Wales has one of the oldest and least energy-efficient housing stocks in the UK. A large proportion of that stock is in social ownership — managed by local authorities and housing associations who understand their tenants' needs, but who have rarely had the funding, coordination, or technical infrastructure to deliver retrofit at meaningful scale.
The Optimised Retrofit Programme (ORP) was established to change that. Sero was appointed to manage it — and our role was central to its creation, shape, and growth: designing the programme's approach to outcomes, assembling the partner network, and ensuring that the investment Wales was committing translated into genuinely measurable improvement in people's homes and lives.
What the Optimised Retrofit Programme is
The ORP was not a conventional grant programme. It was designed from the outset around learning and evidence — treating the first phase of delivery not just as improvement works, but as a data-gathering exercise that would inform how subsequent investment was targeted and sequenced.
Sero's role as programme manager brought together 68 partner organisations across Wales, including 26 social housing providers. The initial programme targeted over 1,700 homes, with £13 million of foundational funding from Welsh Government and a remit to build the case — in real, measured outcomes — for the much larger investment the sector needed.
The ambition was always to demonstrate that social housing retrofit, done properly, could deliver genuine improvements in warmth, health, energy costs, and carbon emissions — and that those improvements could be verified independently, not just asserted.
The scale of the challenge
Since 2020, Welsh Government has committed over £466 million to home energy efficiency programmes. Across Wales, 31,000 or more energy efficiency upgrades have been completed. These are significant numbers — but the total cost of bringing the Welsh social housing stock to the standard required for net zero has been estimated at £5.52 billion over ten years.
The gap between what has been invested and what is needed is stark. Research by CIH Cymru has identified a 75% funding shortfall — a structural challenge that cannot be resolved by incremental increases in public spending alone. The ORP's evidence base, built through Sero's management of the programme, is part of the case for unlocking the private and institutional investment that must ultimately bridge that gap.
The insight that drove our approach to the ORP was simple but consequential: the barriers to social housing retrofit are not primarily technical. They are financial, organisational, and evidential. Our job was to address all three — not just to install measures, but to build the infrastructure that makes retrofit fundable, repeatable, and provable.
Outcomes, not just outputs
The distinction matters enormously in retrofit. The sector has a long history of claiming improvements that are never independently verified — of counting measures installed rather than measuring warmth delivered or bills reduced. The ORP was designed differently: with monitoring built in, with independent assessment of outcomes, and with a commitment to publishing what was actually found rather than only what was planned.
This outcomes-led approach was not without friction. It required housing providers, contractors, and funders to accept a degree of transparency that the industry has not traditionally welcomed. But it is the only basis on which retrofit at scale can be justified to the public, to tenants, and to the institutional investors whose capital the sector ultimately needs.
"In 2026, we need to stop debating and start delivering. The evidence is there. The technology works. What's missing is the will to organise finance at the scale the challenge demands."
Andrew Sutton, Co-Founder & Chief Innovation Officer, Sero
What comes next
The ORP has established that coordinated, outcomes-led social housing retrofit is achievable in Wales. The question now is whether the financial and political infrastructure can be built to take it to the scale the housing stock demands.
Sero continues to work with Welsh Government, housing associations, and financial institutions to develop the models — blended finance, green bonds, pay-as-you-save mechanisms — that could unlock the investment needed to close the gap between what has been done and what needs to be done. The ORP is the proof of concept. The next decade is the delivery challenge.