Common-Area vs Whole-Roof Solar for Shopping Centres

Most guides to solar panels for shopping centres stop at the headline numbers. The harder question, the one that decides how a scheme is actually built, is how much of the roof to fill. A shopping centre is not one electricity bill. The landlord pays for common-area or landlord-supply power, the mall lighting, lifts and escalators, ventilation and comfort cooling in common parts, car-park lighting and management suite, recovered from tenants through the service charge. Each retail unit is separately metered and buys its own power directly. That split is the whole game. You can size an array purely to cover the landlord-controlled common-area demand, or maximise the roof and take on the job of selling or allocating the surplus to tenants. This guide compares the two routes on the terms that matter to a landlord or asset manager. The right answer depends on your scheme, common-area load profile and tariff. The main guide to solar panels for shopping centres sets out how the common-area load is measured.

The two routes in plain terms

Common-area-sized solar. You size the array to the landlord-controlled load and nothing more. The owner self-consumes the generation directly against common-area demand, the saving flows straight through the service charge, and because nothing crosses a tenant meter there are no supply agreements, no embedded-network licensing and no green-lease negotiation to complete before the panels earn. It is the simpler, cleaner, faster-to-build route, and on a well-sized scheme almost every unit generated is self-consumed at full value.

Whole-roof solar. You fill the available roof (and often the car park) to its sensible structural and grid limit, well beyond what the common-area load alone can absorb. The generation that exceeds common-area demand has to go somewhere useful: sold to the tenants through a private-wire or embedded-network arrangement, allocated via a green lease, or exported to the grid at the lower Smart Export Guarantee rate. The prize is far more generation and a stronger asset-level net-zero and EPC story across the whole centre. The cost is real commercial and regulatory complexity, because you are now, in effect, supplying power to third parties, so check the arrangement with the supplier and a lawyer.

Where the options differ

The main differences fall out across the two approaches:

Factor	Common-area-sized	Whole-roof
Who benefits	Landlord directly, tenants via lower service charge	Landlord plus tenants who buy or are allocated the power
Billing / service-charge mechanics	Self-consumed against common parts, recovered through service charge	Private wire, embedded network or green-lease allocation to tenant meters
Capex	Lower, matched to common-area kW	Higher, fills the roof and often the car park
Self-consumption value	Very high, most units used at full retail offset	High on the common-area share, surplus shared with tenants or exported at SEG
Complexity	Low, no tenant agreements needed	High, supply, metering and licensing to structure
EPC / lettability reach	Improves the common parts and the asset story	Improves common parts and the units the power reaches
Best fit	Owner wanting a clean, fast, low-risk scheme	Large roof, engaged tenants, long hold, portfolio net-zero target

The headline trade is reach versus simplicity. Sizing to the common-area load gives you the fastest, lowest-risk scheme with the cleanest service-charge story, but it leaves a large part of the roof empty and the generation potential of the asset only partly used. Going whole-roof captures far more of that potential and spreads the benefit across the centre, but only if you build and run the commercial machinery to get the surplus to tenants, and that machinery is where most shopping-centre schemes either stall or quietly scale back.

The service-charge, landlord-supply and tenant-allocation angle

This is the part competitors leave unaddressed, and it is the part that actually decides the route.

Common-area-sized solar lives entirely inside a structure landlords already run every day: the service charge. Common-area electricity is a service-charge cost, on-site generation lowers that cost, and the reduction is passed back to tenants the same way every other common-area saving is. There is nothing new to license and no power crossing a meter you do not own, which is why it is the default for most multi-let assets and the route that proceeds fastest.

Whole-roof solar pushes you past that boundary. To use generation above common-area demand you have to get it onto tenant meters, and that means one of three structures. A green-lease framework can allocate or share surplus with tenants and set out who funds the install and who benefits; it is the lightest-touch option. A private-wire or embedded-network arrangement physically supplies tenants with on-site power and can be the most valuable route, but it carries metering, billing and electricity-supply obligations that have to be set up and run, and whether you may resell power to tenants needs checking with the supplier and a lawyer first. Pure export sends the surplus to the grid through the Smart Export Guarantee, the simplest fallback but the lowest paid, at a supplier-set rate against the full retail value of a self-consumed unit.

There is also the roof-rights question. On many centres the roof above a unit is demised to the tenant, so before a landlord can fill it the leases need a roof-rights clause or a lease addendum reserving the landlord’s right to the roof for generation. Common-area-sized schemes can often sit on plant, mall and car-park roofs the landlord already controls; whole-roof schemes almost always touch demised roof space and therefore the leases. None of this is a reason to avoid whole-roof solar. It is the reason it has to be planned commercially, not just engineered, and the reason the structuring should be settled before anything goes on the roof.

How the two routes compare

A common-area-sized scheme is matched to the predictable common-area load, so self-consumption is high. Crucially it needs no tenant supply agreements, so it can proceed on the landlord's decision alone.

A whole-roof scheme fills the roofs and may add a car-park canopy, well beyond what the common-area load can absorb. It would generate considerably more, but the extra generation only earns its keep if it reaches the tenant units through a green-lease allocation or an embedded network, which needs checking with the supplier and a lawyer. Build that structure and the asset-level saving and net-zero reach are materially larger; fail to agree it and much of the surplus falls back to the export rate, weakening the case on the incremental kW. How this plays out depends entirely on your scheme, roof, load, tariff and lease structure.

How to choose

The decision tree is short. If you want the cleanest, fastest, lowest-risk scheme and you are content to capture the landlord-controlled saving, size to the common-area load. It proceeds on your own decision, the service-charge mechanics already exist, and almost every unit generated is used at full value.

Go whole-roof when three things line up: a roof (and ideally a car park) large enough to justify the extra capacity, tenants or a lease structure that give you a real route to allocate or sell the surplus, and a hold horizon long enough to earn the larger investment back. A portfolio net-zero target or the proposed MEES move to EPC B from 2031 for let buildings over 1,000 m2, where cost effective, often tips the balance toward filling the roof, because the EPC and lettability benefit then reaches the units, not just the common parts.

In practice an owner can phase it: build the common-area-sized array first for the certain, fast return, while putting the green-lease or embedded-network structure in place to switch on the rest of the roof once tenants are signed up. The way to know which route fits is to size the array from your common-area load against at least twelve months of half-hourly meter data, then test what an agreed tenant route would add on top. See the cost guide and funding routes for the background, model the saving on the savings calculator, and read whether solar is worth it for shopping centres for the wider case. When you are ready, get a quote; whoever models the scheme should show the common-area-sized and whole-roof routes side by side. We reply by email.