Though much of the Pentland Moor wind scheme will feed into the local grid it needs the subsea cable to export a surplus 4.2MW output.
The delay to the interconnector risks a loss of £30,000 a year to crofters and community interests because the turbines will not be able to generate their maximum output.
This is the first time a project of its size has been installed in such a remote and weak electricity network.
Pentland and German manufacturer Enercon are both confident that the 18MW scheme, when completed, will not only operate successfully but will actually help to stabilise the island network as a whole, allowing other community owned wind turbines to follow.
The scheme, sited by protected moorland and golden eagles, was in limbo for much of the past decade due to objections from air traffic control and aviation bodies.
At one point a public inquiry was mooted but negotiations between the developer and National Air Traffic Services, Highlands and Islands Airports which operates Stornoway Airport and the Civil Aviation Authority eventually sorted out the dispute.
SSE Power Distribution is installing an underground cable to connect the new wind
farm control building to the main Stornoway sub-station at the Arnish Road end.
Interconnector delay will affect Pentland Moor windfarm 11/12/12