Renewables became the second-most prevalent U.S. electricity source in 2020


2020 us renewables graph

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2020 U.S. Renewable Electricity Generation set a record as wind, solar, hydro, biomass, and geothermal produced 834 billion kWh, surpassing coal and nuclear, second only to natural gas in nationwide power output.

 

Key Points

The record year when renewables made 834 billion kWh, topping coal and nuclear in U.S. electricity.

✅ Renewables supplied 21% of U.S. electricity in 2020

✅ Coal output fell 20% y/y; nuclear slipped 2% on retirements

✅ EIA forecasts renewables rise in 2021-2022; coal rebounds

 

In 2020, renewable energy sources (including wind, hydroelectric, solar, biomass, and geothermal energy) generated a record 834 billion kilowatthours (kWh) of electricity, or about 21% of all the electricity generated in the United States. Only natural gas (1,617 billion kWh) produced more electricity than renewables in the United States in 2020. Renewables surpassed both nuclear (790 billion kWh) and coal (774 billion kWh) for the first time on record. This outcome in 2020 was due mostly to significantly less coal use in U.S. electricity generation and steadily increased use of wind and solar generation over time, amid declining consumption trends nationwide.

In 2020, U.S. electricity generation from coal in all sectors declined 20% from 2019, while renewables, including small-scale solar, increased 9%. Wind, currently the most prevalent source of renewable electricity in the United States, grew 14% in 2020 from 2019, and the EIA expects solar and wind to be larger sources in summer 2022, reflecting continued growth. Utility-scale solar generation (from projects greater than 1 megawatt) increased 26%, and small-scale solar, such as grid-connected rooftop solar panels, increased 19%, while early 2021 January power generation jumped year over year.

Coal-fired electricity generation in the United States peaked at 2,016 billion kWh in 2007 and much of that capacity has been replaced by or converted to natural gas-fired generation since then. Coal was the largest source of electricity in the United States until 2016, and 2020 was the first year that more electricity was generated by renewables and by nuclear power than by coal (according to our data series that dates back to 1949). Nuclear electric power declined 2% from 2019 to 2020 because several nuclear power plants retired and other nuclear plants experienced slightly more maintenance-related outages.

We expect coal-fired generation to increase in the United States during 2021 as natural gas prices continue to rise and as coal becomes more economically competitive. Based on forecasts in our Short-Term Energy Outlook (STEO), we expect coal-fired electricity generation in all sectors in 2021 to increase 18% from 2020 levels before falling 2% in 2022. We expect U.S. renewable generation across all sectors to increase 7% in 2021 and 10% in 2022, and in 2021, non-fossil fuel sources accounted for about 40% of U.S. electricity. As a result, we forecast coal will be the second-most prevalent electricity source in 2021, and renewables will be the second-most prevalent source in 2022. We expect nuclear electric power to decline 2% in 2021 and 3% in 2022 as operators retire several generators.

 

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The underwater 'kites' generating electricity as they move

Faroe Islands Tidal Kites harness predictable ocean energy with underwater turbines by Minesto, flying figure-eight paths in fjords to amplify tidal power and deliver renewable electricity to SEV's grid near Vestmanna at megawatt scale.

 

Key Points

Subsea turbines that fly figure-eight paths to harvest tidal currents, delivering reliable renewable power to the grid.

✅ Figure-eight control amplifies speed vs. ambient current

✅ Predictable baseload complementing wind and hydro

✅ 1.2 MW Dragon-class units planned for Faroese fjords

 

Known as "sea dragons" or "tidal kites", they look like aircraft, but these are in fact high-tech tidal turbines, part of broader ocean and river power efforts generating electricity from the power of the ocean.

The two kites - with a five-metre (16ft) wingspan - move underwater in a figure-of-eight pattern, absorbing energy from the running tide. They are tethered to the fjord seabed by 40-metre metal cables.

Their movement is generated by the lift exerted by the water flow - just as a plane flies by the force of air flowing over its wings.

