Hydropower remains a relatively modest but technically significant part of the UK’s energy system, particularly in its role providing stability and flexibility alongside the rapid scale-up of wind and solar. The period to 2035 is expected to see limited growth in conventional hydro, but an emerging resurgence in pumped hydro storage could reshape the sector’s strategic role, the UK Power Market Outlook to 2035 (Update 2025) report from IWP&DC’s parent company Global Data suggests.

Current capacity and generation trends

As of 2024, the capacity of large hydropower in the UK is essentially static at 1.5 GW, while pumped storage sits at 2.7 GW. Together, they contributed around 3.6 TWh of electricity generation in 2024, down from 4.7 TWh in 2020. Forecasts indicate further decline, with combined hydro and pumped-storage output expected to contract at a negative CAGR of 3.4% to just 2.5 TWh by 2035

Hydropower’s share of installed capacity is also expected to diminish — from 3.9% in 2024 to just 2.1% by 2035.  Within that, pumped storage accounts for 2.6% of installed capacity today, while large conventional hydro contributes 1.4% and small hydro only 0.4%.

Operational backbone: existing assets

Key pumped hydro facilities such as Dinorwig (1,728MW, Wales) and Cruachan (440MW, Scotland) continue to underpin grid balancing. Other notable schemes include Foyers (300MW), Ffestiniog (180MW), and conventional plants like Sloy (152.5MW) and Glendoe (100MW).

These stations are among the few dispatchable renewable assets in the UK, providing rapid-response flexibility for frequency regulation, reserve capacity, and integration of variable renewables.

The UK government recognises pumped storage as “essential flexibility infrastructure.” In October 2024, a cap-and-floor revenue mechanism was introduced for long-duration energy storage, including pumped hydro, to provide investment certainty. Policy emphasis is on modernisation of ageing assets and enabling new large-scale pumped storage to complement the offshore wind build-out.

The pipeline of upcoming projects

Although conventional hydro additions will be minimal, there is a substantial pipeline of pumped storage hydro projects:

  • Balmacaan Estate (2,000MW, Scotland) – announced for 2035.
  • Loch Fearna (1,800MW, Scotland) – announced for 2030.
  • Coire Glas (1,500MW, Scotland) – in permitting, targeted for 2031.
  • Balliemeanoch (1,500MW, Scotland) – announced for 2031.
  • Cruachan II (600MW, Scotland) – in permitting, targeted for 2030.
  • Loch Kemp (600MW, Scotland) – in permitting, targeted for 2029.
  • Red John (450MW, Scotland) – in permitting, 2030.

Collectively, these schemes represent more than 8GW of prospective new capacity, signalling a major potential expansion if regulatory and financial hurdles are overcome.

Strategic role to 2035

While hydropower in the UK will not deliver large amounts of bulk generation, its system value is rising. With renewables projected to supply over 75% of capacity by 2035, hydro’s fast-response storage will be critical to managing intermittency. Engineers will increasingly focus on upgrading legacy infrastructure, optimizing efficiency, and delivering new high-capacity pumped storage that can provide both intraday and multiday balancing.