Ørsted has finished construction on Iceni, a 300 MW, 600 MWh battery storage system near Norwich in England that shares a grid connection with its Hornsea 3 offshore wind farm. It’s the Danish developer’s first large-scale battery in the UK, and when it’s running it’ll rank among the bigger battery energy storage systems in Europe.
The build took about 19 months from a March 5, 2025, construction start ceremony, ESS News reported. Commissioning has started, but Ørsted hasn’t given a date for commercial operation or disclosed what the project cost.
How the Iceni battery storage site was built
Iceni uses 170 Tesla Megapacks. Ørsted’s site photos show the larger Megapack 2XL, though the company hasn’t confirmed the model. Knights Brown was the contractor, with Hitachi Energy and Tesla as the other named partners.
The layout is the unusual part. The battery yards sit on either side of Hornsea 3’s onshore converter station, so the project is split into two areas linked by 18 cross-site 33 kV cables, each more than 600 meters long. Ørsted said sharing a connection point with the wind farm made the engineering harder than a standalone hookup to National Grid would have been.
That’s the trade-off with co-location. The developer saves a separate grid connection, which in Britain can mean a long wait in the queue. In exchange, the battery has to fit around a converter station that was already planned, and every cable run gets longer. Final mechanical and electrical work and the cable terminations are still under way, and crews are preparing to energize the battery’s transformer.
“It’s a milestone moment for Ørsted that construction is now complete on our first large-scale battery energy storage system in the UK,” project manager Beatrice d’Eufemia said, as quoted by New Civil Engineer.
Grid battery safety data looks better every year
Big battery sites still draw local opposition, and the record is improving faster than the reputation. Data compiled by the Electric Power Research Institute and charted by Canary Media on Oct. 23 shows the annual failure rate for commercial and grid-scale batteries fell more than 97% between 2016 and 2025, while cumulative U.S. deployments grew about 250-fold. EPRI now puts grid battery failure rates roughly in line with oil-filled transformers.
The exceptions are memorable. The January 2025 fire at Moss Landing in California injured no one but largely destroyed the plant and forced a multiday evacuation. A 2019 fire near Phoenix seriously injured four firefighters.
What co-located battery storage means for builders
Ørsted has done this in the U.S. too. Its 250 MW, 500 MWh Old 300 Storage project in Needville, Texas, sits beside a 430 MW solar plant and reached commercial operation earlier this year. Storage keeps showing up in smaller packages as well, like the 3.75 MWh installed indoors at a Buffalo affordable housing building.
For electrical contractors, Iceni’s useful number is 18: eighteen medium-voltage cable runs of more than 600 meters each, just to connect one battery to itself around somebody else’s substation.