Think about it in terms of a car. If a vehicle consistently brakes to very slow speeds, it’s going to take more fuel (or charge if it’s an electric vehicle) to bring it back up to cruising speed. If a driver maintains a manageable speed over long distances, not going too fast or too slow, they’ll reduce the need for braking and acceleration, thus boosting fuel economy overall.

Heat pumps work in a similar way. If you let your heat pump system cool right down, it’s going to have to work far harder to heat back up again and, in turn, use more electricity in the process.

To get around this, we advise setting your thermostat to stay at a specific temperature range; between 18ºC and 21ºC usually works well for most homes. By keeping your heat pump working within this range all through the winter months, you can minimise the amount of energy it consumes while heating your home.

You can read more expert tips and insights in our blog post on whether you should leave your heating on all the time.

5. Only heating the space you need to

One of the most common ways to lose heat in your home is by allowing warm air to escape into unheated spaces, such as an office or spare bedroom.

Although we understand that it is tempting to shut off the heat to a room that’s out of use, this cold space will act as a vortex for the heat you’ve generated elsewhere in your home.

To prevent this, like before, we advise leaving the heating system on all the time while keeping the temperature set at 18ºC. By doing this, you'll lessen the chance of warm air escaping and spend less energy heating a room when it's time to use it.

Explore the possibility of heat pumps in your home with BOXT

With heat pump technologies moving from strength to strength, an increasing number of UK homeowners are wising up to the environmental and financial benefits they can offer. 

Here at BOXT, we’re working hard to make the home heating industry fairer and more affordable for all. We’re real people who, like yourself, want the best energy solutions for your home. After answering a few questions about your home and existing heating system, we'll recommend a heat pump to meet your needs, and give a fixed price for installation, including everything else you may need such as water cylinders and radiators. 

If you're not sure whether a heat pump, hybrid heat pump, or new boiler would be best for your home, use our Live Chat to speak with an expert team member who'll be more than happy to help.