The deal will make Reliance Power -- controlled by billionaire Anil Ambani, the younger brother of India's richest man Mukesh Ambani -- the largest private provider of hydroelectric power in India, the firm's statement said.
Reliance has signed a memorandum of understanding to buy the three plants, the entire hydropower business of Jaiprakash, which is part of the Delhi-based conglomerate the Jaypee Group.
The plants will produce nearly 1,800 megawatts of clean energy for Reliance Power, part of the Ambani's Reliance Group, whose empire includes telecommunications and financial services.
The companies did not disclose details of the deal, but one source said Reliance would pay about 120 billion rupees ($2.0 billion), while a local business newspaper said the figure was around $2.5 billion.
The deal follows the collapse last week of an attempt by an Abu Dhabi-led consortium to buy two of the plants for about $1.6 billion, according to local reports.
The Reliance deal comes at a time when many major coal-fired power stations in India are facing possible shutdown because of an acute shortage of the fossil fuel.
India's new government has pledged to boost power and electricity output to meet growing demand from businesses and household consumers and help kickstart the ailing economy.
Blackouts, particularly during peak summer months, are common across vast swathes of India, crimping production.
Shares in Reliance Power were up 2.53 percent at 93.15 rupees, while Jaiprakash Power Ventures rose 4.49 percent to 19.80 rupees on the Bombay Stock Exchange.