Sloy/Awe hydro power scheme
The 152.5MW Sloy Power Station and Dam is the largest conventional hydro power station in SSE’s existing hydro power fleet.
Construction on the scheme began in 1945 and was completed in 1951, becoming the first hydro scheme to be developed under the North of Scotland Hydro-Electric Board.
The scheme celebrated its 75th anniversary in 2025.
The existing power station is fed from Loch Sloy, just four kilometres away but, crucially, over 277 metres higher than the power station.
In April 2025 we submitted a planning application to Scottish Ministers for the option to convert the existing facility at Sloy into a pumped storage hydro scheme capable of providing up to 16GWh of long-duration electricity storage, as well as the option to increase the station’s installed generation capacity to 160MW through future asset improvement works.
We are pleased to confirm that in July 2026, we secured Section 36 Consent from the Scottish Government for these future upgrade options at Sloy.
You can find out more about our proposals below and view our Developer Decision Notice here.
Sloy Power Station
We're proposing to convert our iconic 1950s hydro station to pumped storage hydro-electric station.
Following robust consultation process, we are pleased to confirm that consent was granted in July 2026, providing SSE with the option to convert the existing facility into a pumped storage hydro scheme capable of delivering up to 16GWh of long-duration electricity storage. The consent also allows for the option to increase the station's installed generation capacity to 160MW through future asset improvement works.
Our proposals would bolster energy security and help provide the large-scale and flexible renewable energy back-up needed in a future UK net zero power system, helping meet the UK Government’s ambition of Clean Power by 2030.
If approved for delivery, the converted Sloy scheme would be capable of delivering up to 16GWh of long-duration electricity storage capacity.
It could provide firm, flexible renewable energy for up to 100 hours non-stop.
Sloy Power Station redevelopment plansSloy is Britain's largest
Sloy Power Station is Britain’s largest conventional hydro power plant and has been in operation since 1950. It currently generates around 130 million units of electricity in a year of average rainfall.
The current scheme makes use of the water of Loch Sloy, which is carried over 3km by a tunnel through Ben Vorlich before travelling down four high pressure steel pipelines to Sloy Power Station (shown below) at Inveruglas Bay on Loch Lomond.
Inside the power station, four Francis turbines drive four vertical shaft generating sets with a combined generating capacity of 152.5MW.
Pumped Storage Hydro
Pumped storage hydro uses excess electricity during off-peak hours. During this time, it pumps water from a lower reservoir to an upper reservoir. Water is released during peak demand periods. Water flows from the upper reservoir, downhill. As it moves, it passes through turbines to generate electricity.
One of the key advantages of pumped storage hydro is its large-scale storage capacity. This technology has the potential to store massive amounts of energy. This makes it easier to meet high supply demands than other technologies.
Our proposals
Our proposals include the introduction of new pumps located in the grounds of the existing site, immediately north of the power station at Inveruglas on the banks of Loch Lomond.
The new pumps would enable water to be pumped from Loch Lomond to Loch Sloy through up to three of the existing four high-pressure pipelines and tunnels, enabling the scheme to generate for longer periods of time, which would reduce the likelihood of renewable energy from other sources being constrained off the grid during times of low demand.
Our proposal also includes an upgrade to the existing 32.5MW G4 turbine to match its sister units, which would increase the station's generating output by 7.5MW to 160MW.
Image : An architectural concept of the completed development
Section 36 Planning Application - Copy of Public Notice
April 2025 - Section 36 Planning Submission
In April 2025, we submitted an application to the Scottish Ministers under Section 36 of the Electricity Act 1989 to convert Sloy into a pumped storage hydro scheme with a proposed pumping capacity of up to 100MW.
View Sloy planning documentsYour feedback
We would 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. We greatly value the time, feedback and insights shared during the planning process, which have helped shape our approach. Maintaining open and constructive relationships with the communities around Sloy remains extremely important to us.
Contact us
If you have any questions about our proposals or would like to provide any feedback to the project team, please email HydroStakeholderEngagement@sse.com