Common-Parts Solar for Multi-Let Landlords

In a multi-let building the landlord already buys and consumes electricity — the lifts, the communal lighting, the car-park lamps, the HVAC serving common areas. Solar that feeds those landlord-controlled loads is the cleanest route into solar a landlord has, because there is no split incentive to engineer around: the party that pays for the array is the same party that consumes the power and keeps the saving. Every other multi-let route — a landlord-to-tenant PPA, a roof lease, a green-lease contribution — exists to bridge the gap between who pays and who benefits. Common-parts solar removes the gap entirely. It is usually where a multi-let solar programme should start, and on many buildings it carries the whole business case on its own.

Why common parts is the natural starting point

In a single-let or owner-occupied building the economics are simple: one party pays for the solar and one party consumes it. Multi-let breaks that. The landlord owns the roof but the tenants buy the power under their own supply contracts and meters, so a landlord who pays for an array on the roof of a let building cannot capture the saving on the tenant’s bill without a contractual structure — the split incentive that defines this whole asset class.

The landlord-controlled common-parts supply is the one part of a multi-let building that sits entirely on the landlord’s side of that line. The landlord holds the supply contract, pays the bills, and recovers the cost through the service charge — but the consumption is real, continuous and under the landlord’s control. Put solar behind that meter and you displace grid electricity the landlord is already buying, at the landlord’s own import price, with no tenant in the chain.

That has three consequences worth being explicit about:

• No tenant consent on consumption is needed. You are not selling power to anyone or changing how tenants are supplied. You are reducing what the landlord-controlled supply draws from the grid. (Lease and consent points still apply to the physical works and to recovering capital cost — covered below — but the energy flow itself does not depend on tenant agreement.)
• No PPA or sleeving contract is required for this portion. The value lands directly on the landlord-controlled supply bill.
• The saving is the landlord’s to keep or to share. Where the common-parts cost is recovered through the service charge, the saving flows back to the occupiers who fund it — a genuine, evidenced ESG and tenant-relations win rather than a marketing claim.

The typical landlord loads

The landlord-controlled supply in a multi-let building is more substantial than owners often assume, because it runs around the clock and across the whole envelope. Common loads include:

• Lifts and escalators — continuous standby plus duty cycles; a meaningful base load in offices and retail.
• Communal and external lighting — stairwells, corridors, lobbies, signage, car-park and perimeter lighting; increasingly LED but still a steady draw, and external lighting runs at night when solar does not, so it shapes the self-consumption profile.
• Common-area HVAC, ventilation and pumps — air handling for shared spaces, cold-water booster pumps, drainage and sump pumps, smoke-control and pressurisation fans.
• Security and life-safety systems — CCTV, access control, fire alarm and emergency-lighting standby, BMS.
• Car parks — lighting, barriers, ventilation in covered decks; often a daytime load that matches solar generation well.
• EV charging — where the landlord owns and operates charge points on common parts, this is a fast-growing daytime load that pairs strongly with rooftop solar and doubles as a tenant-attraction amenity. Car-park canopies (permitted under Class OA) can host both the charging and additional generation.

The key point for sizing and return is that several of these loads are daytime and weekday-aligned — lifts, common-area HVAC, car-park use, EV charging — which is exactly when a rooftop array generates. That alignment lifts self-consumption, the single biggest driver of return on any commercial array.

What it does to the numbers: service charge and voids

Common-parts solar attacks two distinct costs at once: the recoverable service-charge bill while the building is let, and the landlord’s own holding costs while it is not.

Cutting the recoverable service charge

The cost of the landlord-controlled electricity supply is, in most multi-let leases, recovered from tenants through the service charge. Reducing that grid draw with solar reduces the recoverable bill, which lowers occupational cost for sitting tenants and makes the building cheaper to occupy at the next letting or review. Under the RICS Service Charges in Commercial Property Professional Statement (2nd edition, in force 31 December 2025), the running cost of the supply is recoverable through the service charge — but the initial capital cost of new plant such as solar is not. So the standard treatment is: the capital is funded another way (landlord balance sheet, a capped green-lease contribution, or financed via a roof lease/PPA), and the saving flows through the service charge to the benefit of the occupiers who pay it. Get the recovery mechanism right at the outset; trying to push the capital cost of the array into the service charge is the classic error.

Reducing void holding costs

During a void the landlord carries the building. Lighting, security, ventilation, frost protection, lifts on standby — the common-parts supply keeps running with no tenant to recover the cost from, so it falls straight to the landlord’s bottom line. Solar trims that running cost in exactly the period when the landlord is most exposed. And because the array improves the building’s EPC — solar typically lifts a commercial EPC by one to three bands (never assume a specific jump without a fresh assessment) — it directly supports re-letting. With letting below EPC E unlawful in England and Wales since 1 April 2023, and EPC B by 2031 proposed for privately-rented non-domestic buildings over 1,000 m² (Government interim response, 18 June 2026, subject to secondary legislation), an improved rating shortens voids and protects lettability. See MEES and commercial EPC ratings for the current regulatory position.

Metering: separating landlord and tenant loads

You can only credit solar against the landlord-controlled load if you can measure that load distinctly from tenant consumption. In a multi-let building that means a clean metering architecture.

