Modi, who last month imposed a three-week long nationwide lockdown, asked citizens to turn out their lights for nine minutes at 9pm on Sunday and to display lamps and candles in a show of solidarity.
People across the country switched off lights. Some lit firecrackers, played drums, clapped and chanted slogans against the coronavirus.
In some big cities like Mumbai and New Delhi, residents of some housing associations stood in balconies and sang patriotic songs.
Many of Modi's supporters praised the "show of lights" by sharing pictures on Twitter of their neighbourhoods and saying it felt like Diwali - the annual Hindu festival of lights.
But the prime minister's call also drew criticism from people who called for steps to help millions of daily wage earners squeezed out of a living amid the lockdown, which was imposed nationwide on March 25. "Only a brain-dead country can celebrate with lights and firecrackers at the time of a pandemic, while millions are jobless and hungry and in real fear of death," a Twitter user with the handle @ashoswai said.
India's Power System Operation Corp (POSOCO), which oversees the national power grid, had ordered all senior officials to be present at generating stations, substations and load despatch centres across India between 6 p.m. and 10 p.m. on Sunday.
The country's electricity demand fell more than 25% to 85.3 gigawatt (GW) from 117 GW within a span of four to five minutes as people switched off lights, said Power Minister RK Singh, adding the transition was handled smoothly by engineers.
India's power consumption has already plunged over the last 10 days, as the lockdown has forced most industries to suspend operations.