Most of India's coal-fired power plants have critically low levels of coal inventory at a time when the economy is picking up and fueling electricity demand.

By comparison, over the last four years, the average coal inventory that power plants had was around 18 days worth of supply, according to Hetal Gandhi, director of research at ratings firm CRISIL, a subsidiary of S&P Global.

Thermal power companies have had lean coal inventories and did not anticipate the spike in power demand this year, Gandhi explained.

Logistical issues due to the monsoon season also constrained coal supply, despite there being enough pithead stocks available at Coal India, Sandeep Kalia, principal analyst at Wood Mackenzie, told CNBC. .

However, a widening gap between soaring international coal prices and domestic coal prices saw imports decline sharply in recent months.

Coal imports by power plants fell 45% in July and August compared to the same period last year while India's non-power sectors grew more dependent on domestic coal, Kalia said.

"Whenever imported prices go up substantially, the incentive for domestic manufacturers to import coal and produce power is on the lower side," she said.

"The coal available at the power plants is a rolling stock which gets replenished by the supplies from the coal companies on a daily basis," the ministry said

In fact this year, domestic coal supply has substituted imports by a substantial measure."

"Given India's massive dependence on thermal power, we might see domestic coal suppliers diverting their supply to the thermal power plants away from industries like steel, cement etc," Societe Generale's Kundu told CNBC by email