Worked example: Multi-site PPA Portfolio for a London Borough
An illustrative 2,100 kWp public sector solar PPA: at 11.5 p/kWh over 25 years, the modelled year-1 saving is £270,000.
Illustrative example — not a real deal
This is a hypothetical worked example, written to show how a solar PPA's numbers work for this kind of site. The site, the operator and every figure are illustrative: the tariff and term sit inside this site's indicative bands and the saving is modelled from them. It does not describe any real organisation, and no contract is claimed.
| Worked example — modelled figures | |
|---|---|
| Sector | Public sector |
| System size | 2,100 kWp |
| PPA tariff (year 1) | 11.5 p/kWh |
| Contract term | 25 years |
| Year-1 saving (modelled) | £270,000 |
A London borough portfolio, as an illustration
What follows is an illustrative public-sector portfolio, not an identifiable council. Imagine a London borough with fourteen operational buildings in scope — four leisure centres, two town halls, eight schools and three depots. It carried a corporate net-zero target for 2030, its Salix recycling fund was already fully committed, and there was firm political resistance to taking on fresh borrowing. That last constraint is decisive: it rules out most capital routes and points straight at funding that keeps the balance sheet clear. Fourteen buildings of very different ages and roof types also meant the technical picture varied enormously from one site to the next.
Why aggregation and a PPA fit the brief
Bundling every site into a single aggregated PPA did two useful things. It kept the whole programme off the balance sheet, sidestepping the borrowing objection, and it gave bidders enough combined scale to sharpen the tariff. Aggregation also spreads the fixed costs of survey, legal work and grid applications across a far larger generating base — a big part of why the blended rate came in as low as it did. A borough covenant is strong from a funder's view too, which widens the field of willing providers, and it is exactly why the off-taker covenant question weighs so heavily in public-sector deals.
The procurement reality
Public bodies can't simply sign; this went through a compliant competitive tender, and the timeline reflected that:
- Around fourteen months from launch to contract via a PCR 2015 / PA 2023-compliant process
- An extra twelve weeks for member-committee sign-off on the above-£500k award
- Two leisure-centre roofs dropped from scope after structural surveys
Indicative outcome
On the seed figures the portfolio saves about £270,000 in its first year at 11.5 p/kWh over 25 years, and the net-zero milestone lands on schedule — with the programme later used as a reference by neighbouring authorities. For a council, that repeatability often matters as much as the cash. If you're scoping something similar, compare delivery routes in the options comparison and shortlist funders through the provider directory.
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