Case study: decarbonising Enfield’s social housing

Case studies · News · 27 Oct 2026

On this page

• What is the project?
• What the project delivered
• Zero Carbon Accelerator support
• Funding opportunities identified
• Challenges and how they were addressed
• Lessons learned
• Collaboration
• Energy and carbon impact of the project
• What comes next?

What is the project?

Project stage: Plan and Prepare

Scaling solar energy is crucial to London’s ambitions and the Mayor’s Accelerated Green pathway, which aims for net zero carbon by 2030. The Mayor of London’s Zero Carbon Accelerator directly supports the achievement of this goal.

The Enfield Council project was focused on turning a financed solar concept into investable and procurable retrofit packages for social housing. It was delivered through the Zero Carbon Accelerator, with support from Alliance members, Energiesprong UK and Mott MacDonald.

Initiated by Enfield Council, this was one of the first projects supported by the Zero Carbon Accelerator. It focused on accelerating landlords’ access to finance for housing decarbonisation. It also looked at how to scale low-carbon energy solutions including solar PV, battery storage and heat pumps across London’s social housing stock.

The original brief was to develop a pipeline for around 1,200 flats suited to financed solar and to support Enfield to prepare for procurement. During the project, the scope expanded to include houses. This allowed the team to test similar approaches across different stock types. It also supported Enfield’s wider targets of EPC C by 2028 and EPC B by 2030.

What the project delivered

The final analysis covered 1,219 houses and 2,981 flats. It grouped 4,002 homes into five procurable packages and produced business case reports for each package. The project explored both on-balance-sheet and off-balance-sheet options. These included Enfield-funded delivery using grants, Housing Revenue Account (HRA) investment or borrowing. The team also assessed turnkey models where a third party could finance, operate and maintain the assets. The analysis provided robust business cases and procurement routes to help Enfield compare the different delivery models.

Key technologies considered included:

• solar PV
• battery storage
• heat pumps
• fabric measures such as external wall insulation
• window upgrades.

Measure packages varied by stock type, planned works, roof suitability and financial viability.

Zero Carbon Accelerator support

The project included three work packages: 

1. ‘One to many’ market analysis and development of templates and tools

The team analysed financed approaches to installing energy systems in council housing. It also developed templates and tools to help London boroughs and social housing organisations choose the most suitable approach for their homes.  

2. Enfield case study  

The team supported Enfield Council to identify and procure an on-balance-sheet solution for solar PV and battery storage across low-rise flats and houses. It ensured the work complemented Enfield’s Social Housing Fund application. 

3. ‘One to many’ roll-out to other users 

The team supported London boroughs to create portfolios of investable projects using the outputs from the earlier work packages. These included approval documents, business cases and decision-making tools.   

The Zero Carbon Accelerator produced a set of practical outputs for Enfield council, including:

• programme business cases
• contractor prospectuses
• Excel programme exports
• a procurement decision tool.

The contractor prospectuses were prepared without capex figures. This allowed the market to price against the technical requirements rather than being anchored to internal estimates.

These outputs helped Enfield Council to move from analysis to delivery. The council used them for internal decision-making, market engagement and procurement preparation, which supported the procurement of an initial pilot project.

The tools enable:

• property-by-property and block-by-block modelling
• live testing of assumptions
• visualisation using street view and overhead imagery
• exportable Excel outputs that Enfield Council can merge into other systems.

The support also helped identify which parts of the stock were most market-ready. Some properties were identified as close to viability under current assumptions. The team separated deeper fabric-first retrofit measures so any additional grant or HRA investment requirements were transparent.

Rafe Bertram, Asset, Retrofit and Sustainability Manager at Enfield Council, said:

“As a result of the business case and procurement work with the Zero Carbon Accelerator team, we procured an Energy Services Partner and are currently delivering the first solar panel pilot projects and have developed a roll-out programme for both houses and flats.

“The Solar for social housing decision tool that the Zero Carbon Accelerator team provided was excellent. It opens a new way of working on intuitive and iterative business cases on a programme, project and dwelling level. It shows construction and project costs and how the funding side matches compares to this – with grant funding, solar financing and HRA investment calculations. It opens the door to the next step in integrated asset programme planning that is rooted in the financial realities of local authorities.”

Funding opportunities identified

The business case considered how Enfield Council could combine internal funding, grants, planned Decent Homes investment, HRA resources, borrowing and third-party finance to scale delivery.

For houses, the analysis assumed a working grant position of £7,500 per property, aligned with Enfield’s current Warm Homes: Social Housing Fund position. It tested the remaining funding requirements through Public Works Loan Board (PWLB) borrowing and revenue from solar, battery and heat pump operation.

