NHS Net Zero Funding Windows: What PSDS Phase 4 Taught

The Public Sector Decarbonisation Scheme rewarded preparation more than merit, and the Phase 4 window showed it. Applications opened on 9 October 2024 and closed on 25 November 2024, a little under seven weeks. A trust that started its evidence work when the window opened had already lost most of that time.

What happened in Phase 4

PSDS Phase 4 took applications from 9 October to 25 November 2024 and is now closed to new applications; awards already made continue to be delivered (gov.uk scheme page). The Salix report of 8 December 2025 counted 383 applications seeking more than £1 billion, of which 245 were approved, covering 207 public sector organisations, with more than £816 million allocated, and describes Phase 4 as the closing round. That is roughly two applications approved for every three received. There is no announced successor, so this article is about what the window teaches, not about when to apply next.

What “ready to submit” means for a funding window

Funding applications for building decarbonisation are evidence packs, not forms. Whatever the scheme, the energy savings calculation has to be defensible, which in practice means:

• A baseline energy model of the building (SBEM is the common tool), not estimates from annual bills
• A solar yield model (PVSyst is the common tool), with the file available for checking
• Twelve months of half-hourly consumption data covering winter heating and summer cooling peaks
• A delivery programme showing the money can be spent within the window, ideally with the procurement route already named

Assembling that pack from a standing start takes weeks to months. Trusts that begin when a window opens are competing with trusts that began the previous summer.

The window that closed this summer

The same logic applied to the 2026/27 Great British Energy round. A further £25 million was offered to eligible NHS trusts through an NHS England process announced around the middle of May 2026; the application window closed on 22 June 2026 and projects have to be finished by 31 March 2027 (HEFMA). A short window and a hard delivery date favour trusts with surveyed roofs, half-hourly data and a named procurement route already in hand. We could not find a published list of awards, so ask your regional Greener NHS lead where the programme stands. The Great British Energy NHS solar tracker lists the rounds and the funded trusts, and the NHS net zero explainer covers the targets behind them.

A preparation calendar that works for any window

1. Now: desk feasibility. Half-hourly data and roof drawings feed a model that sizes the system and tests costs and savings. Green Plan wording on solar is checked.
2. Next: roof and services survey (see the roof survey guide), structural advice and a named procurement route (see the procurement guide).
3. Then: governance. Trust Board and, where required, ICB sight of the scheme, so that a window opening is a signature rather than a first conversation.
4. When a window opens: submit early, because late applications compete for what is left.

The cost of missing a window

A trust that misses a funding window loses a year of savings and a year of carbon reduction against targets that are already dated: The NHS has two net zero targets (NHS England, Greener NHS): net zero by 2040 for the emissions it controls directly (the NHS Carbon Footprint), with an 80% reduction between 2028 and 2032, and net zero by 2045 for the emissions it can influence (the NHS Carbon Footprint Plus), with an ambition of an 80% reduction between 2036 and 2039. We could not confirm that any Salix loan route is currently open to NHS trusts in England, so ask Salix whether one is open to your trust before you put one in a business case. Trust capital and a power purchase agreement keep a programme alive between windows; neither is a grant.

The practical conclusion is unglamorous: hospital solar is won in the preparation months, not in the application window. The funding page lists the current routes, and the comparison article on PSDS and Great British Energy shows how they differ.