The island of Ta'u in American Samoa, 4,000 miles from the U.S. West Coast, now has a solar power and battery storage microgrid with 1.4 megawatts of solar generation capacity and six megawatt hours of battery storage from 60 Tesla Powerpacks, the blog said.
That was enough to supply nearly all of the power needs for the island's residents, which number around 600, according to the blog.
The grid replaces the more than 109,500 gallons of diesel the remote island imported every year to power generators and would be more reliable, likely eliminating the need for power rationing, the blog said.
Keith Ahsoon, a local resident whose family owns one of the food stores on the island, told SolarCity that residents relied on boat delivery for almost everything.
"I recall a time they weren't able to get the boat out here for two months," he said, according to the blog.
"Once diesel gets low, we try to save it by using it only for mornings and afternoons. Water systems here also use pumps, everyone in the village uses and depends on that," Ahsoon added, recalling using candlelight while growing up.
It took a year to install the new grid, which was funded by the American Samoa Economic Development Authority, the Environmental Protection Agency and the Department of the Interior, the blog said.
Ahsoon noted that using solar and cutting the island's carbon footprint was one of the system's attractions.
"Living on an island, you experience global warming first-hand. Beach erosion and other noticeable changes are a part of life here. It's a serious problem, and this project will hopefully set a good example for everyone else to follow," he said.
The announcement about Ta'u's new grid came as shareholders approved Tesla CEO and founder Musk move to merge Tesla with Solar City, for which Tesla paid $2.6 billion. Musk owned 22 percent each of SolarCity and Tesla.
At the shareholder meeting last week, Musk said SolarCity's newly launched solar roof tiles would be competitive with traditional tiles.
"The apples-to-apples comparison compared to a regular roof will be at least at, and we believe slightly below the cost of a regular roof, and the electricity is just a bonus," Musk said, adding that would include labor costs and exclude any money from subsidies.
Last year, Tesla Energy launched its line of Powerwall rechargeable batteries for home, business and utility use, which was designed to work with solar systems to store energy. At the time, Tesla said the Powerwall home battery, a 7-10 kwh lithium-ion battery would be priced at $3,000-$3,500 for installers.
—Robert Ferris contributed to this article.
—By CNBC.Com's Leslie Shaffer; Follow her on Twitter