PHAM NEWS | MARCH 2026 Heat Pumps


Year-long study proves efficiency


Results from a monitored UK installer competition show that Viessmann air source heat pumps can deliver higher-than- expected efficiencies, highlighting the importance of system design and commissioning.


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ollowing a year-long competition, seven UK installations of the Viessmann Vitocal 150-A domestic air source heat pump (ASHP),


selected 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 Microgeneration Certification Scheme (MCS), and higher than the 2.8 average reported in the government’s 2021 Electrification of Heat Demonstration Project, which recorded data from 427 UK ASHP installations. For homeowners, a SCOP of 4.1 could


translate into savings of £261 per year compared to gas at 6.29p/kWh (excluding standing charges), although actual savings vary according to tariffs, boiler efficiency, standing charges and household demand.


Top of the SCOPS In 2024, Viessmann invited installers to enter its ‘Top of the SCOPs’ heat pump efficiency competition, with candidates required to install a Vitocal 150-A heat pump for heating and hot water on an open loop system with weather compensation, commissioned between August 2024 and August 2025. Finalists received a heat pump monitoring bundle from Open Energy Monitor (OEM) to connect their properties. OEM’s Heat Pump Monitor dashboard


allows installers and homeowners to upload and compare real-world performance data, including electricity consumption, heat output, temperatures and system status, via a league table. The two joint-winning installations


achieved an average SCOP of 4.5: a 2016 detached property in Rednal, Birmingham, installed by NMB Heat


Pumps; and a 1930s detached chalet bungalow in Ipswich, installed by Sun- Lite Group Ltd. Other finalists included Custom Renewables (Aylesbury), Arran Woodford (York), Ecoerne Consulting (Derrygonnelly), Optimus Heating (Horsham) and Peter Hamilton (Berwick- upon-Tweed).


Real world results Cameron Beech, head of product management at Viessmann, says the platform provides “the best open- source picture of real-world heat pump performance from the top installations in the country,” noting that the average SCOP across 252 independently metered installations is 3.87 and 3.96 for the Vitocal 150-A range. He adds: “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.” Glyn Hudson, co-founder of Open


Energy Monitor, adds: “Even in period homes of 100 years old or more and those built in solid stone, heat pumps can be cheaper to run than gas or oil boilers. 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.” Monitoring enables installers to analyse


and optimise performance across different external temperatures. Many installations by Viessmann partners connected to the Heat Pump Monitor return a SCOP of 4.5 and above. In the monitoring period, the coldest day averaged −2°C, with the heat pumps delivering an average flow temperature of 35°C and indoor temperatures of 19.5°C. The average COP on the coldest day was 3.0. ◼ phamnews.co.uk/326/35


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Intatec Limited Airfield Industrial Estate, Hixon, Staffordshire ST18 0PF t. 01889 272180 e. sales@intatec.co.uk www.intatec.co.uk


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