Solar power is ?? ??? ??? ?? ?? 1973bringing light to remote villages across India. Rural residents, long disconnected from the grid, are increasingly using solar panels and battery banks to charge mobile phones, illuminate light bulbs, and keep refrigerators humming.

Advocates for rural electrification say solar "microgrids" can do much more. They'll boost a village's socioeconomic development by allowing kids to study at night, for instance, or by enabling residents to open local shops and use time-saving tools like electric water pumps and mills.

However, that scenario is still only a dream in many places, researchers said in a paper published Wednesday in Science Advances.

Solar microgrids in India's northern Uttar Pradesh state did little to improve household incomes, encourage business ownership, or reduce the long hours that people spend on daily household work, the new study found.

Villagers did buy less kerosene for their lamps, since they could flip on light bulbs at night. But their lives were otherwise unchanged, according to a yearlong, randomized survey of nearly 1,300 households in 81 non-electrified rural communities.

"For the most part, we found overwhelmingly little socioeconomic effect," Michaël Aklin, the study's lead author and a political science professor at the University of Pittsburgh, said in an interview.

That doesn't mean solar microgrids aren't worth the investment or won't deliver the promised results one day, he said.

But it does show that local officials, energy companies, and NGOs alike need to address other pressing issues -- such as underfunded schools or dismal job prospects -- before rural electrification can really lift people out of poverty.

"We're moving away from a slightly naive sense of this magical solution to having a more robust discussion," Aklin said. "Putting up a solar panel is not going to be enough. So what else do we need?"

Rural electrification is a key part of the Indian government's plan to boost the economy in the nation of 1.3 billion people. About a quarter of the population, or more than 300 million people, still aren't connected to a reliable power source.

Indian Prime Minister Narendra Modi has pledged to meet these electrification goals by installing record amounts of renewable energy. In 2014, he set a target to increase India's solar power capacity to 100 gigawatts by 2022, about an eight-fold increase from today's 12.3 gigawatts.

India's Remote Village Electrification Program has helped install thousands of subsidized solar panel systems and solar microgrids throughout rural India. But these, too, have had an underwhelming performance in many places, according to a 2016 study from India's central Chhattisgarh state.

Without battery backups, solar panels provide little use to communities at night. If villagers aren't adequately trained to maintain them, systems can fall into disrepair. Residents who want more than just a light bulb's worth of power can easily overload the system if they plug in too many appliances at once, the study found.

Even where systems work well, a few big chicken-and-egg problems remain, Aklin and other experts said.

For instance, if rural residents can't afford a refrigerator or sewing machine, their electricity use will remain extremely low. With low demand, banks and investors won't want to finance a larger, more expensive microgrid that might not deliver a profit. So residents are left with a smaller set-up that only allows for a few hours' worth of phone or light bulb use.

In another scenario, residents might have enough clean electricity to open a woodworking shop or a small textile business. But if the area has few job opportunities, the entrepreneurs will have few customers. A student could spend all night poring over her books, but if her school is failing, her education might not advance after all.

"Electrification is important, but it's not necessarily sufficient. It's only one part of the puzzle," said Josh Agenbroad, who is a manager of the Rocky Mountain Institute's Sustainable Energy for Economic Development program. Agenbroad works primarily on energy access issues in African countries, though he has toured microgrids in India's Uttar Pradesh state.

He said he believed that providing electricity through microgrids and other sources could boost rural development -- it just might not happen immediately.

"It takes time from when you provide light to when people are able to drive economic growth and change things," he said. "Some of these grids have been around for two to three years, and economies don't pop up overnight."