Last-Mile Depots: Solar panels for distribution centres

Why a last-mile depot pairs solar and EV charging better than any other site

The last-mile depot is the building where solar and electrification meet most neatly. These sites exist to dispatch and recover delivery vehicles, and as those fleets shift to electric vans the daytime demand for charging power climbs steeply, just as the panels overhead are at their most productive. Vans that load and depart in the morning and return through the afternoon can be topped up from on-site solar at high self-consumption, turning the roof into a fuel source for the fleet. That synergy is the reason a last-mile depot is such a strong solar case even at a smaller scale than a full distribution centre, with a strategic value that goes well beyond the electricity bill.

Last-mile is also where the national parcel and post operators are pushing hardest on decarbonisation, and many depots form part of programme-level rollouts across a carrier's estate. That means a solar and charging scheme at one depot is often a template for many, and the customer pressure that runs through every parcel network rewards operators who can show clean, self-generated power feeding an electrifying fleet. For an operator standardising depots across the country, getting the solar and charging design right once and repeating it is a meaningful prize, because the design effort amortises across the whole programme rather than being repeated site by site.

The economics also read slightly differently from a large warehouse. A last-mile depot is a smaller building, so the absolute capital is lower and the decision is easier to take quickly, but the strategic value of pairing solar with fleet charging is disproportionately high. Every electric van charged from the roof is a van not drawing from the grid at the grid price, and network charges apply to depot charging just as they do to any other import. Solar turns a rising fleet-charging cost into a largely fixed one, which is exactly the kind of certainty a depot manager planning a multi-year EV transition is looking for.

What a typical install looks like and how it is sized

Array size depends on usable roof area, structural capacity, the daytime load and the grid connection; PVGIS gives roughly 886 to 1,042 kWh per kWp per year across the cities we have checked, so annual generation is about that figure multiplied by the kWp the roof can take. Sizing on a last-mile depot is driven by two loads that increasingly merge: the building baseload of lighting, sortation and welfare, and the EV charging demand of the van fleet. Because daytime charging absorbs solar at almost full self-consumption, the array should be sized around the charging profile as much as the building.

The EV charging infrastructure should be designed alongside the PV rather than as an afterthought, because the two share a grid connection and have to be planned as one system. Solar and charge points should be modelled together from half-hourly data so generation and charging line up through the working day. The art is in the timing: vans that depart in the morning and return through the afternoon present a charging window that overlaps the solar peak, so a well-designed depot can charge a large share of its fleet directly from the roof. Where the return pattern is concentrated into the evening, assess whether a battery bridges the gap between midday generation and evening charging demand.

Costs, payback and tax relief

Payback depends on the installed cost and on how much of the output is used on site, so compare written quotes and ask for the assumptions behind any figure; the cost guide sets out the method. Because the building is smaller than a full distribution centre, the absolute capital is modest and the decision is one a depot manager or regional head can often take without a lengthy board process, which is part of why last-mile solar moves quickly once a programme is agreed. Capital allowances help within the limits set out in the grants guide. Solar PV is plant and machinery and is normally special-rate plant, so the Annual Investment Allowance covers the first £1m a year of qualifying spend (a limit shared with other plant spend and associated companies), spend above it attracts a 50% first-year allowance, and full expensing does not apply. Where the fleet charges through the day, almost all generation is self-consumed, but on quieter days the Smart Export Guarantee pays for any surplus. Our cost guide sets out how to read a quote.

Funding routes in detail

Last-mile depots are frequently leased urban sites, so funding usually pairs a capital or finance route with a lease solution. Owner-operators usually buy outright or via asset finance and claim capital allowances: the Annual Investment Allowance up to its £1m a year limit, then a 50% first-year allowance, so a project above £1m is not written off in one year. Tenants more often use a Power Purchase Agreement, which removes the capex and suits the shorter or programme-driven leases common in last-mile, with the lease itself enabled through the Green Lease Clause and Tenant Capital Recovery route and the Better Buildings Partnership toolkit addendum.

Because depots are so often delivered as part of a national programme, the funding decision is frequently taken once at estate level and then applied across many sites, and proposals can be structured to support that, with consistent assumptions a head office can compare and approve in one go. A site inside a designated Freeport or Investment Zone tax site may claim a 100% first-year allowance on new, unused plant used primarily in the site, with end dates set by HMRC, so check the site against the official designation before relying on it. The Smart Export Guarantee pays a supplier-set tariff on surplus, which matters on lighter days when the fleet is out and the building load alone is small. The funding guide sets out each option and how they combine with the charging spend.

Compliance and sector considerations

The compliance picture for last-mile is shaped by its urban setting and its charging element. Urban planning is more involved than for a rural distribution centre, so local planning should be factored into the programme rather than assuming Permitted Development will cover everything, although Class J of Part 14 of the GPDO 2015 still applies to much of the rooftop PV. The EV charging infrastructure has to be designed alongside the PV, with the grid connection sized for the combined load, which is exactly why solar and charging should be treated as one scheme rather than two projects sharing a roof.

The standard logistics framework still applies: LPC sprinkler clearances where present, with the array laid around the heads; insurer pre-design sign-off before fabrication, since the same insurer review applies to depots as to large sheds; wind loading to BS EN 1991-1-4 for the site exposure; and a G99 grid application above 16 A (3.68 kW) per phase. Where fire detection is integrated, BS 5839-1 applies. On a smaller urban roof the grid connection capacity is often the item to confirm earliest, because the combined PV-plus-charging load can be significant relative to the building's existing supply, and it is better established at the survey than discovered late.

How to approach this kind of project

A last-mile depot should be treated as a combined solar and charging project from day one, because that is how the building actually works. Start with half-hourly meter data and the planned EV charging profile so the array, the charge points and the grid connection are sized as one system rather than three separate decisions that fail to add up. The urban planning position should be addressed early, the structural and roof checks run before a layout is fixed, and the sprinkler and insurer position resolved in parallel.

The G99 application is best submitted at the survey stage so the connection process for the combined load is underway from the outset, which on an urban site with limited spare capacity is often the deciding factor in the timeline. A good proposal is fixed-price and covers both the PV and the charging infrastructure, the workmanship should carry an insurance-backed warranty, and where the depot is one of many the scheme should be designed to be repeatable across the estate so the carrier's programme team has a template rather than a one-off. Installation happens above the operation so van loading and despatch continue, with only the final grid connection needing a scheduled window. The result is a depot that fuels its own fleet from its own roof, designed once and ready to repeat.

If your network also includes larger ambient or automated sites, see distribution centre solar and fulfilment centre solar. When you are ready, request a quote from your meter data, see the cost guide or read the depot solar FAQs first.