A battery said to be the largest electricity storage facility of its type in Europe, has been switched on in Bedfordshire ahead of a two-year trial.
The 6MW/10MWh battery at the Woodman Close substation in Leighton Buzzard is the size of three tennis courts.
It can store enough energy to power about 6,000 homes for 1.5 hours, at peak times.
The trial by UK Power Networks (UKPN) will look at how it can store energy and cope with peaks in demand.
The Smarter Network Storage facility, housed in a 760 sq m building, is also large enough to power about 1,100 UK homes for a whole day during average or low demand times.
A UKPN spokesman said the trial would "explore and improve the economics of electrical energy storage" and show how batteries can be used "to make electricity networks more efficient".
Director of asset management Barry Hatton, said: "The financial benefits that could be realised from this could be about £600m if this was replicated across the UK by 2040.
"While developing energy storage will not stop the risk of occasional power cuts in local areas, because they can be caused by a variety of reasons, it will help us manage power flows efficiently at times of peak usage."
UK Power Networks distributes more than a quarter of the UK's electricity electricity in the East of England, London and the South East.
The project was funded by £13.2m from the Low Carbon Networks Fund, £4m from UKPN and £1.2m from other businesses and academic institutions.