The Hospital Solar Process, Step by Step
Most of a hospital solar project is governance, funding and procurement time, with a comparatively short roof installation. Knowing where the time goes is how estates teams keep projects on programme.
Where the time actually goes
The physical installation of a large hospital array is a matter of weeks to a few months. Everything else is process: the funding route, framework procurement, grid approval under G99, and the trust's own governance calendar. None of these steps can be skipped, but they can be overlapped, and overlapping them well is most of what good project management contributes before anyone touches the roof. Generation above 16 A per phase (about 3.68 kW on a single phase) needs a G99 application and DNO approval before connection; smaller systems use the G98 connect-and-notify route (ENA EREC G98/G99).
Five stages from data to generation
- 01Stage 1
Desk feasibility
A desk feasibility starts from 12 months of half-hourly data and roof drawings. The array is modelled against the real load profile, the roof is screened from drawings and aerial survey, and the output is a system size, installed cost, savings, CO2 impact and recommended funding route, with no site visit needed.
- 02Stage 2
Funding & business case
The funding route is chosen and the Full Business Case is assembled with HM Treasury Green Book treatment for Trust Board sign-off. With PSDS closed to new applications, that means Great British Energy or trust capital for NHS bodies; private groups get capital, finance and PPA options modelled side by side.
- 03Stage 3
Design & approvals
A structural engineer verifies roof loading (see the roof survey guide), the HTM 06-01 electrical design goes through Authorising Engineer (Electrical) review, and the G99 application is lodged with the DNO. In England, rooftop solar on a non-domestic building is permitted development under Part 14 Class J: up to 50 kW counts as microgeneration, and larger roof arrays need the local planning authority's prior approval of design and appearance, including glare. It is not permitted on a listed building or within its curtilage, and limits apply to height above the roof and distance from the roof edge. Wales (Part 43 Class A) and Scotland (Class 6J) have their own rules, so check the current order with the council. The infection-control methodology is agreed with the IPC team.
- 04Stage 4
Installation
Mobilisation with Estates and IPC induction, DBS verification and segregated work zones. Roof installation proceeds above live clinical operations, with wards, theatres and ITU running normally. Weekly programme reviews with the Estates team, and crane lifts and deliveries scheduled around clinical activity and helipad operations.
- 05Stage 5
Connection & handover
Expect a single planned window for the grid connection, agreed with Estates and theatre management weeks in advance, followed by commissioning, EN 50549 compliance verification, monitoring that feeds the BMS, O&M documentation and operator training.
What never gets interrupted
Clinical operations. Work on a live hospital site is expected to follow HTM 03-01 infection-control practice: contractor induction by the Estates and infection-prevention teams, segregated construction zones, and maintained negative-pressure areas where they apply. Wards, theatres and ITU normally keep running during roof work; the usual operational touchpoint is the final grid connection, which is planned with Estates and theatre management as a scheduled window. The grid connection window is the only planned outage event, and it is scheduled like any other piece of estates maintenance: agreed weeks ahead, with theatre lists protected.
After commissioning
A long-lived asset needs more than a handover pack. A good handover includes monitoring from day one with fault alerts to the trust's helpdesk, generation data that feeds ERIC returns and Green Plan reporting for NHS sites (and ESG disclosures for private groups), a published O&M schedule for panel cleaning and inverter maintenance, and an annual review of performance against the yield model. The yield file should be shared at proposal stage and be verifiable by any third party.
Ready to start the clock?
Stage one needs nothing from the estate but data: half-hourly consumption and roof drawings. If your project depends on funding, check the current funding routes early, since application windows drive the whole programme; the article on application timing explains what the Phase 4 window showed about preparation. To talk through your own site, send an enquiry and we reply by email.