• Landlord supply on its own meter. The common-parts supply should already sit behind a dedicated meter point; the array connects behind that meter so generation offsets that supply and nothing else.
• MID-approved sub-metering (compliant with the Measuring Instruments Directive) where you need legally robust, billable measurement — essential if any of the energy is to be apportioned or recharged. MID-approved meters give you the evidential standard for service-charge reconciliation and for any future PPA layer.
• Half-hourly data on the landlord supply. Half-hourly import data lets you model the common-parts load profile against the generation profile and size the array honestly — see below. It also lets you reconcile actual self-consumption after commissioning, so the saving you report to tenants is measured, not estimated.

Where the building has a single landlord intake feeding multiple tenant sub-meters, a structural metering review is part of the design work, not an afterthought. Getting the boundaries and the MID compliance right at design stage is what lets the saving be audited cleanly later.

Sizing to the common-parts load

The discipline of common-parts solar is to size the array to the landlord-controlled load, not to the roof. A roof might physically take 400 kWp, but if the common-parts supply only draws enough to self-consume 80 kWp during daylight hours, an oversized array exports the surplus at SEG rates (a supplier-set top-up, currently around 12–15p on the best agnostic fixed tariffs) instead of displacing grid import at the landlord’s own price (roughly 24–28p ex VAT/CCL depending on the supply tier). Self-consumed solar is worth far more than exported solar, so the return is maximised by matching generation to load.

Working method:

1. Pull twelve months of half-hourly data for the landlord supply to establish the true daytime base load and its weekday/weekend, summer/winter shape.
2. Size the array so most generation is self-consumed by the common-parts load across the year — typically meaning the array is comfortably smaller than the roof could hold.
3. Then decide what to do with the spare roof. This is the bridge to the rest of the building.

Self-consumption on a common-parts-only array tends to sit in the 30–50% range for a daytime-skewed landlord load without storage, rising with battery or with high daytime loads like EV charging and car-park ventilation. A small co-located battery can shift evening security and lighting load onto stored solar and lift self-consumption further; rooftop solar with co-located storage is 100% exempt from business rates in England to 31 March 2035.

Combining with a tenant PPA for the rest

Once the array is sized to the common-parts load, the remaining roof is where the wider multi-let opportunity lives. The natural next layer is a landlord-to-tenant PPA: the spare generation capacity is sold to the occupying tenants behind the meter at a price set below their grid import, turning what would have been low-value export into displaced retail-price electricity for the tenant and a margin or amenity for the landlord. That route does require tenant agreement and a supply contract, and it carries its own consent and metering work — which is precisely why it sits as a second phase. The full mechanics, pricing logic and private-wire and sleeving options are set out in landlord-to-tenant PPA and private wire.

A clean sequencing for a multi-let asset, then, looks like this:

1. Phase one — common parts. Size to the landlord load, no split incentive, value captured immediately on the landlord supply, service charge and void costs cut, EPC improved.
2. Phase two — the spare roof. Add capacity and contract it to tenants via PPA (or lease the airspace to a third-party developer if you would rather not fund or operate it), bridging the split incentive for the occupied units.

Phase one stands entirely on its own. It needs no tenant on board, lands a measurable saving, and improves the asset’s regulatory position and lettability. For most landlords it is the right first move on a multi-let commercial building, with the tenant-facing layer added once the building’s own supply is already working harder. To model the common-parts load and the array that suits it, request a quote with twelve months of half-hourly data for the landlord supply.

Frequently asked questions

Does common-parts solar really need no tenant consent?

For the energy itself, no — you are reducing what the landlord-controlled supply draws from the grid, not changing how any tenant is supplied or billed, so consumption needs no tenant agreement. What still needs attention is the physical works and the recovery of cost: the lease may govern roof access and alterations, and the RICS Service Charges Professional Statement (2nd edition, in force 31 December 2025) means the array’s capital cost cannot simply be pushed into the service charge. Tenant consent re-enters the picture only when you move to phase two and start selling spare generation to occupiers under a PPA.

How much can a landlord save on a typical multi-let?

It depends entirely on the size and shape of the landlord-controlled load, which is why twelve months of half-hourly data comes first. As a frame, self-consumed solar displaces grid electricity at roughly 24–28p per kWh (ex VAT/CCL) against an export value of around 12–15p under the best fixed SEG tariffs, so the return is driven by how much generation the common-parts load can absorb during daylight. A daytime-skewed load — lifts, common-area HVAC, car-park and EV charging — typically self-consumes 30–50% of an unstored array, rising with battery storage. The honest answer is that the array should be sized to that load and the saving modelled from measured data, not promised as a headline figure.

Who keeps the saving — the landlord or the tenants?

It follows the money. Where the common-parts supply is recovered through the service charge, the saving flows back to the occupiers who fund that charge, lowering their occupational cost — a real, evidenced benefit you can take to tenants. Where the building is void, or where the landlord absorbs an unrecovered portion, the landlord keeps that share directly. Either way the array improves the asset: a lower service charge supports rent and lettings, and reduced void holding costs protect the landlord’s position between tenancies.

What metering do we need to make this work?

A dedicated meter on the landlord-controlled supply so the array offsets that load and nothing else, MID-approved sub-metering wherever energy is apportioned or recharged so the measurement is legally robust, and half-hourly data so you can both size the array honestly and reconcile the actual saving after commissioning. In buildings with a single landlord intake feeding tenant sub-meters, the metering boundaries should be reviewed at design stage — getting the architecture and MID compliance right up front is what lets the saving be audited cleanly for the service charge and lets a tenant PPA be layered on later without re-engineering the meters.