Oil becomes the main fuel for power plants in the eastern U.S.

The power grid of six eastern U.S. states used oil to generate at least one-third of their electricity, and in some cases as much as 40%, according to ISO New England. Meanwhile, natural gas provided about 15%.

Oil is a reserve source for the regions, which is usually resorted to in extreme cases to meet the demand for electricity during the hottest and coldest days of the year. In New England, market participants were urged to save electricity due to a likely lack of stocks.

The situation is heated to such an extent that prices reached the level of $2,000 per megawatt-hour on Saturday night. Last week, spot price was around $30.

While New England is likely to be in shortage conditions throughout the winter, the fact that oil has overtaken gas, nuclear and hydropower may speak to the severity of the current season's situation.