Commercial solar for London buildings

Every London postcode sits in the London Power Networks licence area, one of the three networks operated by UK Power Networks. They are the party who approve your connection, not your electricity supplier, and confusing the two is the most common reason a project stalls at the paperwork stage.

Small installations are notified after the event under the G98 process. Anything larger, which covers essentially every commercial array, needs an application under G99 and approval before energisation. UK Power Networks publish their application routes and typical determination times, and the sensible move is to submit early, because the answer occasionally shapes the design.

Where central London supplies are already close to their firm capacity, an export limitation device is often the pragmatic answer. Limiting or preventing export costs a London site very little, because a building consuming through the working day exports almost nothing anyway.

The defining constraint is plant. Air handling units, chillers, lift overruns, riser heads, window cleaning tracks and safety zones routinely take half of the plan area of a city centre office roof, and the remaining space is broken into awkward parcels rather than one clean rectangle.

That is why a gross roof measurement taken from a satellite image is close to useless here. An outline traced honestly around the clear space, then reduced for maintenance access to the plant, gives a much smaller number and a far more credible one.

Older converted stock behaves differently again. Warehouse and industrial conversions across the inner east and south have pitched or lightly framed roofs where the structural check matters more than the space, and mansard and set back roofs on period buildings often have no viable plane at all.

Solar on a commercial roof is frequently permitted development, but that permission is narrowed or removed on listed buildings, in conservation areas and where the array would be visible from the street or from a protected view. London has more of all of these than anywhere else, and every borough interprets its own policy.

The practical test is visibility. A flush or low tilt array set back behind a parapet on a flat roof rarely raises an objection. A tilted array on a visible pitched roof in a conservation area is a genuine planning question and should be treated as one before design work begins.

Overshading from neighbouring buildings deserves the same early attention. In dense areas a tall neighbour can remove a meaningful part of the winter yield, which a shading study picks up and a rule of thumb does not.

The dominant commercial building types here are offices, managed multi let estates and retail, with logistics concentrated at the edges around the orbital motorway rather than inside the city. Load in those buildings is weekday, daytime and closely aligned to generation, which is exactly the profile that makes self consumption high.

The complication is tenure. Landlord and tenant structures decide who can install, who takes the benefit and how the generation is metered, and this needs resolving before design rather than after. Common routes are landlord ownership serving the landlord supply, or generation recovered through the service charge.

Weekend generation is the honest weakness of a five day office. It exports, at a lower value than it saves, which is one of the stronger arguments in London for pairing a modest array with storage or with electric vehicle charging in the car park where one exists.

We do not have a London office and we are not the installer. NRG Solar assesses the site, models the numbers and matches you with a vetted installer who works in the capital and understands its access, out of hours and permit requirements.

That matters more here than elsewhere. Roof access in central London can mean a crane licence, a road closure, restricted delivery windows and building management approval, and an installer who has never worked inside the congestion charge zone will underprice all of it.

The assessment is free, produces indicative figures using our published assumptions, and comes with no obligation. If the honest answer is that your roof is too small or too crowded to justify a project, we will tell you that instead.