Monthly wholesale electricity prices and demand in New England, September 2018

Wholesale power and natural gas prices rose in September

Increased consumer demand for electricity, coupled with higher natural gas prices, pushed up average wholesale power prices for the month of September 2018 in both the Day-Ahead and Real-Time Energy Markets when compared to the previous year. The day-ahead energy price was up 43.8% to $33.89 per megawatt-hour (MWh)* and the real-time energy price rose 56.5% to $41.17/MWh.

Hotter-than-anticipated weather, and the corresponding rise in consumer demand, combined with unplanned generator outages to produce capacity scarcity conditions in the region on Sept. 3, 2018. Hourly average real-time energy prices rose over $2,400/MWh during these conditions at the New England Hub, a reference price for electric energy in the region.

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 48% of the power produced in 2017 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 $2.92 per million British thermal units (MMBtu)**. The price rose 55.3% from the September 2017 average Massachusetts natural gas index price of $1.88/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. The September average natural gas price recorded a 7% decrease from the August 2018 price of $3.14/MMBtu.

Electricity demand:

Demand is driven primarily by weather, as well as economic factors. Energy usage during September 2018 rose by 1.7% to 10,021 GWh from the 9,849 GWh used in September 2017. The average temperature during September was 66˚ Fahrenheit (F) in New England, the same as the previous September. The average dewpoint, a measure of humidity, was 59˚F in September 2018, up from 57˚F in September 2017. There were 79 cooling degree days (CDD)*** during September 2018, higher than the 51 CDD seen in September 2017. The normal number of CDD in September is 34 in New England. There were 76 heating degree days (HDD) during September 2018, higher than the 60 HDD seen in September 2017. The normal number of HDD in September is 88 in New England.

Consumer demand for electricity for the month peaked on September 6 during the hour from 3 to 4 p.m., when the temperature in New England was 90°F and the dewpoint was 71°. Demand reached 24,399 MW, with 26 MW met through reductions by active demand resources****. The September 2018 peak was 16.2% higher than the September 2017 peak of 20,999 MW, set during the hour from 4 to 5 p.m. on September 27, 2017, when the temperature was 84°F and the dewpoint was 69°.

Peak demand is driven by weather, which drives the use of heating and air conditioning equipment. 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°. 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°. 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 85% of the 8,699 GWh of electric energy generated within New England during September, at about 55.2% and 29.7%, respectively. Renewable resources generated about 9% of the energy produced within New England, including 5.6% from wood, refuse, and landfill gas; 2.3% from wind; and 1.1% from solar resources. Coal- and oil-fired units produced under 1%, combined, of the energy generated within New England. Hydroelectric resources in New England generated 5.5%. The region also received net imports of about 1,480 GWh of electricity from neighboring regions, and active demand response accounted for 3.9 GWh of reduced system demand.

September 2018 and Percent Change from September 2017 and August 2018
September 2018 Change from September 2017 Change from August 2018
Average Real-Time 
Electricity Price 
$41.17 +56.5% +5.1%
Average Natural Gas Price 
$2.92 +55.3% -7%
Peak Demand 24,399 MW +16.2% -6%
Total Electricity Use 10,021 GWh +1.7% -20.2%
Weather-Normalized Use***** 9,457 GWh -1.4% -16.6%
*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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