This article is more than 2 years old.

June 12, 2015 This article is more than 2 years old.

Solar energy has a surprising new supporter in India: The country’s massive state-owned railways.

India has one of the largest (pdf) railway networks in the world, running some 12,000 trains that carry over 23 million passengers every day. That’s almost as much as the entire population of Australia.

But moving such huge numbers of people—aside from transporting 3 million tonnes of freight daily—requires a massive amount of energy. In 2012, for instance, the Indian Railways consumed nearly 3 million kilolitres of diesel oil and about 14 billion kilowatt hours of electricity.

All that fuel costs a pretty penny— Rs30,000 crore ($4.7 billion) to be exact—that has, over time, begun hurting the balance sheet of the Indian Railways.

India’s railway minister, Suresh Prabhakar Prabhu, now wants the railways to control their ballooning fuel bill, even as the number of passengers and amount of freight increase. His plan: Incorporating more alternative energy sources to power trains.

By 2020, the Indian Railways is focusing on making renewable energy constitute at least 10% of its total energy consumption. And the first order of business in this ambitious plan is solar-powered lighting via panels mounted on the roofs of trains.

Indian Railways is currently testing this on a non-AC coach on the Rewari-Sitapur passenger train. The cost of installing the panels on each coach, according to the Economic Times, is about Rs3.9 lakh ($6,084), and these are expected to result in savings of Rs1.24 lakh ($1,934) per year.

Railway coach-maker Integral Coach Factory and the Indian Institute of Science, Bengaluru, will test out the solar-panelled coach in a variety of conditions in the coming weeks, according to The Hindu newspaper. Alongside the solar-powered coach, Indian Railways is also planning to build solar power plants in 200 train stations, as well as at some of its office buildings.

This solar energy push echoes prime minister Narendra Modi’s larger plan to encourage alternative energy as India remains among the top producers of carbon emissions, after China and the US. India’s solar power potential is about 750 gigawatts (pdf)—and the government is encouraging solar companies from around the world to invest $100 billion to reach its solar power capacity target of 100,000 megawatts by 2022. That’s about five times India’s current solar power generation capacity.

Modi has already led some interesting innovations in solar power. In Gujarat, for instance, the government commissioned solar panels over canals to minimise land use and prevent excess evaporation.

But pushing the massive Indian Railways towards going solar could be a much harder journey.