Summer 2022—Weather Challenges and Risks to Electric Power

Summer 2022—Weather Challenges and Risks to Electric Power

INSIGHTi

Summer 2022—Weather Challenges and Risks
to Electric Power
June 29, 2022
The 2022 summer season has arrived, and with warmer weather, the demand for electricity to cool
residences and buildings generally increases across the country. According to the U.S. Climate Extremes
Index (CEI), during summer months (June-August) there has been an increasing trend in the percentage of
the contiguous United States with maximum temperatures much above normal over the last 30 years
(Contiguous U.S., Summer—extremes in maximum temperature: step 1). Further, over the same
timeframe, during summer months (June-August), the percentage of the contiguous United States with
minimum temperatures much above normal has also increased (Contiguous U.S., Summer—extremes in
minimum temperature: step 2). This summer has been held out by the North American Electric
Reliability Corporation as one that may be especially challenging for electric power generation in several
U.S. regions in its 2022 Summer Reliability assessment, due to the ongoing drought in the southwest and
other factors. With a spate of recent older coal power plant retirements, electric utilities will place a
greater reliance on natural gas and renewable electric sources for power generation. Coal, nuclear, natural
gas and some renewable resources can be challenged to perform efficiently in the warmer summer
months.
Generation Efficiency, Cooling, and Performance
Power generation in the summertime comes with some very specific challenges, as atmospheric
conditions can impact overall efficiency. Most power plants (i.e., base load generation such as fossil fuel-
fired power, some geothermal, and nuclear power plants) operate on a steam-electric cycle where water is
heated turning it into steam to drive a turbine-generator. The steam exiting the turbine has to be
condensed and cooled before it can be recycled to generate more electricity. While some power plants use
rivers or other large bodies of water to cool the condensed steam (i.e., “direct once through” wet cooling),
other power plants use cooling towers where air passing through the exiting steam cools the water by
evaporation. Cooling the water is important for steam-electric cycle efficiency, as colder water provides
more efficient power generation. The efficiency of evaporative cooling towers depends largely on the
ambient wet bulb temperature, since evaporative cooling towers generally provide cooling between 5
degrees to 7 degrees Fahrenheit above the ambient wet bulb temperature. This means that cooling tower
Congressional Research Service
https://crsreports.congress.gov
IN11964
CRS INSIGHT
Prepared for Members and
Committees of Congress

Congressional Research Service
2
efficiency is generally lower on warmer days than it would be on cooler days. Warmer summer
temperatures can therefore result in lower power plant power generation efficiency and output, especially
on humid days.
Elevated air temperatures can also decrease the capacity of transmission cables to carry electricity. The
effects of ambient temperature on electric transmission capacity are well known, but electric utilities
typically base transmission system ratings on historical temperature profiles. However, to increase
existing electric transmission line capacity, the Federal Energy Regulatory Commission recently issued an
order allowing transmission lines to operate closer to their thermal capacity ratings using ambient-
adjusted ratings.
Warmer summer weather can also impact other renewable electric generation. While offshore wind power
may see less seasonal variations, wind power performance for onshore turbines tends to be lowest during
the warmer summer months due to lower average wind speeds, in most U.S. regions. Solar photovoltaic
cells lose efficiency at high air temperatures, and the peak demand for power usually occurs in the late
afternoon and early evening, a few hours after solar power has had its peak generation period in many
regions.
Electricity Price Increases and Customer Demand
Even with increasing amounts of less expensive renewable electricity entering the market, electricity
prices are expected to rise this year largely due to the increasing wholesale prices for natural gas. With the
share of electric power generated from natural gas at about 37% in 2021, and expected to remain at the
same level in 2022, wholesale electric power prices this summer will likely increase. The increase in
natural gas prices has seen some utilities switching to coal, but this is not expected to reverse the decline
in coal use over the longer term. The war in Ukraine is also impacting electric customers, as some
analysts reportedly expect the price of natural gas to remain elevated for a longer period because of the
conflict, and interest in exporting U.S. liquefied natural gas.
As wholesale electricity prices increase, retail rates generally follow. Increased electricity rates are likely
to have a greater effect on lower-income customers who live in older, less energy efficient buildings, and
who spend a higher percentage of their income on cooling. In particular, older lower-income customers
are at increased risk of potential health impacts if they reduce their use of air conditioning to save money.
Potential Climate Change Risks to Power Generation
The U.S. electric power system exists largely in an exposed environment, and is subject to the physical
extremes of climate and weather. The last seven years have been the hottest in recorded history (1880-
2021). Adaptation to historical extremes of weather and climate have been considered in system
hardening and other measures to increase electric system resilience. Some in the electric utility industry
are beginning to realize that a proactive approach is needed to prepare for changing climate conditions.
Going forward, an increasing amount of electric capacity is expected to come from variable renewable
sources that depend on wind and sun. Generation of electric power from these resources largely rely on
weather and the time of day. Variable renewable energy sources now represent much of the uncertainty
regarding power supply planning. A changing climate likely means that the past is not necessarily a
predictor of potential future impacts of weather events on power systems, and electric power system
planners should consider the changing risks as power generation changes from base load to more variable
resources.

Congressional Research Service
3
Author Information

Richard J. Campbell

Specialist in Energy Policy

Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff
to congressional committees and Members of Congress. It operates solely at the behest of and under the direction of
Congress. Information in a CRS Report should not be relied upon for purposes other than public understanding of
information that has been provided by CRS to Members of Congress in connection with CRS’s institutional role.
CRS Reports, as a work of the United States Government, are not subject to copyright protection in the United
States. Any CRS Report may be reproduced and distributed in its entirety without permission from CRS. However,
as a CRS Report may include copyrighted images or material from a third party, you may need to obtain the
permission of the copyright holder if you wish to copy or otherwise use copyrighted material.

IN11964 · VERSION 1 · NEW