Plans for a £600m subsea power cable which would take energy from Shetland to the Scottish mainland have been approved by energy regulator Ofgem.
Scottish and Southern Electricity Networks (SSEN) wants to build a 600MW electricity transmission link.
It would allow new wind farms on Shetland to export renewable electricity to the rest of Britain.
Ofgem said it was conditional on it being satisfied by the end of 2020 a major wind farm was likely to go ahead.
That planned £580m Viking Energy project would involve 103-turbines.
It would be the UK's largest onshore wind farm in terms of annual electricity output.
It is estimated that the subsea cable project would cost more than £600m.
SSE chief executive Alistair Phillips-Davies said the decision marked a "significant milestone".
He said: "It has been a long journey, but with a combined investment in excess of £1bn, the construction of the subsea transmission link, all associated onshore infrastructure and the Viking Energy wind farm will deliver substantial socio-economic and environmental benefits to Shetland's, Scotland's and the UK's economy, supporting hundreds of skilled jobs in the process."
The power cable project would connect Kergord in Shetland to Noss Head on the Scottish mainland, near Wick in Caithness.