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Britain’s largest battery is actually a lake

Tom Scott | March 1, 2026



Dinorwig Power Station, otherwise known as Electric Mountain, is a pumped-storage hydro station in Llanberis, Wales. And yes: it’s Britain’s largest battery. Here’s how it works, and why some of the things you think you know about TV pickups might not be so true any more.

Thanks to all the Engie team! More about them: https://www.engie.com/

Camera op: Ryan Priestnall
Editor: Michelle Martin https://www.youtube.com/@OnTheCrux

I’m at http://tomscott.com
on Twitter at http://twitter.com/tomscott
on Facebook at http://facebook.com/tomscott
and on Instagram as tomscottgo

Written by Tom Scott

Comments

This post currently has 31 comments.

  1. @zenjifugimoto

    March 1, 2026 at 7:25 pm

    I'm gonna setup my offgrid house to automatically turn on a pump whenever the batteries get full, which will pump water up to a higher area, and then I can use hydro electricity to harvest that potential energy and recharge my normal batteries.

  2. @matt9c1

    March 1, 2026 at 7:25 pm

    I got to take a tour of this place back in 2009. It was amazing.
    Thank You for making this video, it was a nice blast from the past 🙂

  19. @OldScientist

    March 1, 2026 at 7:25 pm

    The Royal Society recommend the UK should have 100TWh of energy storage by 2050 (it's currently 39.3 GWh from 4 pumped storage facilities). That's over a 2,500 fold increase. That means building 10,000 pumped storage facilities or 400 every year. A typical pumped storage facility has a 300 to 400m dam built to hold back 10 million cubic metres of water, with a fall to the turbines below of about 400 metres.

    That's at the same time as increasing wind power generation from 75TWh (in 2020) to 665TWh (in 2050 – these are UK National Grid figures). That's around 100,000 giant wind turbines. And by the time you get to 2050, the 4,000 wind turbines you needed to install in 2025 would have reached the end of their working lives and will need to be buried in landfill, and replaced with another 4,000. It's all impossible and absurd.

    The cabling and additional structures to connect all this together will essentially require the UK consuming all of the current global supply of copper and other rare metals for the next 25 years. The cost will be unaffordable and the skilled manpower levels unattainable. And that is just to eliminate the less than 1% of the global CO2 emissions that the UK is responsible for. So times that by 100 for the whole Earth going Net Zero. Good luck with that.

  21. @G6JPG

    March 1, 2026 at 7:25 pm

    Isn't there some rule about vehicles must be left unlocked with the keys in, so that if the mechanism goes wrong, the staff have a slight chance of escaping the water?

  29. @theindiefanclub

    March 1, 2026 at 7:25 pm

    Very disappointing that the great museum and visitor centre in Llanberis has closed for 'renovation' and never re-opened, and now the council is considering cheaping out and turning it into a car park :/

Comments are closed.

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