Last-Mile Depots: Solar panels for cold storage

Why a last-mile depot is a smart, fast-moving solar site

Last-mile depots are smaller than the big sheds, but they suit solar very well, and they matter to anyone thinking about solar panels for cold storage because so many last-mile operations now move chilled and frozen goods and run refrigerated vans and loading areas from the depot. The standout feature of a last-mile site is the EV van fleet. As fleets electrify, daytime van charging creates a perfect synergy with rooftop generation: the vans charge while the sun is up, absorbing solar at close to 100% self-consumption. Add any on-site chilled storage or refrigerated loading, and the daytime baseload climbs further. Self-consumption is the single biggest driver of solar payback, and the charge-while-you-generate pattern of a last-mile depot captures it efficiently, giving a typical simple payback of around 5.5 years.

These depots are often part of national programmes such as Royal Mail, Evri and DPD, where sustainability commitments and electrified fleets are rolled out across the estate. On-site solar supports those commitments with auditable Scope 2 reduction and helps insulate the depot from network charges, which have risen 40 to 80 percent since 2022 and hit every site in the network. For an operator running many depots, a repeatable solar-plus-charging design across the portfolio is an attractive, scalable way to cut cost and emissions at the same time, and the smaller capex per site makes the programme easier to phase. The depot is also where the chilled last mile begins, so even a modest array offsetting refrigerated loading and van pre-cooling earns its keep.

The economics also benefit from the fact that what the panels make on a depot tends to be used the moment it is generated. A van plugged in at midday is a near-perfect match for the solar peak, absorbing the output at close to 100% self-consumption with no export at the lower rate. As more of the fleet electrifies, that daytime charging demand grows, and a depot that has already installed solar finds the array becoming more valuable over time rather than less. For chilled depots the refrigerated loading and van pre-cooling sit underneath that charging demand as a steady floor, so the self-consumption case is robust even before the fleet is fully electric. This is why we treat the fleet electrification plan, not just the current load, as a core input to the depot design.

What a typical install looks like and how we size it

For a last-mile depot we usually design a system in the 100 to 400 kW range, which is roughly 185 to 740 panels across about 600 to 2,400 square metres of roof. A system that size generates in the region of 92,000 to 370,000 kWh a year and saves somewhere between 21 and 85 tonnes of CO2 annually. Sizing on a depot is driven by the daytime load and DNO capacity, and the EV charging schedule is central to it: a typical depot install pairs 100 to 400 kW of PV with 6 to 24 charge points so that the vans absorb solar directly during the day.

We pull the half-hourly meter data and the fleet charging profile together, then design the system and the charging infrastructure as one, so daytime generation goes into the vans and any chilled storage rather than to export at a lower price. The charging pattern of a last-mile fleet often aligns well with the solar curve, because vans return to depot through the afternoon and charge into the evening, and a battery can extend midday generation into that early-evening charging window where the economics support it. Because these are urban sites, we also check the realistic usable roof area once rooflights, plant and any shading from neighbouring buildings are allowed for, so the quoted system is one the roof can actually carry. The aim is a depot that runs its electrified fleet and chilled loading substantially on its own solar.

Sizing a depot is therefore as much about the charging schedule as the roof. A depot with a large overnight charging window and few vans plugged in during daylight will self-consume less of its solar than one that tops up vehicles through the day, and the right answer for each site comes out of the half-hourly data and the fleet rota rather than a rule of thumb. Where the charging is mostly overnight, a battery to store midday generation for the evening and overnight window can lift the economics considerably, and we model that explicitly. The number of charge points, between roughly 6 and 24 on a typical depot of this size, is chosen alongside the array so the incoming supply, the PV and the chargers are all sized as one coherent system rather than three separate projects bolted together.

Costs, payback and tax relief

A last-mile depot project typically lands between £90,000 and £340,000 depending on system size, at roughly £700 to £900 per kW. Simple payback sits near 5.5 years, and the electricity is effectively free for the system's long life after that. The headline relief is tax: solar PV qualifies as plant and machinery, so the 100% Annual Investment Allowance lets a depot install be fully expensed against profit in year one, comfortably within the £1m cap at depot scale, worth up to a quarter of the project value back as tax for a limited company.

