Energy authority clears TEPCO to restart Niigata nuclear plant

2022 U.S. Power Outage Statistics show lower SAIDI as fewer major events hit, with SAIFI trends, electric reliability, outage duration and frequency shaped by hurricanes, winter storms, vegetation, and utility practices across states.

Key Points

They report SAIDI and SAIFI for 2022, showing outage duration, frequency, and impacts of major weather events.

✅ 2022 SAIDI averaged 5.6 hours; SAIFI averaged 1.4 interruptions.

✅ Fewer major events lowered outage duration versus 2021.

✅ Hurricanes and winter storms drove long outages in several states.

In 2022, U.S. electricity consumers on average experienced about 5.5 hours of power disruptions, a decrease from nearly two hours compared to 2021. This information comes from the latest Annual Electric Power Industry Report. The reduction in yearly power interruptions primarily resulted from fewer significant events in 2022 compared to the previous year, and utility disaster planning continues to support grid resilience as severe weather persists.

Since 2013, excluding major events, the annual average duration of power interruptions has consistently hovered around two hours. Factors contributing to major power disruptions include weather-related incidents, vegetation interference near power lines, and specific utility practices, while pandemic-related grid operations influenced workforce planning more than outage frequency. To assess the reliability of U.S. electric utilities, two key indexes are utilized:

• The System Average Interruption Duration Index (SAIDI) calculates the total length (in hours) an average customer endures non-brief power interruptions over a year.
• The System Average Interruption Frequency Index (SAIFI) tracks the number of times interruptions occur.

The influence of major events on electrical reliability is gauged by comparing affected states' SAIDI and SAIFI values against the U.S. average, which was 5.6 hours of outages and 1.4 outages per customer in 2022. The year witnessed 18 weather-related disasters in the U.S., each resulting in over $1 billion in damages, and COVID-19 grid assessments indicated the electricity system was largely safe from pandemic impacts. Noteworthy major events include:

• Hurricane Ian in September 2022, leaving over 2.6 million Floridian customers without electricity, with restoration in some areas taking weeks rather than days.
• Hurricane Nicole in November 2022, causing over 300,000 Florida customers to lose power.
• Winter Storm Elliott in December 2022, affecting over 1.5 million customers in multiple states including Texas where utilities struggled after Hurricane Harvey to restore service, and Florida, and bringing up to four feet of snow in parts of New York.

In 2022, states like Florida, West Virginia, Maine, Vermont, and New Hampshire experienced the most prolonged power interruptions, with New Hampshire averaging 10.3 hours and Florida 19.1 hours, and FPL's Irma storm response illustrates how restoration can take days or weeks in severe cases. Conversely, the District of Columbia, Delaware, Rhode Island, Nebraska, and Iowa had the shortest total interruptions, with the District of Columbia averaging just 34 minutes and Iowa 85 minutes.

The frequency of outages, unlike their duration, is more often linked to non-major events. Across the nation, Alaska recorded the highest number of power disruptions per customer (averaging 3.5), followed by several heavily forested states like Tennessee and Maine. Power outages due to falling tree branches are common, particularly during winter storms that burden tree limbs and power lines, as seen in a North Seattle outage affecting 13,000 customers. The District of Columbia stood out with the shortest and fewest outages per customer.

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Three Mile Island Nuclear Debate spotlights subsidies, carbon pricing, wholesale power markets, grid reliability, and zero-emissions goals as Pennsylvania weighs keeping Exelon's reactor open amid natural gas competition and flat electricity demand.

Key Points

Debate over subsidies, carbon pricing, and grid reliability shaping Three Mile Island's zero-emissions future.

✅ Zero emissions credits vs market integrity

✅ Carbon pricing to value clean baseload power

✅ Closure risks jobs, tax revenue, and reliability

Three Mile Island is at the center of a new conversation about the future of nuclear energy in the United States nearly 40 years after a partial meltdown at the Central Pennsylvania plant sparked a national debate about the safety of nuclear power.

