If the north had to sweat it out on Monday, it was mostly the south’s turn the day after.

Many parts of south Calcutta suffered rotational power cuts for 60-90 minutes on Tuesday as snags in the CESC network and inferior coal used by the state utility came in the way of meeting the demand.

Among the worst-hit were ICSE examinees. “Frequent power cuts affect our last-minute preparations,” said Vikramjeet Roy, who will write his ICSE chemistry paper on Wednesday.

Kalighat resident Suparna Basu, 32, said: “There was no power in our neighbourhood for nearly two hours this afternoon. If the situation is so dismal now, what will happen when the summer is at its peak?”

A CESC official said a “transient fault caused by a tripping” resulted in a 15-minutes power cut in parts of south Calcutta in the afternoon. For the remaining duration of the disruption, the official blamed the state utility.

A power department source said shortage of good-quality coal had “severely affected” generation by the state power development corporation. “The coal supply is likely to normalise by Friday and we’ll be able to generate optimum power by the weekend.”

The peak-hour shortfall in the CESC-served areas was around 90MW and the places served by the state utility reeled under a deficit of 550MW.

CESC sent out 1,155MW against the peak-hour demand of 1,400. Part of the deficit was met with supply from the state grid. “There has been a 6-8 per cent growth in demand, on a year-on-year basis. From around 1,300MW during this time last year, the demand has risen to 1,400MW or so,” said a company spokesperson.

Power department officials attributed the spurt in demand to the growing number of air-conditioners in the city.

“Not only has the number of air-conditioners gone up substantially but also their use in early March, which is technically spring and when the weather is expected to stay pleasant,” an official explained.

“I was planning to buy an air-conditioner in April or May but I bought it last week because of the early onset of summer,” said 26-year-old techie Avishkar Bose, a Lake Town resident.