Work has begun on a new power link between Britain and France, designed to reduce the risk of blackouts.
A 51km (32 miles) cable will carry direct current through the Channel Tunnel so electricity produced on either side can be imported or exported.
ElecLink, funded by Eurotunnel, is costing £500m.
Energy Minister Jesse Norman said it was the biggest energy infrastructure announcement since Hinckley Point.
The cable will have a capacity of 1,000 MW - equivalent to the electricity consumption of 1.6m households - and will link a substation in Sellindge, Kent, with one 80km (50 miles) away in France.
Mr Norman said:
"As markets expand it makes sense for us to sell energy we don't need at a higher price to the French and to buy energy at a lower price when we do need it it.
"That ends up with a bigger market, that is more secure from our point of view and also less expensive for consumers."
Channel Tunnel chief executive Jacques Gounon added:
"It brings huge security and safety about the supply of energy in Great Britain and on top of that on the French side it brings the possibility to get some green energy."
Eurotunnel is exhibiting at Multimodal on stand FSDF2