The site is slated to close in just two years, a closure plan Exelon has signaled, unless Pennsylvania or a regional power transmission operator delivers some form of financial relief, says Exelon, the Chicago-based power company that operates the plant.

That has drawn the Keystone State into a growing debate: whether to let struggling nuclear plants shut down if they cannot compete in the regional wholesale markets where energy is bought and sold, or adopt measures to keep them in the business of generating power without greenhouse gas emissions.

""The old compromise — that in order to have a reliable, affordable electric system you had to deal with a significant amount of air pollution — is a compromise our new customers today don't want to hear about.""
-Joseph Dominguez, Exelon executive vice president
Nuclear power plants produce about two-thirds of the country's zero-emissions electricity, a role many view as essential to net-zero emissions goals for the grid.

The debate is playing out as some regions consider putting a price on planet-warming carbon emissions produced by some power generators, which would raise their costs and make nuclear plants like Three Mile Island more viable, and developments such as Europe's nuclear losses highlight broader energy security concerns.

States that allow nuclear facilities to close need to think carefully because once a reactor is powered down, there's no turning back, said Jake Smeltz, chief of staff for Pennsylvania State Sen. Ryan Aument, who chairs the state's Nuclear Energy Caucus.

"If we wave goodbye to a nuclear station, it's a permanent goodbye because we don't mothball them. We decommission them," he told CNBC.

Three Mile Island's closure would eliminate more than 800 megawatts of electricity output. That's roughly 10 percent of Pennsylvania's zero-emissions energy generation, by Exelon's calculation. Replacing that with fossil fuel-fired power would be like putting roughly 10 million cars on the road, it estimates.

A closure would also shed about 650 well-paying jobs, putting the just transition challenge in focus for local workers and communities, tied to about $60 million in wages per year. Dauphin County and Londonderry Township, a rural area on the Susquehanna River where the plant is based, stand to lose $1 million in annual tax revenue that funds schools and municipalities. The 1,000 to 1,500 workers who pack local hotels, stores and restaurants every two years for plant maintenance would stop visiting.

Pennsylvanians and lawmakers must now decide whether these considerations warrant throwing Exelon a lifeline. It's a tough sell in the nation's second-largest natural gas-producing state, which already generates more energy than it uses. And time is running out to reach a short-term solution.

"What's meaningful to us is something where we could see the results before we turn in the keys, and we turn in the keys the third quarter of '19," said Joseph Dominguez, Exelon's executive vice president for governmental and regulatory affairs and public policy.

The end of the nuclear age?

The problem for Three Mile Island is the same one facing many of the nation's 60 nuclear plants: They are too expensive to operate.

Financial pressure on these facilities is mounting as power demand remains stagnant due to improved energy efficiency, prices remain low for natural gas-fired generation and costs continue to fall for wind and solar power.

Three Mile Island is something of a special case: The 1979 incident left only one of its two reactors operational, but it still employs about as many people as a plant with two reactors, making it less efficient. In the last three regional auctions, when power generators lock in buyers for their future energy generation, no one bought power from Three Mile Island.

But even dual-reactor plants are facing existential threats. FirstEnergy Corp's Beaver Valley will sell or close its nuclear plant near the Pennsylvania-Ohio border next year as it exits the competitive power-generation business, and facilities like Ohio's Davis-Besse illustrate what's at stake for the region.

Five nuclear power plants have shuttered across the country since 2013. Another six have plans to shut down, and four of those would close well ahead of schedule. An analysis by energy research firm Bloomberg New Energy Finance found that more than half the nation's nuclear plants are facing some form of financial stress.

Today's regional energy markets, engineered to produce energy at the lowest cost to consumers, do not take into account that nuclear power generates so much zero-emission electricity. But Dominguez, the Exelon vice president, said that's out of step with a world increasingly concerned about climate change.

"What we see is increasingly our customers are interested in getting electricity from zero air pollution sources," Dominguez said. "The old compromise — that in order to have a reliable, affordable electric system you had to deal with a significant amount of air pollution — is a compromise our new customers today don't want to hear about."

