OREANDA-NEWS. Coal-fired power plants operated by major southwest utilities generated more electricity in June than a year earlier, bucking the trend in other coal-reliant US power grids.

Output by southwest coal plants averaged 1.1pc higher year over year to an average of 5,081MW in the Southwest Variable Energy Resource Initiative members' territories, which cover most of Arizona and New Mexico and parts of neighboring states. Coal accounted for 38pc of total generation and its share was unchanged from June 2014.

Natural gas accounted for 32pc of generation, up from a 29pc share a year earlier. Output by gas-fired power plants in absolute terms increased by 13pc. Nuclear and renewable resources produced less electricity than a year earlier.

Coal burn in the southwest was higher as power demand increased. Average load in June was up by 4.1pc and generation increased by 2.7pc. Cooling degree days in Arizona and New Mexico in June exceeded year-earlier levels and seasonal norms, according to the National Weather Service.

Powder River basin (PRB) accounts for the bulk of external supply for the power plants in the region although many utilities there operate mine-mouth generators. Prompt-quarter delivered PRB prices in the past month were 7pc lower than a year earlier. Natural gas prices fell by a larger proportion.

The Southwest Variable Energy Resource Initiative aggregates load and generation data from eight utilities: Arizona's Generation and Transmission Cooperatives, Arizona Public Service, El Paso Electric, California's Imperial Irrigation District, Public Service of New Mexico, Salt River Project, Tucson Electric Power and the Western Area Power Administration's desert southwest region.

Coal-fired generation in those utilities adds up to more than 11GW. About 1GW of that capacity will retire in 2016-17, including units at the Cholla plant in Arizona and San Juan Generating Station in New Mexico, according to Argus' power plant retirement database.

Coal plants last year accounted for 26pc of installed capacity and 39pc of total generation in the southwest.