Tokelau, consisting of the three atolls of Atafu, Nukunonu and Fakaofo, had previously been dependent on diesel-fueled generators for its electricity.
The $7 million solar project was funded by New Zealand, which administers Tokelau, the BBC reported Wednesday.
The construction of solar grids on the three remote atolls lying between New Zealand and Hawaii was completed this week, officials said.
"The Tokelau Renewable Energy Project is a world first," New Zealand Foreign Affairs Minister Murray McCully said in a statement. "Tokelau's three main atolls now have enough solar capacity, on average, to meet electricity needs."
"Until now, Tokelau has been 100 percent dependent upon diesel for electricity generation, with heavy economic and environmental costs," he said.
Most of Tokelau's 1,500 residents live by subsistence farming, although many islanders have left to settle in New Zealand or neighboring Samoa.