Strange bedfellows

Faced with the prospect of nuclear plant closures, Chicago and New York have both allowed nuclear reactors to qualify for subsidies called zero emissions credits. Exelon lobbied for the credits, which will benefit some of its nuclear plants in those states.

Even though the plants produce nuclear waste, some environmental groups like the Natural Resources Defense Council supported these plans. That's because they were part of broader packages that promote wind and solar power, and the credits for nuclear are not open-ended. They essentially provide a bridge that keeps zero-emissions power from nuclear reactors on the grid as renewable energy becomes more viable.

Lawmakers in Pennsylvania, Ohio and Connecticut are currently exploring similar options. Jake Smeltz, chief of staff to state Sen. Aument, said legislation could surface in Pennsylvania as soon as this fall. The challenge is to get people to consider the attributes of the sources of their electricity beyond just cost, according to Smeltz.

"Are the plants worth essentially saving? That's a social choice. Do they provide us with something that has benefits beyond the electrons they make? That's the debate that's been happening in other states, and those states say yes," he said.

Subsidies face opposition from anti-nuclear energy groups like Three Mile Island Alert, as well as natural gas trade groups and power producers who compete against Exelon by operating coal and natural gas plants.

"Where we disagree is to have an out-of-market subsidy for one specific company, for a technology that is now proven and mature in our view, at the expense of consumers and the integrity of competitive markets," NRG Energy Mauricio Gutierrez told analysts during a conference call this month.

Smeltz notes that power producers like NRG would fill in the void left by nuclear plants as they continue to shut down.

"The question that I think folks need to answer is are these programs a bailout or is the opposition to the program a payout? Because at the end of the day someone is going to make money. The question is who and how much?" Smeltz said.

Changing the market

Another critic is PJM Interconnection, the regional transmission organization that operates the grid for 13 states, including Pennsylvania, and Washington, D.C.

The subsidies distort price formation and inject uncertainty into the markets, says Stu Bresler, senior vice president in charge of operations and markets at PJM.

The danger PJM sees is that each new subsidy creates a precedent for government intervention. The uncertainty makes it harder for investors to determine what sort of power generation is a sound investment in the region, Bresler explained. Those investors could simply decide to put their capital to work in other energy markets where the regulatory outlook is more stable, ultimately leading to underinvestment in places where government intervenes, he added.

Three Mile Island nuclear power plant, Londonderry Township, Pennsylvania
PJM believes longer-term, regional approaches are more appropriate. It has produced research that outlines how coal plants and nuclear energy, which provide the type of stable energy that is still necessary for reliable power supply, could play a larger role in setting prices. It is also preparing to release a report on how to put a price on carbon emissions in all or parts of the regional grid.

"If carbon emissions are the concern and that is the public policy issue with which policymakers are concerned, the simple be-all answer from a market perspective is putting a price on carbon," Bresler said.

Three Mile Island could be viable if natural gas prices rose from below $3 per million British thermal units to about $5 per mmBtu and if a "reasonable" price were applied to carbon, according to Exelon's Dominguez. He is encouraged by the fact that conversations around new pricing models and carbon pricing are gaining traction.

"The great part about this is everybody understands we have a major problem. We're losing some of the lowest-cost, cleanest and most reliable resources in America," Dominguez said.

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California Utility Spending Bill scrutinizes how ratepayer funds are used by utilities, targeting lobbying, advertising, wildfire prevention cost pass-throughs, and CPUC oversight to curb high electricity bills and increase accountability and transparency statewide.

Key Points

Legislation restricting utilities from using ratepayer money for lobbying and ads, with stronger CPUC oversight.

✅ Bans ratepayer-funded lobbying and political advertising

✅ Expands prohibited utility communications and influence spending

✅ Aims to curb bills, boost transparency, and CPUC accountability

California's legislators are about to vote on a bill that would impose stricter regulations on how utility companies spend the money they collect from ratepayers. This legislation directly responds to the growing discontent among Californians who are already grappling with high electricity bills, as Californians ask why electricity prices are soaring amid wildfire prevention efforts.

