The Myth of the 24/7/365 Power Plant

Last week’s polar vortex was so extreme along a vast swath of the Midwest, that bananas could be used as hammers and tossed boiling water froze before hitting the ground. Alongside these homemade lessons in physics, the vortex constituted a big test for our nation’s power sector, and many questioned whether the record-cold temperatures would strain the grid and cause power outages. Fortunately, no major problems occurred.

While no major disruptions occurred, Mother Nature’s brutal blast caused the shutdown of a nuclear reactor in New Jersey; drove many coal plants offline in the Mid-Atlantic and Midwest; and contributed to a fire at a natural gas compression station in Michigan limiting supplies during a time of record demand.

And here’s the irony: it’s the owners of coal and nuclear plants that are arguing for a bailout because of their supposed resilience in the face of extreme weather.

This vortex demonstrates that while no one power source is foolproof, those who manage our grid can balance different resources and events to ensure the light switch or electric starter in your furnace still have a current. It’s also a touchstone of the grid’s reliable and successful transition away from coal towards cleaner resources.

Inspired by the record-breaking vortex, this blog dismantles the myth of the 24/7/365 power plants, an erroneous attribute contrived by coal and nuclear proponents to give undue value to their plants.

Photo by Osman Rana on Unsplash

Coal, nukes and the telegram

The claims of coal and nuclear plant owners touting their reliability got me thinking about an episode of the TV series Madmen. In it, an advertising firm is tasked with creating an ad touting telegrams just as telephone use was booming. In a desperate bid to show the outdated technology as relevant, the team comes up with a slogan: “You can’t frame a phone call.”

Just as advertising executives dug deep to find a killer ad for the vanishing telegram, coal and nuclear plant owners are now touting their own slogan: “24/7/365.” It’s meant to refer to the plants’ supposed unwavering availability to supply power in contrast to supposedly costly and unreliable renewable resources. But here’s the thing: While you can, in fact, frame a telegram, coal and nuclear plants don’t run non-stop.

Without exception, no source of electricity runs full time. Coal, nuclear and gas plants—or conventional resources—periodically experience unexpected outages, and they all need to be turned off periodically for routine maintenance. Their often abrupt failures are sometimes the largest potential failures for which system operators must prepare. In contrast, wind and solar plants have much lower failure rates, and grid planners have deep experience successfully integrating their electricity into the power grid.

Mythical “100 percent reliable plants” are prone to failures

It takes less than an unusual event for conventional resources to shut down. In fact, they periodically go on extended outages, either scheduled or unscheduled. A scheduled shutdown is generally timed to coincide with a plant’s periodic maintenance needs or refueling cycle, while an unscheduled (or forced) shutdown can result from unanticipated equipment and operational failures or environmental factors.

The graph below illustrates the outage rates experienced by the average U.S. coal, gas and nuclear plant. Essentially, the average coal plant is unavailable to supply power about 15 percent of the time, while the average nuclear plant and gas plant are unavailable about 9 percent and 5 percent of the time, respectively.

Estimated percent of time a plant is unavailable. The forced outage rate for coal is 6 to 10 percent, while that of nuclear is 1 to 2 percent.

Data sourced from rough estimates provided by Amory Lovins - "Does “Fuel On Hand” Make Coal and Nuclear Power Plants More Valuable?"

Looking more closely at one specific region, the table below tabulates the probability that conventional generators will not be available due to forced outages in PJM—the nation’s largest grid operator covering the Mid-Atlantic. To address this risk, PJM arranges for additional back-up power that lands on customers’ monthly bill.

Probability that a unit experiences a forced outage - PJM (these numbers do not include planned or maintenance outages)

PJM’s 2017 State of the Market Report

In addition, unexpected outages at conventional plants are sometimes the largest potential failures for which system planners and operators must prepare by making large and costly investments in back-up power.

Both scheduled and forced outages can occur, and have occurred, at awkward times. Here’s a graph showing the capacity unavailable across the middle of the country during the peak hours of electricity demand in each month in 2017.

Capacity Unavailable During Peak Load Hours in 2017

MISO Independent Market Monitor, 2017 State of the Market Report, Analytic Appendix

Notice the grey and purple bars reflecting both planned and forced generator outages. Essentially, many conventional plants were unavailable during peak demand hours in all months.

