It depends on your consumption and the rooftop area. You can easily calculate it on: https://solarrooftop.gov.in/rooftop_calculator. The Central Government also provides 30% subsidy on it. A solar installation costs anything between Rs 40,000 and Rs 600,000, depending on your consumption.
Net metering allows you to send the surplus power, whenever your consumption is low, to the electricity grid. This gets adjusted in your monthly bill cycle. Say, if your monthly consumption is 1,000 KwH, and your panel has sent 400 KwH to the grid, you will be charged only for 600 KwH. This way you earn a credit from power discoms in your electricity bill. In case, power from solar panels exceeds your monthly consumption, the discom will pay you.
The major issue here is the initial investment. The income, however, is hidden in the savings one makes in the monthly billing cycle. The amount invested in a solar panel can easily be recovered in 3-5 years through reduced electricity bills.
Even if you do not have immediate capital to invest in a solar power installation, there are companies that will finance you. They will install the system at your home, and for every unit of electricity the system generates, you will have to pay the company. The price per unit will be lower than what you pay to the power discoms.
India has planned to generate 100 Gw of solar power by 2022. Experts feel the target would be difficult to achieve. You can help India reach this goal and reduce its energy dependence from fossil fuels by installing solar rooftops, which is a smart investment, giving one enough savings on electricity bills.