Your guide to heat pump efficiency
Heat pumps are well known for being eco-friendly. But another key benefit is that they’re also incredibly efficient. Here, we’ll explore all you need to know about heat pump efficiency – from what makes heat pumps efficient to why it matters.
But first…
How efficient are heat pumps?
Heat pumps are around three or four times more efficient than gas boilers.
In fact, the most efficient boilers can reach around 98% efficiency. But air source heat pumps can reach around 300% efficiency!
If you’re wondering how that’s possible, consider that heat pumps don’t actually create heat. Instead, they transfer it from one place to another, using a small amount of electricity.
This is far more energy efficient than generating heat from scratch.
What’s the typical heat pump energy consumption?
Heat pump electricity consumption is typically very low.
In fact, heat pumps generate more heat than the electricity we use to power them.
This is because just 25% of the energy used by an air source heat pump is typically provided by electricity. The rest is generated by the environment through the air.
A heat pump’s exact electricity usage will vary depending on lots of different factors. But as a rough guide, an air source heat pump could deliver anywhere between 1.5 and 4 kilowatts (kW) of heat for every 1 kW of electricity it consumes.
What is the Coefficient of Performance in heat pumps?
The Coefficient of Performance (COP) of a heat pump is a measure of how efficiently it performs.
Essentially, the COP is the ratio of heating capacity and total power input.
For instance, a COP of 2.5 indicates that, at a steady state, you generate 2.5 kW of heating capacity by using 1 kW of electric power. Here, we assume that the heat pump is driven by an electric motor, which is usually the case.
Depending on the weather, the COP of a heat pump can rise to around 4.
Another similar measure of performance is the Seasonal Coefficient of Performance (SCOP) – also known as the Seasonal Performance Factor (SPF).
Unlike the COP, the SCOP takes into account the fact that external temperatures can affect a heat pump’s efficiency. It does this by summing up the heat that is generated per year and dividing it by the total electric energy use.
For air source heat pumps, this is calculated by dividing the total ambient temperature range into sub-intervals and defining the duration of each.
Heat pumps should generally be expected to generate SCOPs of 2.5 or higher. Which means a year-round COP of 2.5 or higher.
What determines air source heat pump efficiency?
As we’ve touched upon already, there are lots of different factors that have a bearing on the efficiency of a heat pump.
Here are some of the main ones.
Ambient temperatures
As the temperature of the air outside increases, a heat pump’s COP will also increase.
This is because the compressor inside the air source heat pump won’t need to work as hard to reach the required flow temperature.
With that in mind, two identical heat pump systems will perform differently in two different climate areas.
This shows how important it is to check the conditions behind a heat pump’s stated COP, to make sure it’s been tested at realistic ambient temperatures.
System design and installation
A heat pump system design must be finely tuned to take into account the unique needs of a building and its occupants.
That’s why our experienced system designers will create a bespoke system that takes into account your business’ exact requirements.
In this way, they can ensure your entire system is working with you to ensure the highest COPs possible – including your building’s wider infrastructure such as the emitters.
Which brings us onto…
Emitters
Generally speaking, the higher the outlet temperature of the heat pump, the more work the compressor inside the heat pump has to do to achieve the required temperature.
This will lower the COP of your heat pump.
That’s why heat pumps usually perform best when they’re paired with larger radiators or underfloor heating, which require a lower inlet temperature to provide the same space heating as a traditional boiler.
However, there are exceptions.
Any of our CO2 heat pumps are MORE efficient at higher output temperatures because of the unique thermodynamic properties of CO2. We take advantage of this to provide temperatures up to 80C with COPs over 3.0. Check out our Acer and Maple heat pumps to see what we mean.
Heating needs
How you use your heat pump system – and what you require of it – can affect your COPs.
For instance, is there a big heating demand at a certain time of the day? Do you need a heat pump for space heating only, or for space heating and domestic hot water?
Factors like these will affect what kind of heat pump system you need and how hard your heat pump has to work to provide the desired heat output.
Refrigerant
Your choice of refrigerant gas can also affect your heat pump’s efficiency.
Natural refrigerants tend to be particularly efficient in heat pumps, as they have no glide.
This is a thermodynamic behaviour found in some synthetic refrigerants, which suits cooling and refrigeration but not heating.
In fact, in heat pumps, natural refrigerants achieve higher coefficient of performance (COP) at low ambients and high flow temperatures than synthetic refrigerants.
At Clade, we only work with natural refrigerants. After all, they’re both high-performing and environmentally friendly – making them the best option for both people and the planet.
Why does the efficiency of heat pumps matter?
Now you understand a bit more about heat pump efficiency, it seems like a good time to address a simple question… why does it all matter?
Well, heat pump efficiency will have a strong bearing on a few of key elements.
Energy bills
First things first, the more efficient your heat pump is, the lower your energy bills will be.
