Northern India's power grid crashed Monday, halting trains, forcing hospitals and airports onto backup power and providing a dark reminder of the country's inability to feed a growing hunger for energy as it strives to become an economic power.

While the midsummer outage was unique in its reach — it hit 370 million people, 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 that seamlessly kick in during power cuts, and upscale homes are hooked to backup systems powered by truck batteries.

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 busy 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 feeds the country's breadbasket in Punjab, the war-wracked region of 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, with its 200 million residents.

By late morning, less than nine hours after the outage started, most of the affected areas had their power back, officials said.

By evening, 15 hours after the outage began, officials said full power had been restored.

Theft and corruption

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 electricity utilities.

Transmission and distribution losses in some states are as much as 50 per cent because of theft and corruption by employees in the power industry. India's Central Electricity Authority reported power deficits of about eight per cent in recent months.

Passengers on an idle train wait for electricity to be restored at a railway station in the northern Indian city of Allahabad on Monday. (Jitendra Prakas/Reuters)

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. when the grid covering eight northern states crashed. 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. Temperatures in New Delhi were in the mid-30s.

But Shinde said he was not sure exactly what caused the collapse and had formed a committee to investigate.

As officials struggled to get the grid back on line, they drew power from the neighboring eastern and western grids as well as hydroelectric power from the small neighbouring mountain kingdom of Bhutan.

Some trains across the northern region were stranded when their electric engines failed. Others were delayed by hours as they were hooked to diesel engines.

The failure was the first time since 2001 that the northern grid had collapsed. But India's demand for electricity has soared since then as its population and economy have grown sharply.

Any connection to the grid remains a luxury for many. One-third of India's households do not even have electricity to power a light bulb, according to last year's census.