Nicola Gresty, Energy and Carbon Programme Manager, Salix
Decarbonisation has emerged as a dominant trend across public, private, and domestic sectors since the UK government’s 2019 commitment to achieving net zero emissions by 2050. Initiatives such as the Public Sector Decarbonisation Scheme (PSDS) have been instrumental in advancing this agenda, particularly within the public domain, and have formed a core part of my role at Salix.
A significant focus has been placed on enhancing building efficiency by reducing heat demand through a fabric-first approach. This involves upgrading elements such as double or triple glazing and cavity wall insulation. When combined with the installation of low-carbon heating technologies such as heat pumps, organisations can significantly reduce their reliance on fossil fuels, particularly natural gas.
The impact of the Public Sector Decarbonisation Scheme has been substantial, with more than 1.2 million tonnes of carbon dioxide saved annually. However, this raises a critical question: how can we be certain that the reported savings are accurate? As earlier phases of the Public Sector Decarbonisation Scheme have concluded, they’ve laid the groundwork for annual carbon reporting.
Once organisations have operated their new heating systems for at least a year, they are required to report on their energy usage. Yet, it has become clear that monitoring and verification (M&V) are often overlooked once the initial decarbonisation goals are met.
So, what exactly is M&V and why is it essential? This question is increasingly relevant for grant recipients entering the post-completion phase. Monitoring refers to the collection and recording of performance data, while verification ensures the accuracy and reliability of that data. Within the context of the Public Sector Decarbonisation Scheme, M&V pertains specifically to carbon savings.
Low-carbon heating systems, like any technology, may not always perform as expected. This makes ongoing monitoring crucial for providing a detailed, year-on-year assessment of actual carbon reductions. In the Public Sector Decarbonisation Scheme, M&V plays a pivotal role in evaluating the effectiveness of government-funded low-carbon solutions across a wide spectrum of public sector organisations, from NHS trusts and police stations to primary schools.
One key tool in this process is Heating Degree Day (HDD) data, which helps quantify savings by accounting for variations in weather. For instance, if the baseline year was unusually warm, heating demand would have been lower, potentially skewing results. Heating Degree Day data normalises these anomalies, offering a more accurate and proportional comparison across different time periods and geographic areas. This methodology is embedded in the Public Sector Decarbonisation Scheme annual carbon reporting, enabling public sector bodies to assess performance and strategically plan future sustainability initiatives.
While validating carbon savings is essential, effective Monitoring and Verification (M&V) goes further, creating a valuable feedback loop that informs future decision-making. When organisations can identify underperforming systems, they gain insight into where energy efficiency opportunities are being missed. This enables early interventions, enhancing both financial returns and environmental impact.
The integration of digital technologies, such as smart meters, supports this process by enabling real-time performance tracking. This reduces reliance on manual reporting and enhances transparency across operations.
However, the success of M&V depends not only on technological solutions but also on cultivating internal expertise. Many public sector organisations face resource limitations, highlighting the need to upskill staff in areas such as carbon accounting, data analysis, and system optimisation. This need is increasingly evident through our engagement with Public Sector Decarbonisation Scheme grant recipients.
The data collected through schemes like the Public Sector Decarbonisation Scheme has the potential to inform national policy, spotlight best practices, and shape future funding models. In this way, M&V contributes not only to accountability but also to collective learning across the public sector.
By continuing to gather and analyse this critical data, we have the opportunity to showcase the environmental and financial value of decarbonisation projects. It’s not just about measuring impact at the point of installation, it’s about understanding how those impacts are sustained and improved over time.
Looking ahead, I believe that any new or ongoing decarbonisation efforts must be underpinned by a robust M&V strategy. This will empower organisations to confidently link installed measures to actual carbon savings, paving the way for more predictable and impactful outcomes.
We remain optimistic about the future. As the UK advances toward its 2050 net zero target, the role of M&V will become increasingly vital. By embedding M&V into our organisational culture, we move closer to a future where carbon savings are not only projected but also proven.
This article appeared in the Nov/Dec 2025 issue of Energy Manager magazine. Subscribe here.