Consumer rights groups have been vehemently critical of how utilities have been allocating customer funds, amid growing calls for regulatory action from state officials. They allege that a substantial portion of this money is being funnelled into lobbying efforts and advertising campaigns that yield no direct benefits for the customers themselves.

The proposed bill would significantly broaden the definition of what constitutes prohibited advertising and political influence activities on the part of utility companies, separate from income-based fixed electricity charges proposals that affect rate design. This would effectively restrict the ways in which utilities can utilize customer funds for such purposes.

While consumer advocacy groups have favored the legislation, it has drawn opposition from utility companies and some labor unions, as lawmakers weigh overturning income-based utility charges in parallel debates. Opponents contend that it would hinder utilities' ability to communicate effectively with their customers and advocate for their interests. Additionally, they express concerns that the bill could result in job losses within the utility sector.

The vote on the bill is expected to take place on Monday. The outcome of the vote is uncertain, but it is sure to be a closely watched development for Californians struggling with the burden of high electricity bills, with many wondering about major changes to their electric bills in the near term.

California's Electricity Rates: A Burden for Residents

A recent report by the California Public Utilities Commission (CPUC) revealed that the average Californian household spends a significantly higher amount on electricity compared to the national average. This disparity in electricity rates can be attributed to a number of factors, including the financial costs associated with wildfire prevention measures, investments in renewable energy infrastructure, and maintenance of aging electrical grids, even as the state considers revamping electricity rates to clean the grid.

Examples of Utility Company Spending that Raise Concerns

Consumer rights groups have specifically highlighted instances where utility companies have used customer money to fund lavish executive compensation packages, sponsor professional sports teams, and finance political campaigns. They argue that these expenditures do not provide any tangible benefits to ratepayers and should not be funded through customer bills.

The Need for Accountability and Prioritization

Proponents of the bill believe that the legislation is necessary to ensure that utility companies are held accountable for how they spend customer funds. They believe that the stricter regulations would compel utilities to prioritize investments that directly improve the quality and reliability of electricity services for Californians, alongside discussions of income-based flat-fee utility bills that could reshape rate structures.

The impending vote on the bill underscores the ongoing tension between the need for reliable electricity services and the desire to keep utility rates affordable for Californians. The outcome of the vote is likely to have a significant impact on how utility companies operate in the state and how much Californians pay for their electricity.

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Clean Power Plan Rollback signals EPA's shift to inside-the-fence efficiency at coal plants, emphasizing heat-rate improvements over sector-wide decarbonization, renewables, natural gas switching, demand-side efficiency, and carbon capture under Clean Air Act constraints.

Key Points

A policy shift by the EPA to replace broad emissions rules with plant-level efficiency standards, limiting CO2 cuts.

✅ Inside-the-fence heat-rate improvements at coal units

✅ Potential CO2 cuts limited to about 6% per plant

✅ Alternatives: fuel switching, renewables, carbon capture

President Barack Obama’s signature plan to reduce carbon dioxide emissions from electrical generation took years to develop and touched every aspect of power production and use, from smokestacks to home insulation.

The Trump administration is moving to scrap that plan and has signaled that any alternative it might adopt would take a much less expansive approach, possibly just telling utilities to operate their plants more efficiently.

That’s a strategy environmentalists say is almost certain to fall short of what’s needed.

The Trump administration is making "a wholesale retreat from EPA’s legal, scientific and moral obligation to address the threats of climate change," said former Environmental Protection Agency head Gina McCarthy, the architect of Obama’s Clean Power Plan.

President Donald Trump promised to rip up the initiative, echoing an end to the 'war on coal' message from his campaign, which mandated that states change their overall power mix, displacing coal-fired electricity with that from wind, solar and natural gas. The EPA is about to make it official, arguing the prior administration violated the Clean Air Act by requiring those broad changes to the electricity sector, according to a draft obtained by Bloomberg.

