Residents of the island, which sits halfway between Orkney and Shetland and has a population of 55, used to have their power supply turned off between 11.30pm and 7.30am.
Electricity was powered by wind and two generators, with the costly diesel-run kit switched off overnight to save resources.
While some residents built back-up battery supplies for their homes and businesses - including the island’s shop in order to keep its freezers running - many were left powerless throughout the night.
Now, a round-the clock supply has been secured with a £3.5 million renewable electricity system officially launched today.
Fair Isle Electricity Company (FIEC), the community-led organisation that led the energy project, hopes the stable supply will help to draw more people to live and work on the island.
Robert Mitchell, company director of FIEC who also runs the Fair Isle shop and post office with his wife Fiona, said the new system would save islander’s money given battery back up would no longer be required and generators seldom used.
Mr Mitchell said: We have had times in the past when the children were young and they wouldn’t be very well, they’d be having a bad night, and you would be trying to find a torch.
“Also, if we had an emergency here and a nurse was being called out to see a sick person that we had to get out of bed to go and put the generators on so we could go an alert the coastguard and so on.
“Power on the island has always been a major hurdle and now that has been overcome.”
Mr Mitchell said he hoped the new power supply would help boost the population of the island, which has fallen from just over 80 to 55 over the past 25 years.
He said: “The population has been in slow decline. You get families come and they might stay for a couple of years. Quite often they the reason is there is not enough income and they don’t like having the power go off.
“We asked all the islanders for help working out what was needed. We asked children who moved away what, if they moved back, what they would like to see. They said they would want 24-hour access to the internet.”
Other planned community-led projects on Fair Isle include the building of one and two-bedroom properties to offer good housing to single people and couples as well as improvements to the ferry service.
The new energy system combines three wind turbine generators, ground-mounted solar panels and battery storage with the generators to be retained for emergencies.
Diesel to run the equipment cost around £1,500 a month with transportation costs by ferry an added expense, Mr Mitchell said.
“It’s has been an ambitious project and is another step in ensuring that the community of Fair Isle continues to thrive,” he added.
The new system was backed by £1.5 million from the Scottish Government and £250,000 from development agency Highlands and Islands Enterprise.
The 24-hour power system has been working for two weeks with the official launch of the project today.
Scottish Minister for Energy, Connectivity and the Islands, Paul Wheelhouse said: “Those of us living on the mainland of Scotland can often take reliable supplies of electricity for granted.
“This has never been possible for the islanders of Fair Isle.
“The reality of having, for the first time in their history, 24-hour supplies of electricity presents exciting prospects for the Fair Isle community, who will not only benefit from access to a reliable electricity supply around the clock, but also now have in place a new cleaner, greener energy system.”
Alan Rankin, Islands Operational Manager at National Trust for Scotland, which owns the island and most of the properties on it, said: “This is a big milestone for the community of Fair Isle.
“The new renewable energy system is going to make a massive difference to them all and to the future of the island. A huge congratulations to all involved in the project which the Trust was pleased to play a part in supporting.”