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Vaillant geoTHERM product photo

The Vaillant geoTHERM has been discontinued but is still available secondhand (image credit: Vaillant)

The Vaillant geoTHERM is a quiet, efficient and highly economical ground source heat pump that makes use of renewable energy. Installing the Vaillant geoTHERM can significantly reduce heat loss in well-insulated homes, lowering your fuel bills and improving the comfort of the occupants. 

The Vaillant geoTHERM ground source heat pump comes with weather compensating controls as standard to provide optimum efficiency. A clear LED display demonstrates how much energy is being extracted from the ground, so you can see how effectively your unit is working at all times. 

The Vaillant geoTHERM also received a Quiet Mark award, which makes it one of the quietest units on the market. In a clear demonstration of the trust Vaillant has in the quality of their heat pumps, the company offered a 10-year guarantee on their heat pump compressors and a 7-year parts and labour guarantee on their heat pumps if installed by a professional and approved installer. 

The geoTHERM is available in a range of outputs: 22kW, 30kW, 38kW and 46kW. The heat pump was also certified by the Microgeneration Certification Scheme (MCS), a nationally recognised scheme that acknowledges and rewards high standards in renewable energy technology. 

Unfortunately, Vaillant has discontinued the geoTHERM ground source heat pump. They may be purchased on the secondhand market, without warranties applicable, at a lower price. 

Vaillant still produces excellent quality ground source heat pumps in the form of the Vaillant flexoTHERM range.

Editor’s note

The Vaillant geoTHERM has now been discontinued. Therefore, we recommend that this review should be used for informational purposes only and if you’re considering buying this ground source heat pump secondhand.Read our guide to the best ground source heat pumps to see what other options are available.

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Technical information

The geoTHERM is available in a range of outputs to suit a variety of homes: 22kW, 30kW, 38kW and 46kW. The geoTHERM is a sustainable energy source, certified by the MCS scheme (Microgeneration Certification Scheme), which means that homeowners could benefit from Renewable Heat Incentive (RHI) payments by installing a geoTHERM ground source heat pump. 

  • Guarantee options: 10-year guarantee on the heat pump compressor (new models only, check with merchant for guarantee on second hand product)
  • Price range: £8,000 – £11,000
  • Efficiency: A++
  • Max power: 46kW

Key features

Highlights: Quiet Mark and MCS certification

Key benefit: The 10-year warranty is the longest for any heat pump compressor on the market

Maximum flow temperature: 62°C

Dimensions: 1200mm (h) x 760mm (w) x 900mm (d)

Vaillant geoTHERM installed in a home

Vaillant ground source heat pumps are easy to maintain (image credit: Vaillant)

Pros and cons 

A ground source heat pump is an excellent investment for your home, but it’s an expensive one. Before making a decision, it’s important to evaluate all of the options available to you. Some of the benefits of the Vaillant geoTHERM include: 

  • Highly efficient: The Vaillant geoTHERM ground source heat pump is highly efficient with an A++ ErP rating at 55°C. 
  • Quiet: The Vaillant geoTHERM is Quiet Mark-certified and makes no more noise than a standard dishwasher.  
  • Warranties: The main heat pump compressor carries a lengthy 10-year warranty, while another warranty offers up to 7-year coverage for parts and labour if installed by a renewable partner. It is worth noting these warranties only apply to new models, not secondhand. 
  • Smart displays:  A number of useful Vaillant apps and control panels display how much energy is being extracted from the ground, making it easy to keep an eye on your heat pump’s performance. 

While the Vaillant geoTHERM is an impressive product, there are some disadvantages to keep in mind:

  • Discontinuation: Unfortunately, Vaillant has discontinued the geoTHERM heat pump. While it’s still available on the secondhand market, these secondhand heat pumps do not come with warranties. 
  • Cost: At £8,000 plus (without installation and labour), the Vaillant isn’t the most affordable model on the market. 

How does the Vaillant geoTHERM series heat pump work?

The Vaillant geoTHERM ground source heat pump uses thermal energy from the ground via deep boreholes. The energy extracted is passed through the compressor and turned into efficient heating and hot water. 

The Vaillant geoTHERM contains a high-efficiency evaporator with an injection system which boosts the heat transfer process within the ground source heat pump, making it extremely effective at heating.

Heat generation is controlled and monitored by advanced sensors. The heating system, ground loop collector, anti-freeze function and continuous pressure measurement in the refrigerant circuit ensure an optimal level of comfort is maintained at all times. The sensor control monitors the refrigerant circuit without requiring additional measuring equipment.

How does the Vaillant geoTHERM ground source heat pump compare to other heat pumps?

valliant smart control console product shot

The Valliant smart control console can help improve efficiency (image credit: Vaillant)

If you want to stay in the Vaillant family, you should consider the Vaillant flexoTHERM. The flexoTHERM has slowly replaced the geoTHERM as it’s being phased out, and its efficiencies are comparable. The flexoTHERM is suitable for large homes and commercial properties. 

