Adjacent solar developments ruled not to be a single NSIP

A recent High Court judgment has clarified that a proposed solar farm located adjacent to an existing solar farm is considered a separate generating station and the applicant does not have to seek consent under the Nationally Significant Infrastructure Project (“NSIP”) planning regime.

In Drayton Manor Farms Limited v Stratford-upon-Avon District Council, the claimant sought a declaration that its proposed solar farm was not an extension of the existing solar farm at Drayton Manor Farm under sections 14 and 15 of the Planning Act 2008 (“2008 Act”) and does not require development consent in accordance with section 31 of the 2008 Act. In his judgment granting the declaration, Mr Justice Mould clarified the key to determining whether the proposed solar farm was an extension was whether there will be interdependence between the two facilities in their function of generating electricity from solar power. In this case, there was not.

Factual Background

The claim concerned development for a 32 mega watt (MW) solar farm and change of use of two dwellings to a solar control building with associated works on land at Drayton Manor Farm, Stratford-Upon-Avon ("the Development").

In 2023, Stratford-Upon-Avon District Council, granted planning permission for the Development ("the 2023 Planning Permission"). This permission included notes referencing that the Development was an extension on an existing, adjacent 50MW solar farm. The note indicated that if the new solar farm is considered an extension of the existing one, the combined generating capacity would exceed the 50 MW threshold set by section 15(2)(c) of the 2008 Act for onshore generating stations in England. Consequently, the new Development would fall within the definition of a NSIP under section 14(1)(a) of the 2008 Act, as it involves the construction or extension of a generating station.

Section 31 of the 2008 Act requires development consent for projects that are part of a NSIP. Additionally, Section 160 of the 2008 Act states that it is an offence to carry out development requiring development consent without a valid development consent being in force.

The claimant wished to proceed with the Development, but the note included in the 2023 Planning Permission created uncertainty about whether this would constitute a criminal offence under Section 160. The claimant sought a court declaration that the Development is not an extension of the existing solar farm under sections 14 and 15 of the 2008 Act, and therefore does not require development consent under Section 31.

The decision

Mr Justice Mould noted that the 2008 Act does not provide a statutory procedure for obtaining a conclusive determination either from the Secretary of State or the court as to whether a given project falls within the definition of NSIP for the purposes of that Act. There is no corresponding procedure to that enacted under section 192 of the Town and Country Planning Act 1990 ("the 1990 Act") and the Planning Inspectorate cannot give a conclusive opinion on this.

Mr Justice Mould considered the question of whether the solar farm authorised by the 2023 Planning Permission should be seen as a separate electricity generating station from the existing one, noting that this determination was, to some degree, “a matter of impression”.

Mr Justice Mould emphasised that the key factor in determining whether the two solar farms are interdependent is their function of generating electricity. He found very little, if any, interdependence between the 2015 and 2023 solar farms in their core operations. The proximity of the two facilities within the same freehold landholding was deemed less significant compared to their generating capacity, which is the basis for the NSIP threshold under the 2008 Act.

Additionally, there are separate leasehold owners and operators for the facilities, and they will operate under different lifecycles, conditions and controls. For these reasons, Justice Mould held that the Development is not an extension of the existing generating station, but a separate generating station in its own right. As its proposed capacity is below the threshold stated in section 15 of the 2008 Act, it does not require development consent under section 31.

TLT's opinion

In considering the requested declaration, the judge highlighted the uncertainty the note on the 2023 Planning Permission created and the lack of statutory process for resolving this. He therefore considered making the declaration was the only effective form of resolving this uncertainty. This follows the earlier decision in Durham County Council & Hartlepool Borough Council v The Secretary of State for Levelling-up, Housing and Communities [2023] EWHC 1394 (Admin).

The judgment clarifies that adjacent, separately authorised and independent solar farms are unlikely to be treated as single generating station and do not require authorisation under the 2008 Act.

The key factor in determining whether such developments fall within the 2008 Act is the extent of and any interdependence between the two facilities in their function of generating electricity. To avoid the NSIP regime, developers should ensure there is severability and operational independence between adjoining facilities. Alternatively, to bring multiple smaller clusters within the NSIP regime to utilise the benefits, there must be interdependence between the facilities in their function of generating electricity, noting that it is always possible to make a request under section 35 to “opt in” to the NSIP regime, and under the proposals included in the Planning and Infrastructure Bill it may be possible to “opt out” even if the threshold is met.

While this case settles the position in relation to adjacent solar developments, the draft statutory instrument containing the proposed amendments to the 2008 Act to bring in onshore wind and raise the threshold for solar (from 50MW to 100MW) creates potential uncertainty as to how to treat developments of adjacent or co-located wind and solar. The proposals for the amended section 15 of the 2008 Act sets out that the construction/extension of “a generation station” is an NSIP where it “generates electricity from wind or directly from sunlight” and has a capacity of 100MW.

Katherine Evans Head of Planning and Environment said that the use of a note on a planning permission by the local planning authority which has no legal status should not have been used in order to avoid the local planning authority having to make a decision on whether the development proposed could have been authorised under the 1990 Act rather than the 2008 Act. Whilst this case may have clarified the position as to how to treat adjoining developments to some extent, with upcoming changes to planning legislation, we suspect that there may be further litigation especially around combined wind and solar developments.

Our Future Energy Planning and Environment team are experts in both NSIP and TCPA developments and can advise developers on how to design a scheme to either opt in or out of the NSIP regime and the pros and cons of the regime compared to consenting a scheme under the 1990 Act.

Please get in touch with our experts to discuss the matters raised in this article.

This publication is intended for general guidance and represents our understanding of the relevant law and practice as at April 2025. Specific advice should be sought for specific cases. For more information see our terms & conditions.