Other forms of tidal power use technology similar to terrestrial wind turbines, and emerging kite-based wind power shows the concept's versatility, but the kites are something different.

The moving "flight path" allows the kite to sweep a larger area at a speed several times greater than that of the underwater current. This, in turn, enables the machines to amplify the amount of energy generated by the water alone.

An on-board computer steers the kite into the prevailing current, then idles it at slack tide, maintaining a constant depth in the water column. If there were several kites working at once, the machines would be spaced far enough apart to avoid collisions.

The electricity is sent via the tethering cables to others on the seabed, and then to an onshore control station near the coastal town of Vestmanna.

The technology has been developed by Swedish engineering firm Minesto, founded back in 2007 as a spin-off from the country's plane manufacturer, Saab.

The two kites in the Faroe Islands have been contributing energy to Faroe's electricity company SEV, and the islands' national grid, on an experimental basis over the past year.

Each kite can produce enough electricity to power approximately 50 to 70 homes.

But according to Minesto chief executive, Martin Edlund, larger-scale beasts will enter the fjord in 2022.

"The new kites will have a 12-metre wingspan, and can each generate 1.2 megawatts of power [a megawatt is 1,000 kilowatts]," he says. "We believe an array of these Dragon-class kites will produce enough electricity to power half of the households in the Faroes."

The 17 inhabited Faroe islands are an autonomous territory of Denmark. Located halfway between Shetland and Iceland, in a region where U.K. wind lessons resonate, they are home to just over 50,000 people.

Known for their high winds, persistent rainfall and rough seas, the islands have never been an easy place to live. Fishing is the primary industry, accounting for more than 90% of all exports.

The hope for the underwater kites is that they will help the Faroe Islands achieve its target of net-zero emission energy generation by 2030, with advances in wave energy complementing tidal resources along the way.

While hydro-electric power currently contributes around 40% of the islands' energy needs, wind power contributes around 12% and fossil fuels - in the form of diesel imported by sea - still account for almost half.

Mr Edlund says that the kites will be a particularly useful back-up when the weather is calm. "We had an unusual summer in 2021 in Faroes, with about two months with virtually no wind," he says.

"In an island location there is no possibility of bringing in power connections from another country, and tidal energy for remote communities can help, when supplies run low. The tidal motion is almost perpetual, and we see it as a crucial addition to the net zero goals of the next decade."

Minesto has also been testing its kites in Northern Ireland and Wales, where offshore wind in the UK is powering rapid growth, and it plans to install a farm off the coast of Anglesey, plus projects in Taiwan and Florida.

The Faroe Islands' drive towards more environmental sustainability extends to its wider business community, with surging offshore wind investment providing global momentum. The locals have formed a new umbrella organisation - Burðardygt Vinnulív (Faroese Business Sustainability Initiative).

It currently has 12 high-profile members - key players in local business sectors such as hotels, energy, salmon farming, banking and shipping.

The initiative's chief executive - Ana Holden-Peters - believes the strong tradition of working collaboratively in the islands has spurred on the process. "These businesses have committed to sustainability goals which will be independently assessed," she says.

"Our members are asking how they can make a positive contribution to the national effort. When people here take on a new idea, the small scale of our society means it can progress very rapidly."

One of the islands' main salmon exporters - Hiddenfjord - is also doing its bit, by ceasing the air freighting of its fresh fish. Thought to be a global first for the Atlantic salmon industry, it is now exporting solely via sea cargo instead.

According to the firm's managing director Atli Gregersen this will reduce its transportation CO2 emissions by more than 90%. However it is a bold move commercially as it means that its salmon now takes much longer to get to key markets.

For example, using air freight, it could get its salmon to New York City within two days, but it now takes more than a week by sea.

What has made this possible is better chilling technology that keeps the fresh fish constantly very cold, but without the damaging impact of deep freezing it. So the fish is kept at -3C, rather than the -18C or below of typical commercial frozen food transportation.