If, however, you own a flat or smaller property, it’s best to skip the Vaillant flexoTHERM and geoTHERM. Kensa offers an excellent heat pump for smaller homes called the Kensa Shoebox. It fits seamlessly in an airing cupboard or broom closet and costs less than £4,000 per unit (excluding installation and labour). 

Alternatively, if you are after more power for a larger property, check out the Viessmann Vitocal 350-G. The Viessmann Vitocal 350-G ground source heat pump offers heating outputs of between 20.5kW to 84.6kW, depending on the unit. It’s priced in a similar way to the flexoTHERM, but it’s not as easy to customise. 

What does the Vaillant geoTHERM ground source heat pump cost?

The Vaillant geoTHERM ground source heat pump is a premium unit and priced accordingly. Here’s how it compares to other units with similar outputs:

ManufacturerCost (excluding installation and labour)
Vaillant geoTHERM 19kW£11,000
Viessmann Vitocal 350-G£10,000
Vaillant flexoTHERM 19kW£11,000

Maintaining the Vaillant geoTHERM

The Vaillant geoTHERM doesn’t require a lot of maintenance, but it’s important to make basic checks before the winter weather sets in. Homeowners should check the inhibitor levels for corrosion or degradation and make sure that all pump valves and actuators, room stats and programmers are functioning correctly. Components that require batteries should have a charge, and the filters should be cleaned. 

Vaillant geoTHERM add-ons

There aren’t specific add-ons on offer for the Vaillant geoTHERM ground source heat pump, but Vaillant has a range of accessories that are likely compatible with the unit. Make sure to ask your installer about the possibility of adding accessories, including passive cooling modules or adapters. 

What the professionals say

“The upfront costs of a ground source heat pump and the installation are much higher than a conventional boiler. However, they can last twice as long as boilers and could help to lower your heating bills. Plus, RHI payments can potentially see you make a return on that investment. Vaillant ground source heat pumps are efficient, reliable and quiet heating systems available in a range of outputs to suit the heating demands of different homes.”

“This model is highly effective when replacing an LPG or oil system, as its low running costs will guarantee you a great cost reduction. Furthermore, you will be protected from the oil price fluctuations while also reducing the negative impact on the environment. This model also has been certified with the Quiet Award.”

“Vaillant ground source heat pumps are a highly efficient and economical renewable energy solution, making them ideal for homes looking to reduce their carbon footprint and lower their fuel bills. They’re also quiet and reliable heating systems that come in a broad range of outputs to suit different properties and requirements. If you want to modernise your heating system and help save the planet, a ground source heat pump from Vaillant is an excellent renewable alternative to your traditional boiler.”

Customer reviews

“The installation, although by its nature was a bit disruptive, was very well handled and went smoothly. The plumbers and electricians from Pink Heating were knowledgeable, friendly and careful to do the best job possible with the minimum possible disruption. As it is now edging into summer, the system has not really been tested yet, but all seems fine so far and works well. The flexibility of control of individual room temperatures via a phone app is excellent.”

“Working fine, except that the heat pump often (always?) carries on until the temperature is higher than that for which it is set. Also, it is annoying to have an extra screen/menu requiring `zone 1` to be named every time I want to change time settings.”

“More user info required as instructions are fairly poor and short. Otherwise, apart from being noisier than I expected, the heat pump is an excellent way to heat my house, lower my carbon footprint and save me money.”

Final verdict

While the Vaillant geoTHERM ground source heat pump has been discontinued, it’s still available for purchase, and homeowners should jump at the chance to own one, especially if prices come down accordingly. 

The Vaillant geoTHERM is far from the cheapest brand we’ve reviewed, but it’s not the most expensive either. Its A++ ErP rating, Quiet-Mark certification make it an attractive option – even on the second hand market. 

The Vaillant geoTHERM ground source heat pump fits neatly into your smart home environment, with a range of apps and innovative control panels that help homeowners stay on top of their heat pump at all times. 

We would recommend the geoTHERM for large homes and commercial properties as multiple units can be linked together to create an efficient cascade system. It’s quiet enough to fit comfortably in shared spaces and compatible with radiators and underfloor heating. 

The Vaillant geoTHERM also comes with excellent weather compensating controls to ensure optimal comfort for occupants at all times. If you want flexibility, power and efficiency that will last for at least 20 years, then the Vaillant geoTHERM is a solid choice. 

Our methodology 

This review was compiled with careful consideration after reading hundreds of customer reviews (including those found on Reddit, Trustpilot and Google), consulting professional forums, studying technical documentation and reviewing media articles. We then scored the Vaillant geoTHERM out of a total of one hundred points, comprised of the following: 

  • The warranty period offered by the brand, for a total of 10 points;
  • The overall reputation of the brand is based on online reviews, for a total of 15 points;
  • Trustpilot reviews for a total of 5 points;
  • Awards and accolades (e.g. Which? Best Buy Awards) for a total of 5 points;
  • Customer service performance, for a total of 10 points;
  • The price range, for a total of 15 points;
  • Efficiency ratings, for a total of 15 points; 
  • Installation and maintenance network and reviews, for a total of 15 points; and
  • The total warranty period for a total of 10 points.