October 25, 2021

Monthly wholesale electricity prices and demand in New England, September 2021

Prices up in both day-ahead, real-time markets in September

Wholesale power prices averaged $46.76 per megawatt-hour (MWh)* in the Real-Time Energy Market in September 2021, up 135% compared to the previous year. Day-Ahead Energy Market averages rose to $48.01/MWh, which was also an increase of 135% from September 2020.

By the numbers

September 2021 and Percent Change from September 2020 and August 2021	September 2021	September 2020	August 2021
Average Real-Time Electricity Price *($/megawatt-hour)**	$46.76	135.2%	-4.4%
Average Natural Gas Price ($/MMBtu)**	$4.43	207.6%	12.7%
Peak Demand	20,005 MWs	3.9%	-20.5%
Total Electricity Use	9,628 GWh	4.3%	-20.2%
Weather-Normalized Use*****	9,445 GWh	2.8%	-15.2%

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 52% of the power produced in 2020 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 September was $4.43 per million British thermal units (MMBtu)**. The price was up 208% from the September 2020 average Massachusetts natural gas index price of $1.44/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.

September wholesale electricity and natural gas prices

Electricity demand

Demand is driven primarily by weather, as well as economic factors. Energy usage during September increased 4.3% to 9,628 GWh from the 9,233 GWh used in September 2020. The average temperature during September was 66˚ Fahrenheit (F) in New England, up 2˚ from the previous September. The average dewpoint, a measure of humidity, was 58˚F in September, down 5˚ from the previous September. There were 43 cooling degree days (CDD)*** during September, while the normal number of CDD in September is 33 in New England. In September 2020, there were 34 CDD. There were 32 heating degree days (HDD)*** during September, while the normal number of HDD in September is 89 in New England. In September 2020, there were 85 HDD. ISO New England is publishing weekly reports on the estimated impact on electricity demand of societal changes in response to the COVID-19 pandemic.

Consumer demand for electricity for the month peaked on September 15 during the hour from 4 to 5 p.m., when the temperature in New England was 82°F and the dewpoint was 69°. Demand reached 20,005 MW. The September 2021 peak was 3.9% higher than the September 2020 peak of 19,260 MW, set during the hour from 5 to 6 p.m. on September 10, when the temperature was 77°F and the dewpoint was 71°.

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°. 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°. 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.

September monthly peak demand and total and weather-normalized energy use

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 83% of the 8,680 GWh of electric energy generated within New England during September, at about 56% and 27%, respectively. Renewable resources generated about 11% of the energy produced within New England, including 5.4% from wood, refuse, and landfill gas; 2.9% from wind; and 2.9% from solar resources. Hydroelectric resources generated 5.4%. Coal and oil-fired resources each generated less than one-tenth of one percent. The region also received net imports of about 1,812 GWh of electricity from neighboring regions.

September generation in New England, by fuel source

_{*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 1,000 homes for one hour. One gigawatt-hour (GWh) can serve about 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.}