(Bloomberg) -- New York City electricity prices soared to a four-year high as the coldest day so far this winter spurs heating demand and natural gas costs rise. 

The average price for on-peak power on Tuesday jumped 36% to $222.97 a megawatt-hour, the highest since Jan. 5, 2018, according to grid data compiled by MCG Energy Solutions. The price for natural gas, the leading power-plant fuel in the state, was the highest for this time of year since 2017. 

Most power used on a given day is secured in the day-ahead market. Demand was recently coming in about 5% above those forecasts. So spot prices are also strong, averaging about $200 since 7 a.m. and briefly spiking to almost $948, according to the New York Independent System Operator website. 

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