• City in midst of heat wave expected to last through Thursday
  • Local power demand climbing to power air conditioners

The first clouds of a thunderstorm had yet to darken the skies above New York and it was already wreaking havoc on the city’s wholesale power prices Monday.

Spot electricity catapulted to $1,042.37 a megawatt-hour at 3:25 p.m., from less than $50 earlier in the day. The agency that oversees New York’s power system issued an alert in advance of the storm that cut the amount of electricity allowed to be carried across transmission lines feeding the city, energy data provider Genscape Inc. said.

Usually, starting up local generation can quickly ease price spikes. New York, however, is on day five of a heat wave that’s expected to last through Thursday, and backup oil-fired plants in the city are already online to help power air conditioners. So curtailing supplies is adding sparks to a power market that had, until Monday, been humming along quietly as New Yorkers boiled with the rising temperatures.

The grid operator is “worried about lightning hitting between Albany and NYC” and knocking out import lines, said Ben Chamberlain, a Boston-based analyst with Genscape. “More local generation would help, but I think they’re running almost everything already.”

Blue, sunny skies over Manhattan quickly gave way to dark clouds about 4 p.m., followed quickly by sheets of rain, hail and thunder.

The grid operator’s thunderstorm alert issued two hours earlier came after electricity imports from Canada plunged. The New York ISO reported it had four large reserve pickups for seven minutes starting at 1:38 p.m., which Chamberlain said can signal that there was a sudden supply outage. 

Power flows on Hydro-Quebec’s Chateauguay high-voltage transmission line that feeds New York dropped to 300 megawatts at 2:10 p.m. from 1,500 megawatts 1:35 p.m., grid and Genscape data show. A spokeswoman for Hydro-Quebec couldn’t be immediately reached for comment.

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