The share of electricity generated from coal in the U.S. during the first three months of this year was at its lowest first-quarter level in more than three decades—even though the overall total level of generation in the U.S. increased by a little less than 1%, the Energy Information Administration (EIA) reported last week.

The U.S. power sector generated nearly 440 TWh using coal during the first quarter of 2011—26.5 TWh less (or about 6% less) than the amount generated during the first quarter of 2010. Coal continued to dominate other generation sources, however, making up a 46% share of total generation.

The decline was pegged to increased generation by other sources—particularly natural gas. The EIA also attributed the decline to the steady rise of coal spot prices over two years—while natural gas prices remained comparatively low.

“This disparity in fuel costs has contributed to the decline in coal’s fuel share even in the Midwest Census Region [see map], where coal has historically been the dominant fuel used in the electric power sector,” the EIA said. “During the first quarter of 2011, coal’s share of generation in the Midwest fell from 70.5% in 2010 to 66.9%, while the region’s fuel share for natural gas gained 2 percentage points.”

Coal-fired generation also plunged in the South, falling from 54.5% during the first quarter of 2008 to 47.7% during the same period this year. According to the federal information body, the Northeast and West, regions that are much less dependent on coal, showed first-quarter 2011 coal shares of 24.9% and 29.0% respectively. This reflected a decrease of 8.0 percentage points in the Northeast and 2.6 percentage points in the West from the same period in 2008.

However, preliminary estimates for the second quarter of this year showed an increase in coal-fired generation, the EIA said. This was mostly because this spring, the number of nuclear power plant outages was much higher than the seasonal norm, and coal plants were required to meet baseload demand.

“Total nuclear outages were higher in 2011 than any of the previous four years for much of April, May, June and into July,” the EIA said, adding that this was likely because the refueling season coincided with several forced outages and weather-related decreases in capacity availability.

“The industry marked a ten-year high in total outages in early May 2011 with the loss of Tennessee Valley Authority’s (TVA’s) three Browns Ferry units (almost 3.5 gigawatts) due to tornado damage to transmission lines serving the plant,” it said. The Browns Ferry units remained below full capacity through May 28, but outages of TVA plants accounted for 11% of total outages from April through June.

Sources: POWERnews, EIA