"It's taken years to perfect a system that maintains premium quality salmon transported for sea freight rather than plane," says Mr Gregersen. "And that includes stress-free harvesting, as well as an unbroken cold-chain that is closely monitored for longer shelf life.

"We hope, having shown it can be done, that other producers will follow our lead - and accept the idea that salmon were never meant to fly."

Back in the Faroe Island's fjords, a firm called Ocean Rainforest is farming seaweed.

The crop is already used for human food, added to cosmetics, and vitamin supplements, but the firm's managing director Olavur Gregersen is especially keen on the potential of fermented seaweed being used as an additive to cattle feed.

He points to research which appears to show that if cows are given seaweed to eat it reduces the amount of methane gas that they exhale.

"A single cow will burp between 200 and 500 litres of methane every day, as it digests," says Mr Gregersen. "For a dairy cow that's three tonnes per animal per year.

"But we have scientific evidence to show that the antioxidants and tannins in seaweed can significantly reduce the development of methane in the animal's stomach. A seaweed farm covering just 10% of the largest planned North Sea wind farm could reduce the methane emissions from Danish dairy cattle by 50%."

The technology that Ocean Rainforest uses to farm its four different species of seaweed is relatively simple. Tiny algal seedlings are affixed to a rope which dangles in the water, and they grow rapidly. The line is lifted using a winch and the seaweed strands simply cut off with a knife. The line goes back into the water, and the seaweed starts growing again.

Currently, Ocean Rainforest is harvesting around 200 tonnes of seaweed per annum in the Faroe Islands, but plans to scale this up to 8,000 tonnes by 2025. Production may also be expanded to other areas in Europe and North America.

 

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US Moving Towards 30% Electricity From Wind & Solar

US Wind and Solar Outlook 2026 projects cheap renewables displacing coal and gas, with utility-scale additions, rooftop solar growth, improved grid reliability, and EV V2G integration accelerating decarbonization across the electricity market.

 

Key Points

An analysis forecasting wind and solar growth, displacing coal and gas as utility-scale and rooftop solar expand.

✅ Utility-scale solar installs avg 21 GW/yr through 2026.

✅ 37.7 GW wind in pipeline; 127.8 GW already online.

✅ Small-scale solar could near 100 TWh in 2026.

 

A recent report from the Institute for Energy Economics and Financial Analysis (IEEFA) predicts that cheap renewables in the form of wind and solar will push coal and gas out of the energy market space. Already at 9% of US generation, the report predicts that wind and solar will supply almost 30% of US electricity demand by 2026, consistent with renewables nearing one-fourth of U.S. generation projections for the near term.

“The Solar Energy Industries Association now expects utility-scale installations to average more than 21,000MW a year through 2026, following a year when U.S. solar generation rose 25% and with a peak of 25,000MW in 2023,” IEEFA writes. “Continued growth is also expected in U.S. wind generation, mirroring global trends where China's solar PV expansion outpaced all other fuels in 2016, with 37.7GW of new capacity already under construction or in advanced development, which would be added to 127.8GW in existing installed capacity.”

Meanwhile, with wind and solar growth booming, fossil fuels are declining, as renewables surpassed coal in 2022 nationwide. “Coal and natural gas are now locked into an essentially zero-sum game where increases in one fuel’s generation comes at the expense of the other. Together, they are not gaining market share, rather they are trading it back and forth, and the rapid growth in renewable generation will cut even deeper into the market share of both.”

And what of rooftop solar? Some states in Australia now have periods where the entire state grid is powered just by solar on the roofs of private citizens. As this revolution progresses in the USA, especially if a tenfold national solar push moves forward, what impact will it make on fossil fuel generators — which are expensive to build, expensive to maintain, expensive to fuel, and rely on an expensive distribution network.

