HTM 06-01 and Rooftop Solar: What NHS Estates Teams Need to Know

Most solar articles aimed at hospitals stop at the funding: how a grant scheme pays for the panels, what the payback looks like, how many tonnes of carbon come off the estate. Almost none explain the part that decides whether an install can proceed on a live acute site: HTM compliance. For NHS estates teams, HTM 06-01 solar is not a marketing phrase. It is the electrical-services standard that any rooftop PV system tying into a hospital's supply has to satisfy, and it sits alongside a stack of other Health Technical Memoranda that govern how contractors behave inside a working hospital. This article is written for the estates and facilities professionals who have to sign the work off, and it explains where HTM 06-01 and its siblings bite during a solar project.

HTM 06-01 at a glance

HTM 06-01 is NHS England's Health Technical Memorandum on electrical services supply and distribution: guidance on the design, installation and testing of fixed wiring and integral electrical equipment, covering the electrical infrastructure within healthcare premises. It is written for healthcare managers, electrical safety groups, design engineers, estate and operations managers and contractors, to be read alongside BS 7671, and it applies to new and existing sites. It was first published on 1 February 2007; NHS England's publication page was last updated on 26 January 2024 and gives 11 April 2017 as the document's last update. The page does not address generation or secondary supply, so the detail on those points sits in the full 183-page document: read the current edition before writing a specification.

What HTM 06-01 covers, and why solar touches it

HTM 06-01 is the Health Technical Memorandum for electrical services supply and distribution in healthcare premises. It is the framework the NHS uses to keep the electrical infrastructure behind theatres, imaging, intensive care and ventilation safe, resilient and properly documented. A rooftop solar array is not a bolt-on appliance — it connects into the hospital's distribution system, and the moment it does, it falls inside the world HTM 06-01 governs. That is why hospital solar compliance is a genuinely different discipline from commercial rooftop work: the array, its inverters, its isolation and its metering all have to be designed, installed and verified to a standard written for premises where an unplanned outage is a clinical risk, not just a nuisance.

The practical consequence is that competent installation is not enough on its own. The system has to be integrated in a way an Authorising Engineer (Electrical), the AE(E), can review and authorise against HTM 06-01. If your prospective contractor cannot tell you how their design will be verified against HTM 06-01 and who provides the AE(E) review, that is the answer to whether they have worked on a hospital before.

The full compliance stack on a live hospital site

HTM 06-01 is the electrical piece, but a rooftop install on a working hospital sits inside a wider set of standards. Estates teams should expect a competent contractor to speak to all of the following, not just the one on the tin:

• HTM 06-01 (electrical services) — the design, installation and verification standard for the PV connection into the hospital distribution system, with AE(E) review.
• HTM 03-01 (infection control in the built environment) — governs how construction work is carried out where patients are present, including immunocompromised zones. Contractors are inducted by Estates and IPC teams, construction zones are segregated from clinical areas, and negative-pressure zones are maintained where applicable.
• DBS clearance for contractors in patient areas — trusts typically expect Enhanced DBS plus the relevant Barred Lists for anyone accessing patient zones. Mental health sites require additional safeguarding awareness; children's hospitals require Children's Barred List checks.
• G99 DNO connection — the grid connection application required above 16 A per phase (about 3.68 kW on a single phase), submitted to the Distribution Network Operator before energisation.
• AE(E) review, CQC continuity and Greener NHS Green Plan alignment — the electrical authorisation, uninterrupted care standards, and the estate's decarbonisation strategy the scheme should map to.

None of these are exotic. They are the everyday realities of building on an NHS estate, and a contractor who has genuinely delivered for NHS Trusts will talk about them without prompting. A contractor who cannot has, at best, done commercial rooftops and assumed a hospital is the same job.

HTM 03-01: keeping infection control intact while the roof is worked on

The objection estates teams raise most often is not cost — it is continuity. How do you install solar on a building where operating theatres, wards and intensive care cannot pause, and where immunocompromised patients cannot be exposed to construction dust? HTM 03-01 is the answer, and it is why the sequencing of a hospital install looks nothing like a warehouse.

Roof installation happens above operational areas with essentially no impact on the clinical space beneath. Theatres, wards and ITU continue normally. Contractors work to HTM 03-01 protocols throughout — inducted by the Estates and infection prevention and control teams, construction routes segregated from clinical circulation, and PPE and dust-control measures applied. The only point at which the work reaches into the building is the final grid connection: a short, planned electrical outage of roughly four to eight hours, scheduled with Trust Estates and theatre management for a maintenance window. Done properly, an acute-hospital array can be installed during normal operations, which is exactly why HTM 03-01 competence matters more than raw installation speed.

AE(E) review and the medical-equipment question

A concern that surfaces on almost every hospital scheme is whether solar could interfere with sensitive medical equipment. It is a fair question, and the technical answer is reassuring: modern grid-tied PV inverters comply with EN 50549 and produce a clean sine-wave output that is indistinguishable from the grid supply. Installed by competent contractors and verified to HTM 06-01, there is no interaction with sensitive equipment. This is what the AE(E) review exists to confirm: that the electrical design and its EMC behaviour have been reviewed by a qualified authorising engineer before the system is allowed to energise. Estates teams should treat the presence or absence of a credible AE(E) route as the clearest signal of whether a contractor understands hospital work.

G99 and grid connection on a hospital estate

Generation above 16 A per phase (about 3.68 kW on a single phase) needs a G99 application to the local Distribution Network Operator and DNO approval before it can be energised; smaller systems use the G98 connect-and-notify route (ENA EREC G98/G99). On many commercial sites the DNO process is the long pole in the tent. Hospital sites are often less constrained, because acute hospitals typically hold very large existing grid connections and a PV connection is usually additive rather than requiring reinforcement. That does not remove the G99 step, but it does mean the connection is rarely the reason a hospital scheme stalls. A contractor who folds the G99 application into the programme from day one keeps the whole project on its timeline.

What estates teams should actually ask a contractor

If you take one practical thing from this, make it a short list of questions to put to any solar contractor bidding for hospital work. Ask how their design will be verified against HTM 06-01 and who provides the AE(E) review. Ask how they work to HTM 03-01 during the roof install and how they sequence the final grid connection around theatre schedules. Ask whether their entire on-site workforce holds Enhanced DBS clearance for patient areas. Ask when they will lodge the G99 application. The answers separate genuine healthcare-estate contractors from commercial installers who have never worked on a live acute site.

Getting HTM 06-01 solar right is not a compliance tax bolted onto a good idea. It is the difference between a scheme that clears governance and energises on schedule and one that stalls at the first estates review. The standards exist because hospitals cannot tolerate electrical surprises, and a well-run rooftop project treats them as the design brief rather than an obstacle. For the wider picture on funding, sizing and delivery, see the page for NHS trust estates teams and the hospital solar homepage; to talk through your own site, send an enquiry and we reply by email.