Possible Replacements

Later, the agency will also ask the public to weigh in on possible replacements. The administration will ask whether the EPA can or should develop a replacement rule -- and, if so, what actions can be mandated at individual power plants, though some policymakers favor a clean electricity standard to drive broader decarbonization.

Follow the Trump Administration’s Every Move

Such changes -- such as adding automation or replacing worn turbine seals -- would yield at most a 6 percent gain in efficiency, along with a corresponding fall in greenhouse gas emissions, according to earlier modeling by the Environmental Protection Agency and other analysts. That compares to the 32 percent drop in emissions by 2030 under Obama’s Clean Power Plan.

"In these existing plants, there’s only so many places to look for savings," said John Larsen, a director of the Rhodium Group, a research firm. "There’s only so many opportunities within a big spinning machine like that."

EPA Administrator Scott Pruitt outlined such an "inside-the-fence-line" approach in 2014, later embodied in the Affordable Clean Energy rule that industry groups backed, when he served as Oklahoma’s attorney general. Under his blueprint, states would set emissions standards after a detailed unit-by-unit analysis, looking at what reductions are possible given "the engineering limits of each facility."

The EPA has not decided whether it will promulgate a new rule at all, though it has also proposed new pollution limits for coal and gas plants in separate actions. In a forthcoming advanced notice of proposed rulemaking, the EPA will ask "what inside-the-fence-line options are legal, feasible and appropriate," according to a document obtained by Bloomberg.

Increased efficiency at a coal plant -- known as heat-rate improvement -- translates into fewer carbon-dioxide emissions per unit of electric power generated.

Under Obama, the EPA envisioned utilities would make some straightforward efficiency improvements at coal-fired power plants as the first step to comply with the Clean Power Plan. But that was expected to coincide with bigger, broader changes -- such as using more cleaner-burning natural gas, adding more renewable power projects and simply encouraging customers to do a better job turning down their thermostats and turning off their lights.

Obama’s EPA didn’t ask utilities to wring every ounce of efficiency they could out of coal-fired power plants because they saw the other options as cheaper. A plant-specific approach "would be grossly insufficient to address the public health and environmental impacts from CO2 emissions," Obama’s EPA said.

That approach might yield modest emissions reductions and, in a perverse twist, might event have the opposite effect. If utilities make coal plants more efficient -- thereby driving down operating costs -- they also make them more competitive with natural gas and renewables, "so they might run more and pollute more," said Conrad Schneider, advocacy director for the Clean Air Task Force.  

In a competitive market, any improvement in emissions produced for each unit of energy could be overwhelmed by an increase in electrical output, and debates over changes to electricity pricing under Trump and Perry added further uncertainty.

"A very minor heat rate improvement program would very likely result in increased emissions," Schneider said. "It might be worse than nothing."

Power companies want to get as much electricity as possible from every pound of coal, so they already have an incentive to keep efficiency high, said Jeff Holmstead, a former assistant EPA administrator now at Bracewell LLP. But an EPA regulation known as “new source review” has discouraged some from making those changes, for fear of triggering other pollution-control requirements, he said.

"If EPA’s replacement rule allows companies to improve efficiency without triggering new source review, it would make a real difference in terms of reducing carbon-dioxide emissions," Holmstead said.

Modest Impact

A plant-specific approach doesn’t have to mean modest impact.

"If you’re thinking about what can be done at the power plants by themselves, you don’t stop at efficiency tune-ups," said David Doniger, director of the Natural Resources Defense Council’s climate and clean air program. "You look at things like switching to natural gas or installing carbon capture and storage."

Requirements that facilities use carbon capture technology or swap in natural gas for coal could actually come close to hitting the same goals as in Obama’s Clean Power Plan -- if not go even further, Schneider said. They just would cost more.

