An air-source heat pump is an efficient and eco-friendly way of heating your home without the need for a traditional gas or electric heating system. If you want to reduce your current heating bills while doing your bit for the environment, then read on to find out how you can achieve this with an air source heat pump.
Following a year-long competition, seven UK installations of the Vitocal 150-A domestic air source heat pump (ASHP) from Viessmann Climate Solutions, pre-selected by the judges for their energy efficient system designs, achieved an average measured seasonal efficiency (SPF) or Open Energy Monitor platform Seasonal Coefficient of Performance (SCOP) of 4.1. This is 46% higher than the installer threshold guidance SCOP of 2.8 under the Micro Generation Scheme (MCS) for accessing the government’s Boiler Upgrade Scheme. 2.8 is also the average efficiency reported in the government’s 2021 Electrification of Heat Demonstration Project[1] that recorded data from 427 UK ASHP installations. Viessmann Climate Solutions is a part of Carrier Global Corporation (NYSE: CARR), global leader in intelligent climate and energy solutions.
For homeowners, a SCOP of 4.1 could translate into savings of £261 per year compared to gas at 6.29p per kWh (not including standing charge). This is an illustration and actual savings vary according to gas unit rate, boiler efficiency, electricity tariff, standing charges and household demand.
In 2024, Viessmann Climate Solutions invited its installers to apply to enter a Top of the SCOPs heat pump efficiency competition[2]. The successful 10 finalists had to fit a Viessmann Vitocal 150-A heat pump for heat and hot water on an open-loop system with weather compensation controls, commissioned and ready for monitoring between August 2024 and August 2025. The finalists each received a heat pump monitoring bundle from Open Energy Monitor (OEM), an independent, open-source energy monitoring platform, worth up to £600, to connect their entered property.
OEM’s Heat Pump Monitor dashboard allows installers and/or homeowners to upload, share and compare the real-world, real-time performance data of their heat pump installations via a league table. Electricity consumption, heat output, flow and return temperatures, ambient temperatures, system statuses and other sensor data are collected automatically and sent to the cloud.
Pictured: performance data for 12 months up to January 26th for Top of the SCOPs competition joint winner: Ipswich home by Sun-Lite Group Ltd.Open Energy Monitor’s Heat Pump Monitor allows installers and/or homeowners to upload, share and compare the real-world, real-time performance data of their heat pump installations. Electricity consumption, heat output, flow and return temperatures, ambient temperatures, system statuses and other sensor data are collected automatically and sent to the cloud.
The two joint-winning installations of the Top of the SCOPs competition, with an average SCOP of 4.5 at the 12 month closing date, were a detached 2016 property in Rednal, Birmingham, with fully insulated walls, floors and loft by NMB Heat Pumps; and a 1930s-built detached chalet bungalow in Ipswich, with cavity wall and some loft insulation, installed by Sun-Lite Group Ltd.
The remaining finalists were Custom Renewables and its installation in Aylesbury, Arran Woodford of York, Ecoerne Consulting with a property in Derrygonnelly, Optimus Heating in Horsham and Peter Hamilton of Berwick-upon-Tweed. Three finalists’ data were not collected in full at the competition’s closing date due to connection issues. The currently connected finalists’ live installations can be viewed here in order of their performance over the past 12 months.
“Heat Pump Monitor is regarded by the HVAC industry as the best open source picture of real-world heat pump performance from the top installations in the country, involving 205 different installers and 20 different manufacturers’ products. While the average SCOP among all 252 ASHP installations with independent billing grade metering on the platform is 3.87, installations using the Viessmann Vitocal 150-A heat pump range return one of the highest overall average SCOPs, of 3.96 (as at January 26th 2026). We are delighted therefore to see our seven finalists raise the game within this already highly competitive data set to achieve an average SCOP of 4.1. between August 2024 and August 2025. This uplift is down to their quality heating system design and installation, and we congratulate them,” says Cameron Beech, Head of Product Management at Viessmann Climate Solutions UK.
“Many of our finalists have been designing low temperature heating systems and fitting Viessmann products for a decade or more – their work signals the efficiency wins that are possible for our industry as it goes from strength to strength,” concludes Cameron Beech.
Glyn Hudson, Co-founder of Open Energy Monitor, said, “The biggest winner of the Top of the SCOPs competition is the heat pump concept itself – the data on our platform shows that even in period homes of 100 years old or more and those built in solid stone that heat pumps can be cheaper to run than gas or oil boilers. While Top of the SCOPs is rightly about applauding some of the very best installers in the country, the data suggests that the success of the Viessmann Vitocal range is its ability to work well as a ‘drop-in’ solution to a wide range of installations. Advanced integrated features such as the defrost buffer vessel take care of installation aspects that otherwise fall to the expertise of the installer.”
One of the most common consumer concerns about heat pumps relates to achieving warm room temperatures on the coldest days. During the 12 month period studied, the average temperature of the coldest day was -2 °C. However, the Vitocal heat pumps generated an average flow temperature of 35 °C and an average indoor temperature of a comfortable 19.5 °C. Even in minus temperatures, the average COP, the efficiency measurement for just the coldest day rather than across a year, was 3.0.
Monitoring heat pump performance via Heat Pump Monitor allows installers to analyse and improve their installations over the year and across different outside temperatures.
Many heat pump installations by Viessmann partners connected to the Heat Pump Monitor return a SCOP of 4.5 and above. The ASHP installation on Open Energy Monitor that produces both heating and hot water the most efficiently in the coldest average UK temperature, with a platform SCOP topping 5.4 at certain times of the year, is a Vitocal 150-A in an Edwardian home in Sheffield listed by heating engineer, Damon Blakemore of Blakemore Plumbing, Heating & Renewables.