“EIA estimates that this ‘small-scale solar’ produced 41.7 million MWh of power in 2020, when solar accounted for about 3% of U.S. electricity, a 19 percent increase from 2019. This growth will likely continue in the years ahead as costs continue to fall and concerns about grid reliability rise. Assuming a conservative 15 percent annual increase in small-scale solar going forward would push the sector’s generation to almost 100 million MWh in 2026.”

The Joker in the story might be the impact from electric vehicle adoption. Sales are set to surge and there’s more and more interest in V2G technology, even as wind and solar could provide 50% by 2050 in broader forecasts.

 

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Toronto to start trial run of 'driverless' electric vehicle shuttles

Toronto Olli 2.0 Self-Driving Shuttle connects West Rouge to Rouge Hill GO with autonomous micro-transit. Electric shuttle pilot by Local Motors and Pacific Western Transportation, funded by Transport Canada, features accessibility, TTC and Metrolinx support.

 

Key Points

An autonomous micro-transit pilot linking West Rouge to Rouge Hill GO, with accessibility and onboard staff.

✅ Last-mile link: West Rouge to Rouge Hill GO

✅ Accessible: ramp, wheelchair securement, A/V announcements

✅ Operated with attendants; funded by Transport Canada

 

The city of Toronto, which recently opened an EV education centre to support adoption, has approved the use of a small, self-driving electric shuttle vehicle that will connect its West Rouge neighbourhood to the Rouge Hill GO station, a short span of a few kilometres.

It’s called the Olli 2.0, and it’s a micro-shuttle with service provided by Local Motors, in partnership with Pacific Western Transportation, as the province makes it easier to build EV charging stations to support growing demand.

The vehicle is designed to hold only eight people, and has an accessibility ramp, a wheelchair securement system, audio and visual announcements, and other features for providing rider information, aligning with transit safety policies such as the TTC’s winter lithium-ion device restrictions across the system.

“We are continuing to move our city forward on many fronts including micro-transit as we manage the effects of COVID-19,” said Mayor John Tory. “This innovative project will provide valuable insight, while embracing innovation that could help us build a better, more sustainable and equitable transportation network.”

At the provincial level, the public EV charging network has faced delays, underscoring infrastructure challenges.


Although the vehicle is “self-driving,” it will still require two people onboard for every trip during the six- to 12-month trial; those people will be a certified operator from Pacific Western Transportation, and either a TTC ambassador from an agency introducing battery electric buses across its fleet, or a Metrolinx customer service ambassador.

Funding for the program comes from Transport Canada, as part of a ten-year pilot program to test automated vehicles on Ontario’s roads that was approved in 2016, and it complements lessons from the TTC’s largest battery-electric bus fleet as well as emerging vehicle-to-grid programs that engage EV owners.

 

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EV charging to solar panels: How connected tech is changing the homes we live in

Connected Home Energy Technologies integrate solar panels, smart meters, EV charging, battery storage, and IoT energy management to cut costs, optimize demand response, and monitor usage in real time for safer, lower-carbon homes.

 

Key Points

Devices and systems managing home energy: solar PV, smart meters, EV chargers, and storage to cut costs and emissions.

✅ Real-time visibility via apps, smart meters, and IoT sensors

✅ Integrates solar PV, batteries, and EV charging with the grid

✅ Enables demand response, lower bills, and lower carbon

 

Driven by advances in tech and the advent of high-speed internet connections, many of us now have easy access to a raft of information about the buildings we live in.

Thanks to the proliferation of hardware and software within the home, this trend shows no sign of letting up and comes in many different forms, from indoor air quality monitors to “smart” doorbells which provide us with visual, real-time notifications when someone is attempting to access our property.

Residential renewable electricity generation is also starting to gain traction, with a growing number of people installing solar panels in the hope of reducing bills and their environmental footprint.

In the U.S. alone, the residential solar market installed 738 megawatts of capacity in the third quarter of 2020, a 14% jump compared to the second quarter, according to a recent report from the Solar Energy Industries Association and Wood Mackenzie.

