Welsh firm Infinite has been selected by Chief Pleas to produce detailed plans for the new scheme, alongside partners Sancus Utilities.
But the boss of Sark Electricity has labelled the spending a "massive middle finger to the taxpayers of Sark".
Managing director, Alan Witney-Price, said he thought the scheme would come to nothing when politicians saw the final price.
Logistically challenging
Experts Communities for Renewables, who have worked with Chief Pleas on the scheme, estimated it could cost around £8.6m.
The head of operations and project delivery at Infinite, Gillian Jones, said: "We are excited to be bringing our expertise in renewable energy and micro girds to Sark.
"Our aim is to design an energy centre that provides greener, more secure, reliable, and cost-effective power to the residents and businesses on the island."
Ms Jones said the company would be working with specialists from the Netherlands who were experts in installing renewable technology on islands.
She added: "We'll bring most of the big kit over on a heavy barge with a crane on to Masseline Harbour... then we'll have to get it through the tunnel, up the Harbour Hill and around some small windy lanes."
Infinite director, Lestyn Morgan said the project could showcase technology which could be replicated on islands around the world.
The company has said it would now work out "the best mix and capacity of wind, solar, battery storage as well as back-up diesel generators" before coming back with plans before the end of June.
Cost concerns
Conseillers at Chief Pleas' Christmas meeting said they were happy they were being given the option to go for a mix of power solutions, as they were concerned about the potential cost of a fully renewable grid.
Chair of Sark's most senior committee Policy and Finance John Guille said he was confident funding for the project could be found.
