Brownfield, rooftop, greenfield sites: Why UK solar still needs all three

In a recent planning decision granting approval for the development of a solar farm, two Parish Councils objected, stating that there should be no more solar farms on greenfield sites until all residential and commercial roof spaces and brownfield sites have been “fully utilised”. Arguments for prioritising use of other areas than greenfield sites are fairly common, but this statement can be looked at in more detail to explain why ‘full utilisation’ of rooftop and brownfield sites isn’t necessarily the answer for UK solar delivery.

Rooftop and brownfield solar: Myth v reality

Myth #1: There’s enough rooftop space to meet the UK’s solar needs

Reality: Rooftop solar has enormous potential and should continue to expand. However, many roofs face structural, operational, ownership, funding or grid-connection constraints. Rooftops may be suitable for small scale generation for localised consumption but larger scale generation (whether Utility-scale or large volume private wire offtaker) requires large areas than can be afforded by individual rooftops. The UK government’s solar strategy expressly seeks growth in both rooftop and ground-mounted deployment.

Myth #2: Brownfield land provides a ready-made alternative to greenfield projects

Reality: Some brownfield sites are excellent candidates for solar development. Others are constrained by contamination, remediation requirements, fragmented ownership, redevelopment aspirations, limited site area or poor grid connection opportunities. Not all brownfield land is suitable or commercially viable for solar generation.

Myth #3: Planning policy requires developers to use brownfield sites before greenfield land can be considered

Reality: Planning policy encourages the use of previously developed land, brownfield land, contaminated land, and industrial land where possible, but national energy policy also recognises the need for large-scale ground-mounted solar. The planning system doesn’t impose a strict sequential test requiring developers to exhaust all brownfield opportunities before pursuing a greenfield scheme.

Myth #4: If electricity can be generated on rooftops and brownfield, there’s no need for greenfield solar

Reality: The UK’s clean energy ambitions are likely to require every viable source of low-carbon generation. Behind-the-meter arrangements can provide a supply of a proportion of a consumer’s energy demand via private wire but will often require co-location of the generating site with the consumer, potentially limiting the suitability of rooftops and brownfield land as generating sites.

There are compelling reasons to maximise solar deployment on existing structures and previously developed sites. Rooftop installations generating electricity close to where it’s consumed can help reduce demand on the wider network and provide cheaper electricity to consumers. Brownfield sites can provide productive use for non-green belt land that might otherwise remain underutilised with in many cases reduced concerns over landscape impacts and visual amenity. Stakeholders agree that more rooftop and brownfield solar should be developed, but, as things stand, these opportunities can’t replace the need for larger-scale greenfield solar projects.

UK solar and the challenge of scale

We’ve identified that one of the principal constraints is scale. A single utility-scale solar farm may generate tens or hundreds of megawatts of capacity from one location. Achieving equivalent capacity through rooftop and/or brownfield would not be viable. Such a project would require numerous buildings involving numerous landowners, varying and complex lease arrangements, structural difficulties and extensive project coordination. And that’s not to mention landowners’ limited appetite for long-term energy infrastructure commitments, existing occupational or funding arrangement complexities and significantly higher transaction costs than would otherwise be encountered.

Rooftop installations are better suited to supplying electricity to on site consumers, or sites located in proximity to the identified consumer, where the supply can be made by private wire, without connecting into the public electricity network. The licensing and exemption regime under the Electricity Act 1989 has enabled the growth of these behind-the-meter and private wire projects but there are limitations on the scope to generate and supply under the licence exemptions.

Licensing and regulatory challenges

The regulatory framework under the Electricity Act 1989 governs electricity generation, distribution and supply and the licence exemptions available to generators, distributors and suppliers. In a typical behind-the-meter arrangement, electricity generated by a solar installation is supplied directly to an onsite or nearby industrial or commercial consumer without passing through the public electricity network.

Under the exemptions, a generation licence isn’t required for a generating station producing up to 10MW or up to 50MW for a station with a declared net capacity of less than 100MWs. This is a class exemption for small scale generators, which will often apply to behind-the-meter projects.

