Summary of this article: When choosing an air-to-water heat pump, your provider will consider the hardware type, output range, flow temperature, refrigerant, efficiency, and what the model is best for. This isn’t a one-size-fits-all decision and is completely unique to your home, which E.ON Next can calculate with a home survey.
If you’re new to the world of air source heat pumps, choosing the right option for your home can feel a little daunting – but it’s not as tricky as you might first think.
When you install an air source heat pump with E.ON Next, their experts handle all heavy lifting, saving you hassle, time and stress. Their four-step journey starts with an accurate price quote after asking you some questions, followed by an in-person survey to ensure the solution is bespoke and suitable for your home.
It’s important to remember that choosing a heat pump isn’t a one-size-fits-all decision and will completely depend on factors such as property size, heat loss calculations, your existing heating system and insulation. Here’s everything you need to know about choosing an air-to-water heat pump, using the Vaillant aroTHERM Plus and Worcester Bosch Compress 2000 AWF as examples.
How do I choose an air-to-water heat pump?
When it comes to choosing an air-to-water heat pump, you will need to consider the following:
1. Hardware type
There are two main types of hardware: monobloc and split systems. Monobloc systems are the most popular choice, making up 69% of the total UK market share in 2019, according to the Heat Pump Manufacturing Supply Chain Research Project, with all of its components contained in a single unit located outdoors.
A split system, if you couldn’t guess from the name, is split between an indoor and outdoor unit with a connecting refrigerant pipe. According to the above report, monobloc hardware is “simple, relatively low cost, and – unlike split systems – does not require F-gas qualified installers”.
Both the Vaillant aroTHERM Plus and Worcester Bosch Compress 2000 AWF are monobloc systems, which are excellent options provided by E.ON Next.
2. Output range
Next up, you’ll want to think about output range. This is the range of heating power your pump can produce in kilowatts, and is fundamental to your heat pump’s running costs and efficiency. This is completely unique to your home and is calculated based on heat loss, which E.ON Next works out during the in-person survey.
The Valliant model comes in an output range of 3.5kW–12kW, while the Worcester Bosch comes in 4kW–30kW, giving you plenty of options to choose from depending on the specific needs of your home
3. Flow temperature
Flow temperature is the temperature of the water that enters your heating system. This will be set based on the type of equipment being installed and the specific requirements of your property.
The Vaillant aroTHERM Plus can reach up to 75°C, while the Worcester Bosch Compress 2000 AWF can reach up to 65°C, according to the manufacturer websites. One benefit of installing a heat pump with these higher temperature capabilities is that it may be possible to use it with existing radiators that require higher operating temperatures, as Vaillant confirms on its website.
However, a study in the Journal of Applied Engineering found that it’s most energy-efficient to run your heat pump at the lowest possible temperature, which will be defined as part of the bespoke system design stage.
4. Refrigerant
When your provider selects the appropriate heat pump for your home, they will also consider which type of refrigerant is best for your needs, helping to lower your energy bills and save electricity.
The Vaillant aroTHERM Plus uses R290, a natural refrigerant with very low global warming potential and good energy performance, while the Worcester Bosch Compress 2000 AWF uses R32, which offers excellent efficiency and performance at low temperatures.
5. Efficiency
The more efficient your heat pump is, the less you’ll spend on energy bills, so it’s definitely worth getting it right. Heat pump efficiency is measured by COP, which is the heat output divided by the electricity input – the higher the number, the better.
Both models have excellent COP ratings, with the Vaillant aroTHERM Plus scoring up to 5.03 and the Worcester Bosch Compress 2000 AWF scoring up to 4.95. For context, the average COP for air source heat pumps is 3.72, according to Nature Communications.
However, it's worth bearing in mind that these scores are estimates based on testing conditions, and the efficiency will ultimately depend on the individual design on your property – not just the unit itself. Efficiency figures will be shared with you as part of your installation proposal based on your home and selected heat pump.
6. Ease of installation
Switching to a new heating system might feel a long-winded process, but it's surprisingly simple when you choose to install with E.ON Next.
Their MSC-accredited installers handle everything – from the initial quote and suitability check to the installation and certification. They'll also be there to help with any questions you have before, during and after. A typical installation usually takes up to five days depending on the complexity and number of upgrades required.
Here’s a quick comparison of the Vaillant aroTHERM Plus and Worcester Bosch Compress 2000 AWF:
| Row 0 - Cell 0 | Vaillant aroTHERM Plus | Worcester Bosch Compress 2000 AWF |
Hardware type | Monobloc | Monobloc |
Output range | 3.5kW – 12kW | 4kW – 30kW |
Flow temperature | Up to 75°C | Up to 65°C |
Refrigerant | R290 | R32 |
Efficiency | Up to 5.03 | Up to 4.95 |
If you’re interested in installing an air source heat pump, the experts at E.ON Next will be able to recommend the best model for your home, including all of the factors mentioned above.