Earlier this month, California-headquartered SunPower — which specializes in the design, production and delivery of solar panels and systems — announced it was rolling out an app which will enable homeowners to assess and manage their energy generation, usage and battery storage settings with their mobile, as California looks to EVs for grid stability amid broader electrification.

The service will be available to customers using its SunPower Eqiunox system and represents yet another instance of how connected technologies can provide us with valuable information about how buildings operate.

Similar offerings in this increasingly crowded marketplace include so-called “smart” meters, which allow consumers to see how much energy they are using and money they are spending in real time.

Elsewhere products such as Hive, from Centrica, enable users to install a range of connected kit — from plugs and lighting to thermostats and indoor cameras — that can be controlled via an app on their cellphone and, in some cases, their voice. 

Connected car charging
Solar panels represent one way that sustainable tech can be integrated into homes. Other examples include the installation of charging points for electric vehicles, as EV growth challenges state grids in many markets.

With governments around the world looking to phase-out the sale of diesel and gasoline vehicles and encourage consumers to buy electric, and Model 3's utility impact underscoring likely shifts in demand, residential charging systems could become an integral part of the built environment in the years ahead.

Firms offering home-based, connected, charging include Pod Point and BP Pulse. Both of these services include apps which provide data such as how much energy has been used, the cost of charging and charge history.  

Another firm, Wallbox, recently announced it was launching its first electric vehicle charger for North American homes.

The company, which is based in Spain, said the system was compatible with all types of electric vehicles, would allow customers to schedule charges, and could be voice-controlled through Google Assistant and Amazon Alexa, while mobile energy storage promises added flexibility for strained grids.

Away from the private sector, governments are also making efforts to encourage the development of home charging infrastructure.

Over the weekend, U.K. authorities said the Electric Vehicle Homecharge Scheme — which gives drivers as much as £350 (around $487) toward a charging system — would be extended and expanded, targeting those who live in leasehold and rented properties, even as UK grid capacity for EVs remains under scrutiny.

Mike Hawes, chief executive of the Society of Motor Manufacturers and Traders, described the government’s announcement as “welcome and a step in the right direction.”

“As we race towards the phase out of sales of new petrol and diesel cars and vans by 2030, we need to accelerate the expansion of the electric vehicle charging network, and proper grid management can ensure EVs are accommodated at scale,” he added.

“An electric vehicle revolution will need the home and workplace installations this announcement will encourage, but also a massive increase in on-street public charging and rapid charge points on our strategic road network.”

Change afoot, but challenges ahead
As attempts to decarbonize buildings and society ramp up, the way our homes look and function could be on the cusp of quite a big shift.

“Grid-connected home generation technologies such as solar electric panels will be important in the shift to a 100% renewable electricity grid, but decarbonising the electricity supply is only one part of the transition,” Peter Tyldesley, chief executive of the Centre for Alternative Technology, told CNBC via email.

With reference to Britain, Tyldesley went on to explain how his organization envisaged “just under 10% of electricity in a future zero carbon society coming from solar PV, utilising 15-20% of … U.K. roof area.” This, he said, compared to over 75% of electricity coming from wind power. 

Heating, Tyldesley went on to state, represented “the bigger challenge.”

“To decarbonise the U.K.’s housing stock at the scale and speed needed to get to zero carbon, we’ll need to refurbish possibly a million houses every year for the next few decades to improve their insulation and airtightness and to install heat pumps or other non-fossil fuel heating,” he said.

“To do this, we urgently need a co-ordinated national programme with a commitment to multi-year government investment,” he added.

On the subject of buildings becoming increasingly connected, providing us with a huge amount of data about how they function, Tyldesley sought to highlight some of the opportunities this could create. 

“Studies of the roll out of smart metering technology have shown that consumers use less energy when they are able to monitor their consumption in real time, so this kind of technology can be a useful part of behaviour change programmes when combined with other forms of support for home efficiency improvements,” he said.

“The roll out of smart appliances can go one step further — responding to signals from the grid and, through vehicle-to-grid power, helping to shift consumption away from peak times towards periods when more renewable energy is available,” he added.

