NEW DELHI — A power failure cut service to 370 million people in northern India for up to 15 hours Monday, halting trains, forcing hospitals and airports onto backup power, and providing a dark, sweltering reminder of the nation’s inability to meet its energy needs as its economy grows.
While the outage was unique in its reach — more than the population of the United States and Canada combined — its impact was softened by Indians’ familiarity with almost daily blackouts of varying duration. Hospitals and major businesses have backup generators, as do upscale homes.
Nonetheless, some small businesses were forced to shut for the day. Buildings were without water because the pumps weren’t working, and the vaunted New Delhi Metro, with 1.8 million daily riders, was paralyzed during the morning commute.
‘‘This will obviously get worse,’’ said Subhash Chawla, a 65-year-old retiree who took the Metro once power was restored. “Unless the Metro has a separate power supply, it will be chaos in the future.’’
The grid that failed feeds the nation’s breadbasket in Punjab, the war-wracked region of Jammu and Kashmir, the burgeoning capital of New Delhi, the Dalai Lama’s Himalayan headquarters in Dharmsala, and the world’s most populous state, poverty-stricken Uttar Pradesh. The power failure also affected businesses and households in the states of Haryana, Himachal Pradesh, and Rajasthan.
Many areas had power back in less than nine hours. By evening, 15 hours after the outage began, officials said full power had been restored.
The outage left millions sweltering in summer heat. Muslim families had to eat predawn meals by candlelight before beginning their daytime Ramadan fast.
The Confederation of Indian Industry said the outage was a reminder of the urgent need for the government to fix the power sector, ensure a steady supply of coal for power plants, and reform the electric utilities. Transmission and distribution losses in some states are as much as 50 percent because of theft and corruption.
Power Minister Sushil Kumar Shinde deflected criticism, pointing out that the United States and Brazil also had huge power failures in recent years. “I ask you to look at the power situation in other countries as well,’’ he said.
The blackout, the worst to hit India in a decade, began about 2:30 a.m. Officials in Uttar Pradesh, where the problem was believed to have begun, said the grid could not keep up with the huge demand for power in the hot summer.
But Shinde said he was not sure what caused the collapse and had formed a committee to investigate.
More than 100 trains were stranded when their electric engines failed. Others were delayed for hours as they were hooked to diesel engines.
The failure was the first time since 2001 that the northern grid collapsed. But India’s demand for electricity has soared since then as its population and economy have grown sharply.
But any connection to the grid remains a luxury for many. One-third of India’s households do not even have electricity.
The power deficit was worsened by a weak monsoon that lowered hydroelectric generation and kept temperatures higher, further increasing electricity usage as people sought to cool off. Shivpal Singh Yadav, the power minister in Uttar Pradesh, home to 200 million people, said that while demand during peak hours hits 11,000 megawatts, the state can provide only 9,000 megawatts.
Uttar Pradesh Power Corp. chief Avnish Awasthi blamed the grid collapse on states drawing more than their allotted power. The Nuclear Power Corp. of India’s five units in Rajasthan shut down after the outage, officials said. It is expected to take up to 36 hours to restore the units.
Prime Minister Manmohan Singh has been trying to secure $400 billion of investment in the power industry in the next five years as he targets an additional 76,000 megawatts in generation by 2017. India has missed every annual target to add electricity production capacity since 1951.
Power cuts are common across large sections of India. The country faces an average 9 percent shortfall in meeting peak power demand, which the government says shaves about 1.2 percentage points off annual economic growth. The affected states are responsible for about 37 percent of electricity consumption, according to the Central Electricity Authority.
Improving infrastructure, which the World Economic Forum says is a major obstacle to doing business in India, is among the toughest challenges facing Singh as he bids to revive expansion in Asia’s third-largest economy; it slid to a nine-year low of 5.3 percent in the first quarter.