U.S. energy firms posted lower earnings in the first quarter of 2009 Tuesday, affected by the global economic slowdown which has reduced power demand across the nation.

Electricity consumption is expected to decline 2 percent in the U.S. this year, and industrial sales are forecasted to slump 6.4 percent, according to the Energy Information Administration in March. Demand for energy usually increases 1 to 2 percent a year.

Duke Energy, one of the largest power providers in the U.S., reported its net income fell 26 percent to $344 million or 27 cents a share, from $465 million or 37 cents a share in the same period a year ago, as sales to industrial customers fell, operating and maintenance expenses increased, and damage from from storms, the company said.

Analysts expected earnings of 32 cents a share, according to a FactSet Research poll.

Spectra Energy's net income fell 19 percent to $298 million or 47 cents a share, compared to $367 million or 58 cents a share in the same period of 2008.

Constellation Energy reported a first quarter loss of $123.5 million or 62 cents a share, compared with $145.7 million or 81 cents in the same quarter a year earlier.

Analysts expected earnings of 64 cents a share according to a FactSet survey.

Progress Energy net income was $182 million or 66 cents down from $209 million or 80 cents a share in the same period of the year ago.

First Energy net income dropped far below forecasts to $115 million or 39 cents a share from $227 million or 90 cents a share in the same period of 2008. Analysts expected earnings of 91 cents, according to FactSet.

Sempra Energy's earnings rose 40 percent to $316 million or $1.29 per diluted share, compared to $242 million the year ago period.

The Dow Jones Utilities Average closed 0.37 percent down to 346.04 points on Tuesday.