The benefit of the Clean Power Plan "is that it enabled states to create programs and enabled companies to find a reduction strategy that was the most efficient and made the most sense for their own content," said Kathryn Zyla, deputy director of the Georgetown Climate Center. "And that flexibility was really important for the states and companies."

Some utilities, including Houston-based Calpine Corp., PG&E Corp. and Dominion Resources Inc., backed the Obama-era approach. And they are still pushing the Trump administration to be creative now.

"The Clean Power Plan achieved a thoughtful, balanced approach that gave companies and states considerable flexibility on how best to pursue that goal," said Melissa Lavinson, vice president of federal affairs and policy for PG&E’s Pacific Gas and Electric utility. “We look forward to working with the administration to devise an alternative plan for decarbonizing the U.S. economy."

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KHNP Shortlisted for Belene Nuclear Power Plant, named by the Bulgarian Energy Ministry alongside Rosatom and CNNC; highlights APR1400 reactor expertise, EPC credentials, and expansion into the European nuclear energy market.

Key Points

KHNP is a strategic investor candidate for Bulgaria's Belene NPP, leveraging APR1400 and European market entry.

✅ Selected with Rosatom and CNNC by Bulgarian Energy Ministry

✅ Builds on APR1400 reactor design and EPC track record

✅ Positions KHNP for EU nuclear projects and O&M services

Korea Hydro & Nuclear Power (KHNP) has been selected as one of the three strategic investor candidates for a Bulgarian nuclear power plant project amid global nuclear project milestones worldwide.

The Bulgarian Energy Ministry selected KHNP of Korea, RosAtom of Russia and CNNC of China as strategic investor candidates for the construction of the Belene Nuclear Power Plant, KHNP said on Dec. 20. The Belene Nuclear Power Plant is the second nuclear power plant that Bulgaria plans to build following the 2,000-megawatt Kozloduy Nuclear Power Plant built in 1991 during the Soviet Union era. The project budget is estimated at 10 billion euros.

By being included in the shortlist for the Bulgarian project, KHNP has boosted the possibility of making a foray into the European nuclear power plant market, as India takes steps to get nuclear back on track worldwide. KHNP began to export nuclear power plants in 2009 by winning the UAE Barakah Nuclear Power Plant Project, with Barakah Unit 1 reaching 100% power as it moves toward commercial operations. The UAE plant will be based on the APR1400, a next-generation Korean nuclear reactor that is used in Shin Kori Units 3 and 4 in Korea.

The ARP1400 is a Korean nuclear reactor developed by KHNP with investment of about 230 billion won for 10 years from 1992. The nuclear reactor became the first non-U.S. type reactor to receive a design certificate (DC) from the U.S. Nuclear Regulatory Commission (NRC), as China's nuclear energy program continues on a steady development track globally. By receiving the DC, its safety was internationally recognized. In June, the company also won the maintenance project for the Barakah Nuclear Power Plant, completing the entire cycle from the construction of the nuclear power plant to its design, operation and maintenance. However, U.S. and U.K. companies took part of the maintenance project for the nuclear power plant.

In July, KHNP officials visited Turkey and contacted local energy officials to prepare for nuclear power plant projects to be launched in that country, as Bangladesh develops nuclear power with IAEA assistance in the region. Earlier in May, the company also submitted a proposal to participate in the construction of a new nuclear power plant in Kazakhstan, while Kenya moves forward with plans for a $5 billion plant.

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IESO Fictitious Demand Error inflated HOEP in the Ontario electricity market, after embedded generation was mis-modeled; the OEB says double-counted load lifted wholesale prices and shifted costs via the Global Adjustment.

Key Points

An IESO modeling flaw that double-counted load, inflating HOEP and charges in Ontario's wholesale market.

✅ Double-counted unmetered load from embedded generation

✅ Inflated HOEP; shifted costs via Global Adjustment

✅ OEB flagged transparency; exporters paid more

For almost a year, the operator of Ontario’s electricity system erroneously counted enough phantom demand to power a small city, causing prices to spike and hundreds of millions of dollars in extra charges to consumers, according to the provincial energy regulator.

