Electricity demand and natural gas prices were the majordrivers of power prices in September, as U.S. power prices were mixed andgeneration margins were in line with year-ago levels.
Average day-ahead market on-peak power prices in the U.S. averaged$33.56/MWh, up 0.4% versus the prior year. The New York ISO saw the largestdrop in DAM on-peak power prices, as they fell 12.5% to $31.98/MWh versus theyear-ago month on lower natural gas prices and falling electricity demand.Meanwhile, natural gas prices and demand headed the opposite direction in ERCOTto drive power prices 12.7% higher year over year to $33.08/MWh.
In the New York ISO, average load was down 3.1% and peakload was down 4.6% year over year, while ERCOT saw average load climb 2.6% overthe same period and peak load jump 3.8% to 66,887 MW.
Meanwhile, natural gas prices serving the New York ISOaveraged $2.461/MMBtu, down 12.5% year over year, as those serving all U.S.markets climbed 3.3% to $2.735/MMBtu. ERCOT saw natural gas prices jump 12.4%to $2.908/MMBtu.
Despite widely diverging trends, ERCOT and NYISO saw naturalgas-fired implied heat rates — the efficiency rate at which the market cost ofpower equals the cost of burning natural gas to generate power — that werenearly flat to the year-ago period.
Meanwhile, diverging domestic thermal coal price trendsdrove changes in coal-fired implied heat rates. During September, prompt-monthCentral Appalachian barge-delivered coal prices climbed 4% during the month to$41.88/ton, while the region's rail-delivered coal prices jumped 21.7% over thesame period to $56/ton on strengthening seaborne coal prices. September averageprices for barge-delivered coal were down 3% year over year while those ofrail-delivered coal jumped 17.6% over the same period. Around-the-clock,day-ahead market power prices averaged $28.87/MWh for a 1.3% year-over-yeardecline, leading U.S. average implied heat rates for barge-delivered coal toedge 0.8% higher year over year, while those of rail-delivered coal fell 11.8%over the same period.
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