Committee publication · Scrutiny evidence · 15 October 2025 · HC 459
Visit note - Visit to Loch Sloy Hydro-Electric Scheme
Summary
The Scottish Affairs Committee visited SSE's Loch Sloy hydro-electric scheme on 29 August 2025 as part of its inquiry into GB Energy and the Net Zero Transition. The 152.5 MW facility, operational since 1949, briefed the committee on its current operations and SSE's proposed pumped storage expansion. SSE highlighted regulatory barriers, particularly Ofgem's Cap and Floor mechanism for Long Duration Energy Storage, which it says makes the planned Coire Glas 1.5 GW project unviable and risks disadvantaging pumped hydro against battery storage.
Key findings
- Loch Sloy has a capacity of 152.5 MW, the largest among SSE's conventional hydro stations, and generates electricity by releasing stored water through a turbine-driven generator.
- SSE proposes a pumped storage scheme at Loch Sloy to store excess grid energy overnight or during oversupply periods, addressing increased demand for storage as intermittent renewables expand.
- The proposed Coire Glas pumped storage project (1.5 GW, between Fort William and Inverness) is currently not investable under Ofgem's Cap and Floor mechanism for Long Duration Energy Storage.
- SSE argues the Cap and Floor scheme, copied from interconnector regulations, does not fit pumped hydro's different risk and return profile, and risks battery projects displacing pumped storage hydro developments.
- The visit included briefings by SSE's Director of Hydro Robert Bryce, Head of Hydro Operations Peter Diver, and Head of Stakeholder Engagement Corinna Scholes, plus site tours of the dam, tunnel, and power station.
Tone
ProceduralTopics
Key actors
Scottish Affairs Committee, SSE, Patricia Ferguson MP, Susan Murray MP, Kirsteen Sullivan MP, Robert Bryce, Peter Diver, Corinna Scholes
Notable line
“… investable. It says it has been copied from the scheme for interconnectors, even though pumped storage hydro has a different risk and return profile compared with interconnector projects.”
Key Quotes
“The site has a capacity of 152.5 Megawatts, which is the largest capacity of SSE's conventional hydro power stations.”
“… the proposed development would pump water during times of low demand (typically overnight) or oversupply (when there is too much renewable energy being generated).”
“SSE welcomed the mechanism in principle but said the current scheme design is not investable. It says it has been copied from the scheme for interconnectors, even though pumped storage hydro has a different risk and return profile compared with interconnector projects.”
“… there is a significant danger that battery projects, which do not need the Cap and Floor, will push out pumped storage hydro projects.”
Source · parliament.uk record ↗