Because much of the generation goes straight into the van fleet and any chilled load, the return is driven by avoided import, which is the strongest position to be in. The Smart Export Guarantee covers any surplus at 4 to 15p per kWh as of 2026, which mainly applies on quieter days when fewer vans are charging. Where charge points and PV are installed together, the whole package is assessed as qualifying plant, which keeps the tax treatment clean. Our cost guide works through depot-scale numbers so a multi-site programme can be budgeted consistently.

Funding routes in detail

The funding picture for a depot follows the same routes as larger logistics sites, scaled to a smaller capex. Capital allowances are the core relief: a depot install is typically fully expensed in year one under the Annual Investment Allowance, and where charge points and PV are installed together the qualifying plant is assessed as a package. If the depot lies within a Freeport or Investment Zone, Enhanced Capital Allowances can deliver effective 100% first-year relief on qualifying plant.

For leased urban depots, the Green Lease Clause and tenant capital recovery route unlocks your ability to install on a building you do not own, and we provide the BBP-aligned lease addendum that most landlords accept; for owner-occupied or family-owned depots consent is usually quick, often one to four weeks. The Smart Export Guarantee adds value for any export. Where the depot is part of a national programme, a single funding and lease template can be replicated across the estate, which is where a PPA can also be attractive because it removes capex from each site. We map the routes that apply to your specific depot, and to your wider network where relevant, during feasibility.

Compliance and sector considerations

The depot-specific consideration is planning. Last-mile depots are smaller, urban sites, so planning can be more involved than for a rural distribution centre, and we factor that into the timeline and the design rather than assuming permitted development will simply apply. The second is EV charging integration: the charging infrastructure must be designed alongside the PV from the start, not bolted on later, so the two work together and the incoming electrical capacity is sized for both the array and the chargers.

The standard logistics regime still applies where relevant: LPC sprinkler clearances (1m to the deflector, 0.6m at high-bay), insurer pre-design review with the major insurers' specific PV criteria, and a G99 grid application above 17 kW per phase. Where chilled storage or refrigerated loading is present on the depot, the F-gas Regulations on that plant continue to apply and we design around them. Wind loading is designed to BS EN 1991-1-4. Most rooftop PV falls under permitted development through Class A Part 14 of the GPDO 2015, but urban siting means we always confirm the local position early, including any conservation or amenity constraints that an inner-city depot might face.

How we approach this kind of project

We design the depot system and the charging infrastructure together, because on a last-mile site they are inseparable. We begin with the half-hourly meter data and the fleet charging profile so the PV is sized for genuine daytime self-consumption into the vans and any chilled load. We complete a roof and structural check with a wind-load assessment to BS EN 1991-1-4, confirm the usable roof area in an urban setting, and check the urban planning position early given the more constrained siting.

We submit the G99 grid application early so the DNO clock runs in parallel with design, obtain insurer pre-design sign-off, and provide a fixed-price proposal backed by an insurance-backed workmanship warranty. Because the design is repeatable, operators rolling solar across a depot network get a consistent specification site to site, which simplifies procurement and reporting across the estate. Installation happens above live operations, with the only outage being the short final grid synchronisation, scheduled out of hours so the morning despatch is never affected. Our MCS, NICEIC, RECC and TrustMark certification and ISO 9001, 14001 and 45001 systems apply on every depot, however small.

An illustrative example

As an illustrative composite based on typical UK depot projects: a last-mile parcel and chilled-grocery depot electrifying its van fleet installed around 300 kW of roughly 555 panels alongside a bank of charge points, generating in the region of 280,000 kWh a year. With vans charging through the day and a chilled loading area drawing power, self-consumption was high, the qualifying cost was written off in year one under the Annual Investment Allowance, and the depot's Scope 2 footprint fell in line with the operator's national programme. The figures are illustrative and depend on your fleet, charging schedule, chilled load, tariff and roof.

If your network includes larger chilled hubs or central handling sites, see cold chain warehouse solar and distribution centre solar. When you are ready, review the cost guide and funding routes, then request a free feasibility or read the cold storage solar FAQs.