[1] Electrification of Heat Demonstration Project, Department for Energy Security and Net Zero (DESNZ)
[2] The launch of Viessmann Climate Solutions’ ‘Top of the SCOPs’ competition can be viewed accessed here.
Founded in 1917 as a heating technology manufacturer, today Viessmann Climate Solutions is a leading global provider of sustainable climate (heating, cooling, water and air quality) and renewable energy solutions. The Integrated Viessmann Climate Solutions portfolio seamlessly connects products and systems via digital platforms and services, creating an individualized feel-good climate for users. Viessmann Climate Solutions is part of Carrier Global Corporation, global leader in intelligent climate and energy solutions that matter for people and our planet for generations to come. For more information, visit https://www.viessmann-climatesolutions.com/en.html.
Open Energy Monitor
Glyn Hudson, glyn.hudson@openenergymonitor.org. 01286 800870.
This is where KERS+ Heat Recovery Ventilation makes a major difference.
Mould spores are naturally present in the air, but they only grow when conditions are right. The key ingredients are:
Modern homes, especially those upgraded for energy efficiency with insulation and airtight windows, often trap moisture inside. Everyday activities such as cooking, drying clothes indoors, and even breathing add litres of water vapour to the air each day. Without proper ventilation, this moisture settles on walls, ceilings, and window reveals — creating the perfect breeding ground for mould.
Wiping mould off a wall with spray or bleach may remove stains temporarily, but if humidity remains high, it will return. True mould prevention requires continuous moisture control, not just surface treatment.
That’s exactly what KERS+ is designed to do.
KERS+ is a single-room heat recovery ventilation system that provides constant fresh air while removing stale, moisture-laden air — all without losing the heat you’ve paid to produce.
KERS+ units quietly extract humid air from rooms such as:
By steadily removing moist air, the system prevents humidity from building up to mould-forming levels.
Unlike opening windows — which wastes heat and increases energy bills — KERS+ uses a ceramic heat exchanger to recover warmth from outgoing air and transfer it to incoming fresh air.
This means:
✔ You ventilate your home
✔ You control moisture
✔ You keep the warmth inside
A warm, well-ventilated home is far less likely to suffer from condensation and mould.
Many KERS+ models include humidity sensors that automatically increase airflow when moisture levels rise, such as during showers or cooking. Once humidity drops back to safe levels, the system returns to normal operation — ensuring ventilation happens when you need it most.
This smart control helps stop the damp conditions mould needs to grow.
Condensation is often the first warning sign before mould appears. KERS+ reduces indoor humidity levels, meaning:
Mould releases spores that can trigger:
KERS+ not only removes moisture but also filters incoming air, helping create a healthier indoor environment for your family.
KERS+ is especially effective in:
🏠 Older homes with poor natural ventilation
🏠 Airtight renovated homes
🏠 Apartments without wall vents
🏠 Bedrooms prone to window condensation
🏠 Bathrooms with recurring mould on ceilings
Because it is decentralised (room-by-room), it can be installed exactly where mould problems occur.
Think of KERS+ as a permanent moisture management solution, not just a fan. By keeping air moving and humidity controlled all year round, it addresses the underlying cause of mould rather than just cleaning the symptoms.
Homeowners often notice:
✔ Fresher smelling rooms
✔ Dry windows in the morning
✔ Reduced damp patches
✔ No return of mould after treatment
Mould is a moisture problem — and moisture problems need ventilation solutions. KERS+ Heat Recovery Ventilation removes humid air, supplies fresh filtered air, and retains indoor heat, creating an environment where mould simply cannot thrive.
Instead of repeatedly scrubbing mould away, you can stop it from forming in the first place — and enjoy a warmer, healthier, fresher home all year round.
At the heart of the KERS+ system is a ceramic heat exchanger with hexagonal cells. This structure provides a large surface area for heat transfer and excellent thermal conductivity, allowing the system to recover up to approximately 97% of heat that would otherwise be lost with conventional ventilation.
This ceramic core design is more efficient than many traditional plate heat exchangers and enables the very high thermal recovery percentages KERS+ is known for.
Unlike centralized HVAC systems that serve entire buildings through duct networks, KERS+ operates at perimeter walls in each room.
KERS+ units use electronically commutated (EC) motors for the fans. These combine the efficiency of brushless DC technology with precise speed control, ensuring minimal electrical usage even at higher ventilation rates.
The whole system runs on electrical power lower than a typical LED light bulb, highlighting a very low electrical consumption relative to the volume of heat energy retained.
KERS+ offers multiple ventilation and control modes, enhancing both comfort and efficiency:
These modes ensure ventilation only operates at levels necessary for comfort and air quality, avoiding unnecessary energy use.
KERS+ systems are engineered for low noise — as low as ~7 dB in super-minimum mode and typically attenuating external noise significantly (up to 42 dB).
Efficient noise control encourages users to keep the system operating continuously, which in turn maintains both energy efficiency and indoor air quality.
Most KERS+ models include G3 class filters on both intake and exhaust sides of the exchanger, which:
Because of its efficiency and ventilation quality, KERS+ contributes to:
The high efficiency of KERS+ arises from a synergy of advanced ceramic heat exchange technology, decentralized installation, energy-efficient components, and smart operating modes. These features together create a ventilation system that recovers a large proportion of heat energy, reduces electricity consumption, improves indoor air quality, and enhances comfort — all while minimizing installation and operating costs relative to traditional HVAC systems.
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