Permission for the 12-turbine Kirkby Moor Wind Farm was originally granted by the secretary of state in 1992, subject to a condition that the turbines be removed within 25 years of the date they were brought into use.
Zephyr Investments, now Ventient Energy, sought permission in 2015 for a replacement six-turbine windfarm, but permission was refused. The operator subsequently applied to vary the condition attached to the original permission to allow the wind farm to remain operational until 2027.
South Lakeland District Council refused permission in December 2017, on the basis that the benefits of the proposal were outweighed by the adverse effects on the landscape, the setting and character of the Lake District national park and World Heritage Site, and the local economy.
Inspector Phillip Ware advised that a central issue considered as part of the appeal was whether the application represented a "repowering" proposal.
Footnote 49 of the NPPF states: "Except for applications for the repowering of existing wind turbines, a proposed wind energy development involving one or more turbines should not be considered acceptable unless it is in an area identified as suitable for wind energy development in the development plan; and, following consultation, it can be demonstrated that the planning impacts identified by the affected local community have been fully addressed and the proposal has their backing."
Ware noted that "no such suitable areas" have been identified in the local plan and "there is very substantial local opposition".
He said, therefore: "The matter between the parties is whether this proposal is an application for repowering existing turbines."
The inspector advised that the NPPF does not provide a definition of repowering. South Lakeland District Council argued that the application represented a proposal for a new windfarm on the site.
However, Ware said: "The appellant argued persuasively that within the wind industry ‘repowering’ is an umbrella term covering replacement, replanting and extension of life, and this position was not evidentially contested."
He added: "In the absence of national guidance as to the meaning of the term, I consider that the proposal comprises repowering."
Allowing the appeal, the inspector said: "Overall, the continuation of the life of this windfarm for a further limited period would provide benefits in terms of the production of renewable energy and would include decommissioning and restoration advantages.
"These matters outweigh the limited harm which the proposal would cause for the remainder of the life of the installation."
Campaign group Friends of the Lake District, which opposed the application, said it was "disappointed" at the inspector’s decision. "The outcome of this case may influence decisions on other proposals to extend the life of windfarms," it said.
Earlier this week, executives at several large power companies wrote to energy minister Kwasi Kwarteng to call for an overhaul of government planning policy to allow the construction of more onshore wind farms in England.