SOLAR PV
Design There is a moment in most projects where somebody asks: ‘can we just fill the roof?’ Sometimes you can. Often you should not. The largest value of solar comes from consuming
the electricity on site. Exporting back to the grid via the Smart Export Guarantee (SEG) brings a return, but it is materially lower than the value of avoided grid purchases – 10-15p per kWh compared to the 25+p per kWh Trusts are often paying for grid electricity. A system that generates more than the site can use sounds efficient; financially, it rarely is. Matching generation to actual demand, using real half-hourly energy data makes for a more cost-effective system.
Planning Solar PV on the roof is usually covered under permitted development, and does not require full planning permission. However, in some cases planning permission is required, including if the building is listed, or if your solar is ground mounted.
Engage your local authority early in the process to find out what is likely to be accepted. Working with an installer can be useful here as they may be able assist with the planning application by producing a design with non-penetrative mounting systems, or one that aesthetically matches the existing rooftop.
Inverter selection String inverters connect panels in series. They are cheaper than microinverters and work well on simple, unshaded roofs. The limitation is that if one panel in a string is shaded, the entire string’s output drops to the weakest panel’s level. Microinverters are mounted on each individual panel and optimise output independently. They cost more per panel but eliminate shading losses, provide panel-level monitoring, and carry a significantly longer warranty: 20–25 years, compared to 10–12 years for string inverters. On complex NHS roofscapes with significant plant and obstruction, the performance gain from microinverters will typically offset the additional cost over the system’s life.
Healthcare-specific design requirements NHS sites carry design requirements that do not appear on commercial or industrial projects. Fire safety systems must be integrated with the site’s firefighter switches, which are disconnection devices that allow the fire service to isolate the array safely. This should be coordinated with the Trust’s fire safety officer from the outset. Sites with operational helipads require careful consideration of panel orientation and anti-glare treatment to avoid reflected sunlight creating a hazard for pilots. This is a soluble problem, but it must be addressed at design stage, not discovered during CAA consultation after installation.
What to give your designer Design works best when it is fed with real information. The following should be assembled before design begins: n Half-hourly electricity usage data. n Roof structural drawings. n Roof orientation, dimensions, and shading survey. n Roof material and condition report. n DNO correspondence. n Helipad location and operational windows. n Available space for inverters and associated equipment.
East Surrey Hospital.
October 2026 Health Estate Journal 115
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