When a sweeping power failure blacked out 700 million people in India last July, the cell sites that connect nearly one billion mobile phone users in the country were largely unaffected.

The vast majority of Indian cell-phone base stations, which each include a tower and radio equipment attached to it, had backup diesel power because the electricity goes out frequently, and many run on diesel entirely if there is no power grid in the area at all. Now dirty diesel generators in India are being challenged by clean, renewable energy, and the movement has implications for other developing nations that also have incomplete or unreliable electric networks. Even in developed nations with reliable electricity, changes in the structure of mobile networks could open the door for alternative energy.

In India, which has about 400,000 base stations, the government has mandated that 50 percent of rural sites be powered by renewables by 2015. The decision comes as the Indian government, which heavily subsidizes diesel, looks to lessen the country’s reliance on foreign oil and reduce greenhouse gas emissions. By 2020 75 percent of rural and 33 percent of urban stations will need to run on alternative energy.

The move by the world’s second-largest mobile market after China will likely drive down the price of renewable-powered base stations for other regions with low electrification rates, such as sub-Saharan Africa, according to Mrinmoy Chattaraj, a campaigner with Greenpeace India’s Climate and Energy Unit.

“It’s been a slow rate of adoption,” Eric Woods, research director with Pike Research, says of the telecom industry’s uptake of renewables to date. “But India’s deployment will have an impact across the developing world. It’s moving the market away from the default position of using diesel.”

There are about five million cell phone towers worldwide, 640,000 of which aren’t connected to an electrical grid and largely run on diesel power. One study estimated that 75,000 new off-grid towers would be established in 2012 alone.

The Indian telecom industry consumed an estimated 3.2 billion liters of diesel in 2011, and the amount could rise to six billion liters by 2020, according to Greenpeace India. Enforcement of new regulation would save more than 540 million liters of diesel annually and cut about nine million tons of carbon emissions by 2015.

Diesel prices have nearly tripled in the past twelve years in India, to about 80 cents per liter in July 2012. The price is expected to increase further with diesel deregulation, according to Chattaraj, as solar technologies become cheaper. Today, solar installations with battery backups are more expensive to install upfront, but the yearly operational expenditure is far lower, recouping the investment in about two to four years. The current annual cost to run a diesel generator for a base station is about $14,510 in India, compared with $8,215 for solar with battery backup. By 2020 the annual cost of using diesel is expected to be more than $20,000 whereas the cost of solar and batteries will likely fall to less than $5,500.

Renewable options also become much more viable as the amount of energy needed to power base stations is reduced. The average cellular base station, which comprises the tower and the radio equipment attached to it, can use anywhere from about one to five kilowatts (kW), depending on whether the radio equipment is housed in an air-conditioned building, how old the tower is and how many transceivers are in the base station. Most of the energy is used by the radio to transmit and receive cell-phone signals. On the low end, a tower that runs all the time uses about the same energy annually as an average U.S. household. Many of the off-grid stations, however, use closer to five kW, according to Pike Research, a market research firm that covers global clean-tech markets.

Solar dominates as an alternative to diesel because of cost, but Indian telecoms are also exploring aggregated renewable solutions (wind and solar, for example), fuel cells and bio-CNG digesters to power base stations. “They’re already giving diesel a run for its money,” Chattaraj says of the various clean energy solutions in India. But there is still a long way to go; Chattaraj notes that only about 9,000 towers have switched to alternative energy, a figure mandated to rise to 80,000 by 2015.

India’s directive could have the greatest impact on Africa, according to Chattaraj, where many countries have less than half of their towers connected to an electric grid. Chattaraj says that Greenpeace is already working in South Africa to produce a report similar to the one that helped bring the issue to the forefront in India. Programs by cellular networks, like Groupe Speciale Mobile Association’s (GSMA) Green Power for Mobile, are also trying to advance the use of renewables in off-grid locations.

In the U.S., which has an estimated 285,000 cell sites, less than 1 percent are powered by renewables, but that figure is slowly increasing. Verizon has about 20 solar-powered base stations. T-Mobile, one of the earliest big carriers to switch on a fully solar-powered cell site in 2011, has added renewables to more sites and sometimes uses solar energy as temporary backup power, a practice that the company said it will expand in the coming years.

One company that supplies solar generators to two of the major carriers (DC Solar) said that the move from diesel to solar generators, whether for planned maintenance or if after-storm damage cuts off grid power, is catching on as more providers become aware of the option and because it costs about 30 percent less. “I think the biggest thing is that the technology is now proven,” says Paulette Carpoff, vice president and owner of DC Solar Solutions.

Globally, the focus is on efficiency and low-power components, especially as bandwidth requirements strain networks. Lowering the energy needs of base stations could also help spur the adoption of renewables. “Energy efficiency is one way to make renewables economically viable,” says Thierry Klein, head of green research at Alcatel–Lucent’s Bell Labs.

The industry is working on more integrated chip technology and smaller radios to improve energy efficiency, including units that can turn themselves off when not in use. Alcatel–Lucent is also integrating energy monitoring capability into base stations, which can be used to make real-time adjustments to optimize power use and monitor renewables.

If the architecture of mobile networks moves to smaller, more distributed small cells, renewable power could be more attractive in developed and developing countries. Employing smaller cells is a growing movement in the mobile phone industry, which uses much smaller antennas and radios that in turn use far less energy yet allow carriers to increase network capacity. Klein noted that cost of digging and trenching to run power lines to cell sites can be a large part of the cost for stations connected conventionally to an electric grid, and running extra wires to many, very small sites might not be feasible.

“In the future,” Klein says, “if the carriers move to more small cells, you will need to install more renewables.”