Energy Saving Trust verifies that Passiv controls improve heat pump performance by up to 25%

February, 2024

Passiv UK has welcomed the findings of an independent assessment of its heat pump controls by Energy Saving Trust. The assessment concluded that the Passiv controls increase the space heating Coefficient of Performance of a heat pump by 17% and a hybrid heat pump by 25%. This improvement in efficiency can deliver a significant reduction in heating bills for heat pump owners compared with traditional manufacturer or smart thermostat controls.

Using the results from a field trial* Energy Saving Trust analysed data from heat pumps and hybrid heat pumps with Passiv controls from homes across England and Wales. This data was used to calculate the Coefficient of Performance (CoP) for both standard and Passiv controlled systems. The CoP is a measure of heat pump efficiency calculated as the ratio between the electricity consumed and heat output by the heat pump – a higher CoP means a more efficient heat pump and lower energy bills.

Energy Saving Trust verified that Passiv controls increase the average space heating CoP of a heat pump by 0.54 or 17%. For hybrid heat pumps, this figure rises to 0.65 or 25%. Passiv controls also increased the utilisation rate of the heat pump in hybrids from an average of 47% to 82%, resulting in a major reduction in carbon emissions from reduced boiler use.

How does it work?

Passiv controls increase the efficiency of a heat pump by optimising the flow temperature. Passiv uses patented machine-learning algorithms to construct a model of how a home loses heat. The controls use this model alongside local weather forecasts to meet the setpoint requirements of the home with the lowest possible flow temperature. The controls can deliver further energy bill savings by optimising the heat pump according to time of use tariffs and on-site renewable generation.

“With the Government targeting 600,000 heat pump installations a year by 2028 and the recent sharp rise in energy prices, it’s more important than ever that heat pumps are installed with controls that optimise them. We’re pleased that Energy Saving Trust has verified the efficiency improvement delivered by Passiv controls and the unique value we can bring to heat pump owners. A ‘smart thermostat’ isn’t all that smart where heat pumps are concerned. Our controls have been designed specifically for heat pumps to deliver better comfort, simpler control and reduced energy bills.”
Ian Rose, Passiv's Sales & Strategy Director

About Energy Saving Trust

*Energy Saving Trust hybrid heat pump findings are based on field trials between October 2021 to December 2021. A temperature correction was applied to systems not controlled by Passiv to account for any difference in external temperatures. Passiv systems have been controlled to achieve higher utilisation rates by optimising for the Renewable Heat Incentive.

Heat pump findings are based on modelled savings from field trial data, with the models independently verified by Energy Saving Trust. CoP improvement was achieved with no loss of comfort during heating hours. For some homes there may be an increase in the number of hours the heat pump runs, which may affect the overall energy consumption. A correction factor has been applied to account for the overestimation of mean CoP in the modelled data compared to actual data.

Findings are correct as of October 2022.

About Passiv UK

Passiv UK Limited (“Passiv UK”) is a smart energy technology business with over a decade of experience developing software solutions to decarbonise homes. The Passiv Smart Energy Platform provides a smarter solution to the monitoring, control and optimisation of heat pumps, battery storage, solar PV and EV chargepoints. The Platform uses patented machine-learning algorithms to reduce running costs and carbon emissions by improving the performance of low-carbon technologies, increasing efficiency while optimising against time of use tariffs and on-site renewable generation.

Passiv UK is a market-leader in net-zero projects, designing and delivering innovative energy transformation solutions with a particular focus on low-carbon heat. In the last three years, it has completed over 50 projects working in partnership with Government, network operators, energy companies and manufacturers.

Passiv UK was founded in 2008 and employs 50 people. It was first to market globally with a smart thermostat and is the largest installer of hybrid heating systems in the UK. Passiv UK currently manages 50,000 domestic solar installations owned by infrastructure investors, Local Authorities and Housing Associations.

For further information on Passiv UK, visit:

Passiv UK is part of the BUUK Infrastructure Group, the leading independent provider of last-mile utility networks, constructing and operating essential utility assets in the UK. BUUK Infrastructure has a unique integrated approach to providing all the essential utilities; gas, electricity, water, waste water, fibre to the home and district heat networks.

For more information on Passiv UK’s parent company, BUUK Infrastructure, visit: