Solar for chilled last-mile delivery depots

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. Where fleets are electrified, daytime van charging can pair well with rooftop generation: the vans charge while the sun is up, so the illustrative model assumes a high share of generation is used on site; test that against twelve months of half-hourly meter data and the fleet charging profile. Add any on-site chilled storage or refrigerated loading, and the daytime baseload climbs further. Self-consumption is a major driver of solar payback, and the charge-while-you-generate pattern of a last-mile depot tends to support it, giving an illustrative payback of around 5.5 years in the site's simple model (assumed tariff and self-consumption; not a quote), which is sensitive to that assumption.

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 every kWh generated and used on site avoids the energy and network components of the electricity price; network charges (TNUoS and BSUoS) are part of that price and change each year. 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 good match for the solar peak, and the illustrative model assumes it absorbs a high share of the output on site rather than exporting at the lower rate; test that against the fleet charging profile and half-hourly meter data. As more of the fleet electrifies, daytime charging demand may grow, and a depot with solar already installed could see more of the array's output used on site over time. For chilled depots the refrigerated loading and van pre-cooling sit underneath that charging demand as a steady floor, so the self-consumption case may be robust even before the fleet is fully electric. This is why the fleet electrification plan, not just the current load, should be a core input to the depot design.

What a typical install looks like and how it is sized

For a last-mile depot a system is typically 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 would be expected to generate in the region of 92,000 to 370,000 kWh a year and save 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.

The half-hourly meter data and the fleet charging profile should be pulled together, and the system and the charging infrastructure designed 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, the realistic usable roof area should also be checked once rooflights, plant and any shading from neighbouring buildings are allowed for, so the proposed 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 that should be modelled 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

In the site's illustrative model a last-mile depot project lands between £90,000 and £340,000 depending on system size, at an illustrative £700 to £900 per kW (a modelling assumption, not a quote or a market survey). Indicative simple payback sits near 5.5 years in the same model (assumed tariff and self-consumption; not a quote), 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 written off against profit in year one, comfortably within the £1m cap at depot scale, which illustratively is worth up to a quarter of the project value back as tax for a limited company.

Because much of the generation is expected to go straight into the van fleet and any chilled load, the return is driven by avoided import rather than export. The Smart Export Guarantee applies to generators up to 5 MW and the supplier sets the export rate, so compare each supplier's published SEG tariff; it is a minor line here, mainly relevant 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 written off 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, it is worth checking whether Enhanced Capital Allowances apply to 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 a BBP-aligned lease addendum is the form most landlords accept; for owner-occupied or family-owned depots the consent step is usually simpler, though timelines vary by site. 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. The routes that apply to a specific depot, and to a wider network where relevant, are worth mapping before a funding decision is made.

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 the timeline and design should allow for that 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. Before design, ask the site's insurer and a fire-protection engineer about roof loading, clearances and sprinkler compatibility. A grid application is also needed, since G98 'connect and notify' covers only up to 16 A per phase (3.68 kW single-phase, about 11 kW three-phase) and anything larger needs a G99 application and the network operator's approval before connecting. Where chilled storage or refrigerated loading is present on the depot, the F-gas Regulations on that plant continue to apply and the design should allow for them. Wind loading is designed to BS EN 1991-1-4. In England, roof-mounted solar on a non-domestic building is normally permitted development under Class J of Part 14 of the GPDO 2015; an array above 50 kW needs the council's prior-approval decision on design and external appearance, including glare, so for an urban depot the local position is worth confirming early with the council.

How to approach this kind of project

The depot system and the charging infrastructure are best designed together, because on a last-mile site they are inseparable. The starting point is 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. A roof and structural check with a wind-load assessment to BS EN 1991-1-4 should follow, along with confirmation of the usable roof area in an urban setting and an early check of the urban planning position given the more constrained siting.

The G99 grid application is best submitted early so the DNO clock runs in parallel with design, with the insurer's pre-design sign-off sought alongside it. Because the design is repeatable, operators rolling solar across a depot network can aim for a consistent specification site to site, which simplifies procurement and reporting across the estate. Installation can happen above live operations, with the only outage being the short final grid synchronisation, which can be scheduled out of hours so the morning despatch is not affected. When comparing installers, ask what accreditations and insurance the installer holds and ask to see the evidence (MCS covers systems up to 50 kW, which is below the scale of most cold-store arrays), however small the depot.

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 might have an array of around 300 kW and roughly 555 panels alongside a bank of charge points, which would be expected to generate in the region of 280,000 kWh a year. With vans charging through the day and a chilled loading area drawing power, self-consumption would be expected to be high, the qualifying cost could be written off in year one under the Annual Investment Allowance, and the depot's Scope 2 footprint would be expected to fall 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 send an enquiry or read the cold storage solar FAQs.