Choosing a heat pump
Best Air Source Heat Pump: What I Recommend and Why
Vaillant, Viessmann and Stiebel Eltron are my first choices. The house and heating design determine which I recommend.
Published
Ask a heating engineer which heat pump is best and you may get a longer answer than you wanted. I will start with the useful bit.
My first choices for the best air source heat pump are Vaillant, Viessmann and Stiebel Eltron. These are the top-end brands I would look at first. The choice between them comes down to the house, the heating design and what matters most to you.
That is my starting point, not a rule that every house must fit. The best air source heat pump is the one that suits your property, works well with its heating system and can be properly maintained afterwards.
Which heat pump brands do I recommend?
Vaillant, Viessmann and Stiebel Eltron make my shortlist. This is my recommendation, not a claim that one manufacturer wins every comparison in every house.
| Brand | Why it is on my shortlist |
|---|---|
| Vaillant | A go-to choice for straightforward systems, with good controls and a quiet new aroTHERM plus range. |
| Viessmann | A top-end choice, with controls and efficiency I rate highly. |
| Stiebel Eltron | An excellent top-end option and one of my first choices alongside Vaillant and Viessmann. |
I do not pick the heat pump first and then try to make the heat-loss calculation agree with it. We establish what the house needs, then choose equipment that can deliver it.
Vaillant, Viessmann or Stiebel Eltron?
Most installations I design have a fairly straightforward heating circuit and an unvented hot-water cylinder. The radiators or underfloor heating can receive a steady supply of heating water without lots of separate circuits repeatedly closing down.
Vaillant and Viessmann have been my usual starting points for that sort of installation. Stiebel Eltron is now alongside them on my shortlist.
Where the new Vaillant aroTHERM plus stands out
The new Vaillant's reduced protection zone gives us more flexibility with positioning. That can make a real difference around doors, windows and other features of the property. It does not remove the need for airflow or servicing access. My aroTHERM plus clearance guide explains the separate requirements.
It is also very quiet. If we are considering a position near a bedroom window, the new Vaillant is my go-to starting point. I still assess that particular location: a quiet product does not make every position suitable. Vaillant sets out the current range on its new aroTHERM plus product page.
When Viessmann might be the better fit
Sometimes the model outputs line up better with the property's heat loss. Sometimes the layout or the customer's preferences make the decision. I am comfortable recommending either brand when it is the right fit.
The important output is what the particular model can deliver at our design outdoor temperature and the water temperature the heating system needs. The number in the model name does not tell you all of that.
Stiebel Eltron is also one of my first choices
I have been looking closely at Stiebel Eltron and rate it as an excellent top-end option. It belongs alongside Vaillant and Viessmann when I am discussing the best heat pumps, not as an afterthought.
There is no need to name one winner for every home. I would compare the models that suit your heat loss, the available space and how your heating system will run.
What do you get by spending more?
With Vaillant and Viessmann, the differences I value are controls, appearance and efficiency. Whether those are worth the extra money is a decision for the customer, with the actual quotes in front of them.
| Difference | What it means for you |
|---|---|
| Controls and app | How easily you can adjust schedules, temperatures and settings, and what extra equipment is included. |
| Efficiency | Potentially less electricity for the same heat, but the installation and operating temperatures still matter. |
| Appearance and noise | How the outdoor unit looks and sounds where it will actually sit. |
| Support | Who helps if it develops a fault, and whether your installer knows the equipment. |
Vaillant and Viessmann have manufacturer apps I rate highly. Check that the quote includes the necessary connectivity equipment; an app logo in a brochure is not an itemised parts list. Viessmann's ViCare guidance explains its connection requirements.
You do not have to spend your evenings adjusting a heating app. Most people want a comfortable house and a schedule that works. Our heat pump controls guide explains the useful differences.
Which heat pump is the most efficient?
Vaillant and Viessmann give me the best efficiency results in my own installation experience. That is one reason they are at the top of my shortlist.
But I would not promise that changing the badge alone will produce the lowest bill. The water temperature, radiator or underfloor output, controls and quality of commissioning all affect the result.
Compare published figures at the same test conditions, then ask how the proposed system will run in your house. A result measured with low-temperature heating water is not a fair comparison with one measured at a much higher temperature.
For real-world efficiency results, have a look at HeatpumpMonitor. You can compare measured performance from installed systems. Remember that you are comparing the whole installation, not just the heat pump brand.
A bigger model is not automatically an upgrade either. It needs enough output for winter, but we also want it to run sensibly when the house needs much less heat. Our heat pump sizing guide explains why.
What should you ask an installer before choosing?
I welcome customers researching the equipment and double-checking my recommendations. You are buying a heating system you will live with for years. Asking why I have chosen something is completely reasonable.
| Ask this | What you need to understand |
|---|---|
| Why this model and size? | How its cold-weather output matches the calculated heat loss. |
| What water temperature are you designing for? | Whether the existing radiators are suitable and which changes are necessary. |
| Why put it there? | Airflow, noise, access and the manufacturer's protection-zone requirements. |
| What controls are included? | The controller, app connection and handover you will receive. |
| Who looks after it afterwards? | Servicing, fault support, warranty conditions and who you contact. |
I attend breakdowns, so a good engineer support network carries a lot of weight with me. The person installing the equipment also needs to be comfortable maintaining and supporting it afterwards.
My recommendation is to compare the whole proposed installation, not just the outdoor unit. Start with a sensible shortlist, establish what the property needs, and ask the installer to explain the pros and cons.
Common questions about choosing a heat pump
What is the best air source heat pump in the UK?
My first choices are Vaillant, Viessmann and Stiebel Eltron. Which one I recommend depends on the house, its heat loss and the heating design. I would compare suitable models from those brands rather than pick one winner for every property.
Is Vaillant better than Viessmann?
I rate both highly. The new Vaillant's siting flexibility and quiet operation can influence my choice, while the available model outputs and the property's requirements can favour either brand. I would compare the actual models proposed for your home.
Would you recommend a Stiebel Eltron heat pump?
Yes. I rate Stiebel Eltron as an excellent top-end option and include it among my first choices alongside Vaillant and Viessmann. The final choice still needs to suit the property's heat loss and heating system.
Which brand gives the best efficiency?
Vaillant and Viessmann have given me the best results in my installation experience. That is not a universal ranking: heating water temperatures, sizing, controls and commissioning all affect efficiency in the finished system.
Is there a best heat pump for an old house?
There is no single brand reserved for old houses. Calculate the heat loss, assess the radiators and consider practical insulation improvements. Then select a model that can deliver the required heat at the proposed water temperature in cold weather.
Should I choose the heat pump before choosing the installer?
Research brands and make a shortlist, but keep the final choice open until the house has been assessed. Ask the installer why they recommend that model and whether they are comfortable maintaining and supporting it afterwards.
Choosing a heat pump for your home in Lincolnshire?
At Vector Heat, we assess the house, design the heating and explain the equipment options. We can talk through where a more expensive system is worth it and where a different choice makes sense.
Find out about our heat pump installation service, or browse our heat pump guides.