In addition, generator outages in Mississippi, Arkansas, and Louisiana have undermined the grid operator’s ability to maintain a reliable electricity system. In 2017, higher-than-usual electricity demand in April and September caused by hot temperatures coincided with a large number of planned and forced generator and transmission outages; this created emergency conditions and spikes in electricity prices.

Wind and solar less prone to breakdown

In contrast, unexpected failures are far rarer for wind and solar panel resources. Solar panels have few moving parts and are easily maintained, making their forced outage rate close to zero. Similarly, the forced outage rate of modern wind turbines does not exceed 2 percent. In other words, renewable resources are more technically available compared to conventional resources. Yes, their output varies with the availability of the wind and the sun. However, grid operators and system planners have significantly improved their ability to accurately predict the output from renewable resources and manage its variability.

In addition, more backup power is necessary to protect against conventional plant failures than renewable energy failures. That’s because unlike the gradual changes in renewable output, failures at conventional plants occur instantly and abruptly. In Texas, for example, the cost of integrating large conventional plants onto the grid is more than 17 times larger than the cost of integrating wind energy.

Plus, with the plummeting costs of energy storage and the increased deployment of cheap flexible resources that complement the variability of renewables (like demand response), the complexity of managing the variability of wind and solar is rapidly shrinking.

Entering the Vortex

Coal, nuclear and gas plants have failed just when their power is needed most, during extreme weather events.  

During last weeks’ polar vortex, when blackouts could have been life-threatening, nearly one coal plant in seven was out of action in the Mid-Atlantic region. In fact, natural gas and coal generators accounted for nearly 85 percent of all outages.  Similarly, the cold snap forced the immediate shutdown of a 1,170 MW nuclear reactor in New Jersey. Meanwhile, solar output was strong in the Mid-Atlantic during the morning hours and helped meet high electricity demand in those hours. And while the bitter cold reduced output at a number of wind projects in the Midwest, the grid did not face any reliability issues as a result. In fact, the decline in wind output happened over a relatively long duration of time, not unlike how wind can normally ramp up and down. And the Midwest grid operator is looking for lessons learned to enhance its preparedness for similar extreme events, like the inclusion of extremely low temperature thresholds in its resource forecasting. 

Putting aside last week’s extremely rare arctic blast, wind and solar have overpowered conventional plants in past cold snaps.

The 2014 polar vortex disabled a large number of coal and gas plants in the mid-Atlantic and Northeast. Igniters failed, coal piles and boiler tubes froze, and many plants struggled to run in the extreme cold weather leading to skyrocketing electricity and natural gas prices. In total, gas and coal plants accounted for more than 80 percent of generator forced outages. Meanwhile, wind power and demand response helped carry the grid through both the crisis and the cold winter bracketing it. Importantly, wind power’s consistent output during the 2014 polar vortex helped save customers in the Great Lakes and mid-Atlantic more than $1 billion in two days by supplying cheap electricity. Wind energy provided similar benefits during cold snaps in other regions in early 2014, including California and the Midwest.

And this wasn’t the first time: the February 2011 Southwest cold snap incapacitated dozens of fossil-fueled plants in Texas and affected more than 4 million customers in three states. Meanwhile, wind ­power helped keep the lights on, generating at normal output levels during the worst parts of the emergency.

And during the 2018 January cold snap across the Northeast and Mid-Atlantic—dubbed the Bomb Cyclone—wind production surpassed both average winter and average annual output, generating more than twice its normal level during some of the most challenging periods in the Northeast. Wind output surpassed that of coal on those days.

To sum up: Without exception, all sources of electricity sometimes fail, and grid operators plan for and expect these failures to occur. The “100-percent reliable” conventional plants are mythological and conventional resources should certainly not receive special reliability bonus payments. And with growing grid operator experience, increased deployment of storage and demand response technologies, and continuously improving weather forecasting, integrating wind and solar will continue to become easier.

About the Authors

Rachel Fakhry

Policy Analyst, Climate & Clean Energy Program

Join Us

When you sign up you'll become a member of NRDC's Activist Network. We will keep you informed with the latest alerts and progress reports.