The Independent Electricity System Operator (IESO) also failed to tell anyone about the error once it noticed and fixed it.

The error likely added between $450 million and $560 million to hourly rates and other charges before it was fixed in April 2017, according to a report released this month by the Ontario Energy Board’s Market Surveillance Panel.

It did this by adding as much as 220 MW of “fictitious demand” to the market starting in May 2016, when the IESO started paying consumers who reduced their demand for power during peak periods. This involved the integration of small-scale embedded generation (largely made up of solar) into its wholesale model for the first time.

The mistake assumed maximum consumption at such sites without meters, and double-counted that consumption.

The OEB said the mistake particularly hurt exporters and some end-users, who did not benefit from a related reduction of a global adjustment rate applicable to other customers.

“The most direct impact of the increase in HOEP (Hourly Ontario Energy Price) was felt by Ontario consumers and exporters of electricity, who paid an artificially high HOEP, to the benefit of generators and importers,” the OEB said.

The mix-up did not result in an equivalent increase in total system costs, because changes to the HOEP are offset by inverse changes to a electricity cost allocation mechanism such as the Global Adjustment rate, the OEB noted.

A chart from the OEB's report shows the time of day when fictitious demand was added to the system, and its influence on hourly rates.

Peak time spikes
The OEB said that the fictitious demand “regularly inflated” the hourly price of energy and other costs calculated as a direct function of it.

For almost a year, Ontario's electricity system operator @IESO_Tweets erroneously counted enough phantom demand to power a small city, causing price spikes and hundreds of millions in charges to consumers, @OntEnergyBoard says. @5thEstate reports.

It estimated the average increase to the HOEP was as much as $4.50/MWh, but that price spikes, compounded by scheduled OEB rate changes, would have been much higher during busier times, such as the mid-morning and early evening.

“In times of tight supply, the addition of fictitious demand often had a dramatic inflationary impact on the HOEP,” the report said.

That meant on one summer evening in 2016 the hourly rate jumped to $1,619/MWh, it said, which was the fourth highest in the history of the Ontario wholesale electricity market.

“Additional demand is met by scheduling increasingly expensive supply, thus increasing the market price. In instances where supply is tight and the supply stack is steep, small increases in demand can cause significant increases in the market price.

The OEB questioned why, as of September this year, the IESO had failed to notify its customers or the broader public, amid a broader auditor-regulator dispute that drew political attention, about the mistake and its effect on prices.

“It's time for greater transparency on where electricity costs are really coming from,” said Sarah Buchanan, clean energy program manager at Environmental Defence.

“Ontario will be making big decisions in the coming years about whether to keep our electricity grid clean, or burn more fossil fuels to keep the lights on,” she added. “These decisions need to be informed by the best possible evidence, and that can't happen if critical information is hidden.”

In a response to the OEB report on Monday, the IESO said its own initial analysis found that the error likely pushed wholesale electricity payments up by $225 million. That calculation assumed that the higher prices would have changed consumer behaviour, while upcoming electricity auctions were cited as a way to lower costs, it said.

In response to questions, a spokesperson said residential and small commercial consumers would have saved $11 million in electricity costs over the 11-month period, even as a typical bill increase loomed province-wide, while larger consumers would have paid an extra $14 million.

That is because residential and small commercial customers pay some costs via time-of-use rates, including a temporary recovery rate framework, the IESO said, while larger customers pay them in a way that reflects their share of overall electricity use during the five highest demand hours of the year.

The IESO said it could not compensate those that had paid too much, given the complexity of the system, and that the modelling error did not have a significant impact on ratepayers.

While acknowledging the effects of the mistake would vary among its customers, the IESO said the net market impact was less than $10 million, amid ongoing legislation to lower electricity rates in Ontario.

It said it would improve testing of its processes prior to deployment and agreed to publicly disclose errors that significantly affect the wholesale market in the future.

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