Solar for depot charging: worth it or not?

Depots are, on paper, ideal for solar: acres of flat roof, open yard space, and a business that uses a lot of power. But there’s a catch that’s specific to charging sites — most vehicles charge overnight, and solar only generates during the day. That mismatch is the whole question. Get it right and solar meaningfully cuts your energy bill; ignore it and you export cheap power by day and buy expensive power by night.

The self-consumption problem

Solar is most valuable when you use the power yourself, on site, as it’s generated — that’s worth your full retail electricity price. Power you export to the grid earns far less. So the key question for a depot isn’t “how much can the roof generate?” but “how much of that generation can we actually use ourselves?” A depot that only charges at night has low daytime demand, and much of the solar would be exported at a poor rate — weakening the case.

When solar pays at a depot

Solar’s case is strongest where there’s genuine daytime electricity demand to soak up the generation. That includes depots with vehicles charging or topping up during the day (mid-shift, opportunity charging, or fleets that operate around the clock), significant building loads (workshops, refrigeration, offices), or — importantly — a battery to store daytime solar for the evening and overnight charging. Pairing solar with storage is what turns a daytime resource into night-time charging power, and it’s often the combination that makes both stack up.

Rooftop or canopy?

Most depots start with rooftop solar — it uses space you already have. Solar canopies over parking or charging bays are more expensive but do double duty: generation plus shelter for vehicles and chargers. Which fits depends on your roof condition, orientation and how much you value the covered space.

Sizing it to the depot, not the roof

The temptation is to fill every square metre. The smarter approach sizes the array to what you can self-consume (directly or via storage), because that’s the power that earns full value. An oversized array that exports most of its output at a low rate is a weaker investment than a right-sized one that you use yourself.

The verdict

Solar isn’t automatically right for a charging depot just because the roof is big — the day/night mismatch matters. It pays best when you have real daytime demand or a battery to store the generation for later. Model your actual load shape against the array’s output (and consider storage alongside it) before committing; solar and charging are a great pairing, but only when they’re designed to meet in the middle.

Note: the current Depot Charging Scheme covers chargepoint and civil costs. On-site solar generation is not confirmed as an eligible cost under the scheme, so weigh it on its own energy economics rather than assuming grant support.