Supply licence exemptions can apply where: a non-licensed supplier (or its corporate group) supplies only up to 5MW at any time; or a supplier only supplies electricity which it has itself generated (or together with electricity supplied to them by a licensed supplier) and is supplied to either consumers occupying the same premises, or consumers receiving the supply over a private wire owned by the supplier or the consumer.

Inevitably, locating the generating equipment in proximity to the consumer will be advantageous; a more disparate generating station will increase costs, including infrastructure and land requirements. Equally, the infrastructure and leasing arrangements to site generating equipment at multiple sites (e.g. rooftops) to provide capacity for an off-site private wire arrangement will be more costly and technically challenging.

‘Sleeving’ [1] provides an alternative supply route. This is where the electricity is distributed to the end consumer via the electricity network in an arrangement with a licensed supplier. While sleeving arrangements can overcome geographic separation between generator and user, they can introduce additional contractual complexity, network charges, balancing obligations and licensed supplier involvement, and the additional costs can undermine the commercial rationale for the project.

Currently, it seems unlikely that Ofgem would recommend the loosening of the licensing requirements. “Full utilisation” of brownfield sites and rooftops therefore remains challenging.

Grid and infrastructure constraints

Grid access is another major consideration. The availability of suitable grid connections is one of the most significant factors influencing solar project viability. Developers can’t simply identify vacant roof space or available brownfield sites and expect generation to be deployable at scale. Network capacity constraints, connection costs and connection times can all have a decisive impact on project economics.

So, even where suitable rooftop or brownfield opportunities exist, projects may still face substantial challenges arising from connection delays, reinforcement requirements or limited network capacity.

Planning and national energy policy

A common misconception is that planning policy requires developers to prove that all available rooftop and brownfield opportunities have been exhausted before a greenfield solar project can be approved. Although updated National Planning Policy Framework 2026 (NPPF) strengthens a ‘previously developed first’ approach, that’s not strictly how the current planning and energy policy framework operates.

The position under the NPPF and the energy National Policy Statements, including NPS EN-3, is more nuanced. Policy encourages the use of brownfield and previously developed land where possible and generally seeks to avoid unnecessary impacts on the best and most versatile agricultural land.

UK solar policy involves a broad range of relevant considerations, such as availability of grid connections, generation capacity and efficiency, landscape and visual effects, biodiversity impacts and opportunities, food production considerations, site deliverability, and wider energy policy benefits.

The planning framework increasingly seeks to balance several legitimate and, at times, competing public interests. The result isn’t a simple hierarchy of preferred locations, but a balancing exercise in which rooftop, brownfield and greenfield solar projects all have an important role to play.

Balanced deployment: How we can help

As the UK’s solar future is unlikely to be delivered through a single development model, the debate should focus less on whether rooftop and brownfield solar could be delivered before considering greenfield development, and more on how all three can contribute most effectively to achieving the UK’s clean power, energy security and affordability ambitions.

The energy transition presents increasingly complex legal and commercial challenges across the full spectrum of solar development. Our cross-discipline Infrastructure & Energy specialists can help developers, landowners, investors, funders, energy users and public sector organisations deliver balanced solar development through:

• utility-scale solar farm development
• rooftop and commercial real estate energy projects
• private wire and behind-the-meter arrangements
• electricity licensing and licence-exempt supply structures
• power purchase agreements and sleeving arrangements
• land assembly, options, leases and easements
• planning strategy and consenting
• environmental and biodiversity issues
• grid connection and related infrastructure matters
• acquisitions, disposals and investment transactions
• project financing and energy infrastructure funding.

Whether a project involves a nationally significant energy generation project, commercial rooftop/ground mounted installations or a complex private wire arrangement, early legal input can help identify and overcome legal and regulatory obstacles, facilitate funding arrangements, reduce project risk, and accelerate successful delivery.

Please contact Paul or Ben for further information or advice.

[1] An electricity sleeving arrangement, commonly part of a sleeved Power Purchase Agreement (PPA), is a contract structure where a licensed energy supplier acts as a middleman to perform regulated functions relating to the delivery of power from a renewable generator to a corporate or public buyer via the public grid