Monthly wholesale electricity prices and demand in New England, December 2019

Real-time electricity prices up, day-ahead prices down in December

Average wholesale power prices in December 2019 were up 2.2% in the Real-Time Energy Market when compared to the previous year, rising to $42.77 per megawatt-hour (MWh)*. Prices, however, were down by 13.4% in the Day-Ahead Energy Market when compared to December 2019, averaging $40.98/MWh.

Drivers of wholesale electricity prices

In general, the two main drivers of wholesale electricity prices in New England are the cost of fuel used to produce electricity and consumer demand.

Power plant fuel: Fuel is typically one of the major input costs in producing electricity. Natural gas is the predominant fuel in New England, used to generate 49% of the power produced in 2018 by New England’s power plants, and natural gas-fired power plants usually set the price of wholesale electricity in the region. As a result, average wholesale electricity prices are closely linked to natural gas prices.

The average natural gas price during December was $4.71 per million British thermal units (MMBtu)**. The price fell 17.7% from the December 2018 average Massachusetts natural gas index price of $5.72/MMBtu. The Mass. index price is a volume-weighted average of trades at four natural gas delivery points in Massachusetts, including two Algonquin points, the Tennessee Gas Pipeline, and the Dracut Interconnect.

Electricity demand: Demand is driven primarily by weather, as well as economic factors. Energy usage during December rose by 1.1% to 10,652 GWh from the 10,539 GWh used in December 2018. The average temperature during December was 33˚ Fahrenheit (F) in New England, down one degree the previous December. The average dewpoint, a measure of humidity, was 23˚F in December, the same as December 2018. There were 995 heating degree days (HDD)*** during December, while the normal number of HDD in December is 979 in New England. In December 2018, there were 976 HDD.

Consumer demand for electricity for the month peaked on December 19 during the hour from 5 to 6 p.m., when the temperature in New England was 18°F and the dewpoint was 1°. Demand reached 19,033 MW, with 30 MW met through reductions by active demand resources****. The December 2019 peak was 3.1% higher than the December 2018 peak of 18,466 MW, set during the hour from 5 to 6 p.m. on December 18, when the temperature was 27°F and the dewpoint was 10°.

Peak demand is driven by weather, which drives the use of heating and air conditioning equipment. The all-time high winter peak was 22,818 MW, recorded during a cold snap in January 2004 when the temperature was -1°F and the dewpoint was -20°F. The all-time peak demand in New England was 28,130 MW, recorded during an August 2006 heat wave, when the temperature was 94°F and the dewpoint was 74°F. Air conditioning use is far more widespread than electric heating in New England, so weather tends to have a relatively greater impact on the summer peak than the winter peak.

Fuel mix: The mix of resources used in any given time period depends on price and availability, as well as supplemental resource commitments needed to ensure system stability. Natural gas-fired and nuclear generation produced about 78% of the 8,376 GWh of electric energy generated within New England during December, at about 51% and 27%, respectively. Renewable resources generated about 12% of the energy produced within New England, including 6.7% from wood, refuse, and landfill gas; 4.9% from wind; and 0.6% from solar resources. Coal- and oil-fired units produced approximately 1% combined of the energy generated within New England. Hydroelectric resources generated 9%. The region also received net imports of about 2,394 GWh of electricity from neighboring regions, and active demand response accounted for 4 GWh of reduced system demand.

December 2019 and Percent Change from December 2018 and November 2019
December 2019 Change from December 2018 Change from November 2019
Average Real-Time 
Electricity Price 
$42.77 +2.2% +24.8%
Average Natural Gas Price 
$4.71 -17.7% +40.6%
Peak Demand 19,033 MW +3.1% +8.7%
Total Electricity Use 10,652 GWh +1.1% +12.9%
Weather-Normalized Use***** 10,621 GWh +0.7% +15.1%
*One megawatt (MW) of electricity can serve about 750 to 1,000 average homes in New England. A megawatt-hour (MWh) of electricity can serve about 750 to 1,000 homes for one hour. One gigawatt-hour (GWh) can serve about 750,000 to 1 million homes for one hour. **A British thermal unit (Btu) is used to describe the heat value of fuels, providing a uniform standard for comparing different fuels. One million British thermal units are shown as MMBtu. ***A degree day is a measure of heating or cooling. A zero degree day occurs when no heating or cooling is required; as temperatures drop, more heating days are recorded; when temperatures rise, more cooling days are recorded. The base point for measuring degree days is 65 degrees. Each degree of a day’s mean temperature that is above 65 degrees is counted as one cooling degree day, while each degree of a day’s mean temperature that is below 65 degrees is counted as one heating degree day. A day’s mean temperature of 90 degrees equals 25 cooling degree days, while a day’s mean temperature of 45 degrees equals 20 heating degree days. ****Since June 1, 2018, active demand-response resources have been able to participate on an hourly basis in the wholesale electricity markets. These resources reduce demand in real time.*****Weather-normalized demand indicates how much electricity would have been consumed if the weather had been the same as the average weather over the last 20 years.

Historical weather data provided by DTN, LLC.; Underlying natural gas data furnished by ICE


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