Fleet Depot Charging with Solar: Design, Cost and Grants

Start from the rota: energy and power for 20 vans

Twenty electric vans do not need twenty chargers running at full power. They need a schedule. The arithmetic below uses a van energy figure of 0.40 kWh a mile — an illustration, not a published figure, so substitute your own vehicles’ data — and 18,000 miles a year over about 261 working days.

• Each van drives about 69 miles on a working day and needs about 27.6 kWh to replace it.
• Twenty vans need about 552 kWh a working day, or 144,000 kWh a year — an average draw of only 16 kW across the whole year.
• Delivered over a 12-hour overnight window, that is an average of about 46 kW. If every van charged at the full 7 kW of its socket at the same moment, the depot would see 140 kW.

The gap between 46 kW and 140 kW is why load management exists: a controller shares the available capacity across the sockets and holds total demand under the supply limit, so a depot’s socket count is not set by nameplate arithmetic. A last-mile fleet with staggered returns can need fewer sockets than vans; a single-shift fleet parked from evening to morning has a long window and needs little power per van. Socket choice and hardware follow the charger guide, at fleet duty-cycle grade.

Supply capacity: measure, manage, then upgrade

Depot supplies were sized for lighting, conveyors and a kettle, not for fuel delivered electrically. The sensible order is to measure the real half-hourly headroom; fit charging inside it with dynamic load management; consider storage where an unavoidable peak justifies it; and only then ask the network operator for more capacity. A combined solar-and-charging project can put generation and new demand to the DNO together, and the grid connection guide sets out how the G99 application for the array and the DNO’s process for the chargers fit together.

What the vans cost to run: public chargers, depot grid power, depot with solar

For the same 20 vans, 18,000 miles each, the yearly cost of the energy depends on where it is bought. The solar rows use a 100 kW array in London (90,430 kWh a year, 0.63 times the vans’ yearly demand) with each solar kWh counted at the array’s lifetime capital cost of 5.5p a kWh.

Assumptions: public prices are Zapmap’s August 2026 pay-as-you-go averages (54p standard, 77p rapid); depot grid power is the DESNZ Q1 2026 average non-domestic price including CCL (24.14p); the array costs £1,167 a kW (DESNZ 2025/26 non-domestic 10–50 kW mean) and degrades 0.5% a year over 25 years; van energy use 0.40 kWh a mile is illustrative; weekdays only; no building load, no battery.

Two things stand out. Moving the vans from public rapid chargers onto the depot’s own supply cuts the cost of their energy by about 69% (and by 55% against public standard chargers) before any solar is involved — for a depot whose vans currently rely on public charging, that is the larger saving. And the array’s value depends heavily on when the vans are parked, which the next section explains. Run your own vehicles through the EV charging cost calculator.

How much of a depot’s charging can solar cover?

An hour-by-hour model using PVGIS data for 2005–2023 answers this for a given parking pattern (the method and its limits are on the calculator page). Vans parked at the depot from 10:00 to 16:00 on weekdays, with chargers that follow the sun, took 31% of their energy from the 100 kW array above. The same vans with chargers that simply start at full power on arrival took 24%. Vans parked only overnight, from 18:00 to 07:00, took 2%, because only about 3% of an array’s yearly output falls inside an evening-to-morning window.

That last figure corrects a common claim. Without a battery, an overnight depot gets almost no direct benefit from rooftop solar; the array’s value then comes from the building’s own load and from exports. For depots where vans do sit in the yard during the day — between delivery waves, on shorter shifts, or at weekends — solar-following control is worth specifying from the start, and where the roof is shaded or full, solar canopies over the yard can add array capacity. How the control layer works is set out in the solar EV charging guide.

Van scale, mixed scale and HGV scale

Vans. Mature vehicles and slow AC charging suit long parking windows, and the saving is driven by getting vehicles off public chargers. Mixed fleets. Adding a faster AC socket or a DC unit for mid-shift turnarounds raises the peak, so load management becomes essential as more vehicles charge at once. Heavy goods vehicles. Electric HGVs need much higher charging power per bay than vans, which is likely to mean dedicated supply works and, at scale, the depot’s own high-voltage assets. A depot that ducts and provisions for that at the van stage can usually add the next phase more cheaply than one that has to reopen a finished yard. Do not specify HGV charging from a rule of thumb; ask the vehicle manufacturer for charge power and the DNO for the supply position.

Grants for depot charging

The Depot Charging Scheme offered to fund 70% of charge point and civil costs, up to £1 million across all sites, in its first window (25 March to 30 June 2026). A second window is expected to open on 28 October 2026 and close on 29 January 2027, with terms and rates still to be confirmed. The scheme does not mention grid upgrades, solar or batteries as eligible costs, and applicants agree not to obtain similar Government funding for the funded activities, so check how it interacts with the Workplace Charging Scheme before applying for both. The page on the scheme sets out who qualifies, and the round 2 preparation checklist covers what to have ready.

For the solar side, the Annual Investment Allowance gives 100% relief on up to £1 million of plant a year, and new chargepoints take a 100% first-year allowance until 31 March 2027 for companies — see the capital allowances guide. The wider case for combining the two is on the EV charging business case page, and the same logic scales down to commercial solar EV charging at smaller workplace sites.

What a finished depot reports

A well-run combined depot should report three numbers each month without being asked: the share of vehicle energy that came from solar, the pence per mile by vehicle, and peak demand against the supply limit. Those are the figures that show whether the design delivered what the model promised. If they are not on the handover pack, ask for them. A good place to start the conversation is a combined desk feasibility built from twelve months of half-hourly data and the vehicle rota — the quote form below asks for the few facts it needs.

Sources

• GOV.UK Find a Grant — Depot Charging Scheme (read 14 October 2026).
• Zapmap Price Index, August 2026 — zapmap.com.
• DESNZ Quarterly Energy Prices, table 3.4.2 (Q1 2026); DESNZ Solar PV cost data 2025/26.
• EU JRC PVGIS 5.3 hourly series (SARAH3, ERA5), 2005–2023.
• HM Treasury, first-year allowances for chargepoints (26 November 2025); GOV.UK Annual Investment Allowance.

Checked 14 October 2026. The 20-van example uses stated assumptions and is an illustration, not a quotation.