Think about it. The less electricity your heat pump uses to keep your building warm and toasty, the less electricity you’ll have to pay for.
Electrification of heat with a heat pump also opens up the opportunity to make the most of dynamic tariffs. Known as grid flexibility, this will be a key part of our energy future.
Carbon emissions
Air source heat pumps emit no point-of-use carbon emissions.
However, much of the UK’s electricity is still generated by fossil fuels (although the proportion of renewable energy supplied to the National Grid is increasing).
So, unless you power your heat pump using a renewable energy source such as solar or wind, you’ll still be generating a small amount of carbon emissions indirectly.
With that in mind, the more efficient your heat pump is, and the less electricity it uses, the smaller its impact on the environment.
What are the most efficient heat pumps?
At Clade, we have some of the most efficient commercial heat pumps on the market.
We typically see COPs in our heat pumps between 3 and 4 – sometimes even higher depending on the conditions.
The high performance of our heat pumps is largely due to our 35 years of experience manufacturing heat pumps and refrigeration equipment.
But it’s also down to our selection of refrigerants.
At Clade, we only use natural refrigerants, which tend to achieve higher COPs at low ambients and high flow temperatures than synthetic alternatives.
In particular, many of our heat pumps contain CO2 (also known as R744) as the working fluid. CO2 has a higher pressure compared to many other refrigerants, which allows it to provide high-grade heat and higher COPs than other options.
This means that a CO2 heat pump could provide domestic heating (for hot water and radiators) at up to 85°C while maintaining a high COP.
How important is heat pump heating efficiency?
As you’ve probably already gathered, choosing an efficient heat pump is really important.
However, it’s not the only factor to bear in mind.
For instance, you could easily take a super efficient heat pump model and get very poor performance out of it.
Similarly, you could manage to get great results from an older, less efficient unit by connecting it to a fantastic system.
With that in mind, a great SCOP rating doesn’t by itself equal the most efficient system with the lowest possible running costs.
Rather, there are other factors to take into account as well, which can improve or detract from a heat pump’s efficiency.
How to improve heat pump efficiency
Here are some steps you can take to improve your heat pump’s efficiency.
Optimise your heating distribution system
Heat pumps are different to gas boilers and therefore need different distribution or heating systems to function at peak efficiency.
It is vital that the heating system is designed specifically for the heat pump selected because they work as a team to deliver heat efficiently.
The size of the heat emitter surface area matters, as does the flow control. So, the designer has to use a combination of VSD pumps, control valves and balancing valves to achieve optimal performance.
Once installed it is really important that time is spent commissioning and optimising the system performance.
No system is perfect at first. So, the team should spend time looking at the data and making adjustments to the system in order to achieve the best possible performance.
Think carefully about buffer tanks
A buffer tank – also known as a buffer vessel or thermal store – holds heated water so that the heat can be used later. Kind of like a battery!
The idea is that this heated water is ready to travel straight to your radiators or underfloor heating when you need it.
This has lots of positives – your heat pump doesn’t have to turn on and off constantly to meet demand. And your buffer can cover the start-up time for a heat pump to get to temperature and then absorb excess heat during shut-down so there’s no waste.
However, if used improperly, a buffer tank can work against a heat pump’s efficiency. This is because it can reduce temperature by around 10%.
If you have a full flow passing through your buffer constantly, this means the heat pump then has to operate at a temperature 10% hotter than necessary, adding to your running costs.
Instead, if you do opt for a separate buffer tank, it’s best that it’s only connected with two pipes. This way, it works as a bypass route and is only used when needed. Which leads us to…
Avoid mixing flow and return water
Heat pumps are deliberately designed to have a high flow temperature with a cooler return temperature.
With that in mind, any part of your heating system that allows the warm flow water to mix with the cooler return water (without taking useful heat from it) will normally reduce your heat pump’s efficiency.
The areas where this tends to happen are buffer tanks that have four connections (as we touched upon above), as well as thermal stores and low loss headers that don’t have the flows balanced.
Steer clear of multiple small water pumps
Water pumps help to move your heat pump’s refrigerant around the system, as well as moving hot water into your building’s emitters.
However, the more that you improve your heat pump’s efficiency, the more of its electricity usage will be driven by these water pumps.
With that in mind, it’s often wise to avoid dotting multiple small pumps around a system.
Instead, fewer pumps that are correctly sized will typically demand less energy. Plus, as an added benefit, this will usually be quieter.
Talk to us about efficient heat pumps
As you can see, we know a lot about heat pump efficiency – and we’ve only just scratched the surface!
If you’re on the lookout for an efficient heat pump for your business, you’re in the right place.
Our team of experts will be happy to scope out your project and design a bespoke heat pump system that takes into account your unique heating and temperature needs, to make sure it’s as efficient as possible.
Simply get in touch to start the conversation!