SSE gets Scottish consent to convert Sloy hydro plant into pumped storage scheme

The Sloy Power Station is the largest conventional hydro-electric power station in the UK. · Energy Monitor · SSE

By Anwesha Pattanaik Fri, July 24, 2026 at 4:00 AM PDT 2 min read

SSE has received Section 36 Planning Consent from the Scottish government to proceed with upgrades to the Sloy Hydro-electric Power Station, located at Inveruglas on Loch Lomond's western bank.

The approval gives SSE the option to convert the facility into a pumped storage hydro scheme, which could offer up to 16 GWh of long-duration electricity storage. It also allows for a potential increase in the station's installed generation capacity from 152.5 MW to 160 MW if future asset improvements are implemented.

About Sloy Power Station

• First commissioned in 1950
• Largest conventional hydro-electric power station in the UK
• Current annual generating output: approximately 130 GWh
• Supplies renewable energy to the UK's electricity system
• Capable of reaching full output in under five minutes
• Can operate continuously at maximum capacity for up to 100 hours, supporting grid flexibility and peak demand

Planned Upgrades

The upgrades involve the installation of new pumps near the current site, north of the main power station at Inveruglas. These pumps would allow water from Loch Lomond to be moved to Loch Sloy using up to three of the site's four existing high-pressure pipelines.

This adaptation would enable the facility to generate electricity for longer periods and may help avoid situations where renewable energy from other sources is curtailed during periods of low electricity demand.

Timeline and Investment

SSE indicated it hopes to reach a final investment decision on the Sloy upgrades in late 2027, with the new pumped storage scheme potentially commissioned by the end of this decade.

Statement from SSE

Robert Bryce, SSE Renewables Hydro director, said:

"We're delighted our upgrade proposals for Sloy have received planning consent from the Scottish government.

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"This provides SSE with important optionality for our iconic Sloy Power Station plant, whether as a new pumped storage hydro facility or as a conventional hydro-electric plant with increased generation capacity, and will help ensure Sloy continues to play a vital role in Scotland's energy future.

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"We would also like to take this opportunity to thank key stakeholders, local residents and community groups who have engaged with us so positively throughout the development of these proposals."

Additional Context

Sloy Power Station is connected to the National Grid by a substation with four transformers, which now face replacement due to age.

"SSE wins planning consent for Scotland's Sloy pumped storage conversion option" was originally created and published by Energy Monitor, a GlobalData owned brand.