The modelling showed that some packages could be self-financing or close to break even, while deeper fabric-first retrofit still required additional council investment or grant. This helped Enfield to distinguish between market-ready, solar-led packages and those needing further public funding. The main benefits of these packages were compliance, fabric improvement and long-term decarbonisation rather than immediate revenue generation.

Challenges and how they were addressed

The key challenges were:

• insufficient public funding
• constrained landlord budgets
• the need to build a business case that could support large-scale retrofit and net zero investment.

The support addressed these challenges by separating the stock into distinct procurable packages. This made it clear which homes could move quickly through financed solar and which required more public investment.

The deep retrofit fabric-first programme, for example, required additional grant or council investment to break even over 25 years, while the solar-led programmes were more immediately financeable.

Other challenges included:

• tariff uncertainty
• data quality
• the practical complexity of matching technical measures to different house and flat typologies.

The modelling treated tariffs, resident electricity consumption, self-consumption, install costs, grants and borrowing rates as sensitivities rather than fixed answers.

A key data lesson was that wall-type records are critical for fabric retrofit. During tool development, the team reclassified 54 properties. The report recommends targeted street-level or archetype-level surveys before committing to fabric packages.

Lessons learned

There are four key lessons learned from this project:

• Agree plans based on clear assumptions, then improve them as better data becomes available. Early modelling can support approval and procurement decisions, but teams should update the figures when they have access to surveys, tender prices, market offers and real performance data.
• Early engagement with wider stakeholders across organisations is important, particularly finance, asset management, sustainability, legal and procurement teams. This ensures that funding routes, resident charging, asset ownership, risk allocation and procurement constraints are understood before organisations take packages to market.
• There are benefits to delivering retrofit alongside planned works, but teams need to define the operational model and financing approach early to achieve best value. This would enable sharing of costs, for example where re-roofing or other capital works already require scaffolding.
• Tariff income should be treated as a variable rather than a constant, with procurement testing a range of revenue scenarios and clearly allocating tariff risk.

Collaboration

Collaboration was a key part of this work, involving Enfield Council, the Greater London Authority (GLA), Energiesprong UK, Mott MacDonald, Warmer Homes London, other boroughs, housing providers and market participants. This included:

• market analysis carried out with boroughs and housing providers
• co-development of shared tools with local authorities and social housing organisations
• engagement with third-party financiers, suppliers and delivery partners to validate business cases, understand market constraints and shape viable procurement and delivery routes
• collaboration with the GLA, Warmer Homes London and partner boroughs on future procurement frameworks.

Energy and carbon impact of the project

Carbon and energy reductions were not delivered directly as part of this project because the work was focused on strategy, business case development and procurement preparation. However, significant modelled energy generation, EPC improvements and resident savings were identified across the proposed packages. 

Table 1: Example savings / revenue for one home with 4kw peak solar & 5kw battery

Category	Approximate annual savings per home
Resident energy bill saving	£480
Smart Export Guarantee average	£112
Potential grid revenue	£330

Across the solar finance-driven houses programme, 254 homes were modelled with 1,331 kWp of solar PV, 2,500 kWh of battery storage and 89 heat pumps. The modelling indicates average resident savings of £298 per year per household on their energy bill.

For flats, the communal stream modelled 1,971 flats across 116 blocks, 11,226 kWp of PV and 10.10 GWh/year of annual generation. The individual stream modelled 626 flats across 141 blocks, with 4,951 kWp of PV and 4.46 GWh/year of annual generation.

What comes next?

The next stage is to use the business cases, contractor prospectuses, Excel exports and procurement decision tool to support Enfield Council’s internal approvals, market engagement and procurement preparation. This will help progress further retrofit packages towards delivery. Several programmes were identified as market-ready and potentially break-even or close to break-even under current assumptions.

Further work will involve market testing to refine costs, tariffs, finance assumptions, operational models and risk allocation before final approval or contracting. The outputs also provide a basis for future one-to-many roll-out, helping other boroughs and social housing providers to create comparable investment-ready projects.

How could this be applied more widely?

In the longer term, the work is intended to scale beyond a single pilot or borough into a repeatable, London-wide delivery model, using standardised finance, procurement and delivery approaches that can be adopted by multiple social housing providers.

The Enfield Council work demonstrates how the Zero Carbon Accelerator can help convert a complex retrofit ambition into a stable, investable pipeline of low-carbon housing projects, with business cases, decision tools and market-facing prospectuses that other landlords can replicate and adapt.