 

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The N.L. government is pushing the electric car but Labrador's infrastructure is lagging behind

Labrador EV Charging Infrastructure faces gaps, with few fast chargers; Level 2 dominates, fueling range anxiety for Tesla and Chevrolet Bolt drivers, despite rebates and Newfoundland's network linking St. John's to Port aux Basques.

 

Key Points

It refers to the current and planned network of Level 2 and Level 3 charging sites across Labrador.

✅ 2 public Level 2 chargers: Happy Valley-Goose Bay and Churchill Falls

✅ Phase 2: 3 fast chargers planned for HV-GB, Churchill Falls, Labrador City

✅ $2,500 rebates offered; rural range anxiety still deters buyers

 

Retired pilot Allan Carlson is used to crossing Labrador by air.

But he recently traversed the Big Land in an entirely new way, driving for hours on end in his electric car.

The vehicle in question is a Tesla Model S P100D, which Carlson says he can drive up to 500 kilometres on a full charge — and sometimes even a little more.

After catching a ferry to Blanc-Sablon, Que., earlier this month, he managed to reach Happy Valley-Goose Bay, over 600 kilometres away.

To get there, though, he had to use the public charging station in Blanc-Sablon. He also had to push the limits of what his car could muster. 

But more affordable mass-market electric vehicles don't have the battery power of a top-of-the-range Tesla, prompting the Big Land's first EV owner to wonder when Labrador infrastructure will catch up to the high-speed charging network recently unveiled across Newfoundland this summer.

Phillip Rideout, an electrician who lives in Nain, bought a Chevrolet Bolt EV for his son — the range of which tops out at under 350 kilometres, depending on driving patterns and weather conditions.

He's comfortable driving the car within Nain but said he's concerned about traveling to southern Labrador on a single charge.

"It's a start in getting these 14 charging stations across the island," Rideout said of Newfoundland's new network, "but there is still more work to be done."

The provincial government continues to push an electric-vehicle future, however, even as energy efficiency rankings trail the national average, despite Labradorians like Rideout feeling left out of the loop.

Bernard Davis, minister of environment and climate change, earlier this month announced that government is accepting applications for its electric-vehicle rebate program, as the N.W.T. EV initiative pursues similar goals.

Under the $500,000 program, anyone looking to buy a new or used EV would be entitled to $2,500 in rebates, an attempt by the provincial government to increase EV adoption.

But according to a survey conducted this year by polling firm Leger for the Canadian Vehicle Manufacturer's Association, 51 per cent of rural Canadians found a lack of fast-charging public infrastructure to be a major deterrent to buying an electric car, even as Atlantic EV interest lags overall, according to recent data.

While Newfoundland's 14-charger network, operated by N.L. Hydro and Newfoundland Power, allows drivers to travel from St. John's to Port aux Basques, and 10 new fast-charging stations are planned along the Trans-Canada in New Brunswick, Labrador in contrast has just two publicly available charging locations: one at the YMCA in Happy Valley-Goose Bay and the other near the town office of Churchill Falls.

This is the proposed second phase of additional Level 2 and Level 3 charging locations across Labrador. (TakeChargeNL)
These are slower, Level 2 chargers, as opposed to newer Level 3 charging stations on the island. A Level 2 system averages 50 kilometres of range per hour, and a Level 3 systems can add up to 250 kilometres within the same time frame, making them about five times faster.

Even though all of the fast-charging stations have gone to Newfoundland, MHA for Lake Melville Perry Trimper is optimistic about Labrador's electric future.

Trimper has owned an EV in St. Johns since 2016, but told CBC he'd be comfortable driving it in Happy Valley-Goose Bay.

He acknowledged, however, that prospective owners in Labrador might not be able to drive far from their home charging outlet. 

More promises
If rural skepticism driven by poor infrastructure continues, the urban population could lead the way in adoption, allowing the new subsidies to disproportionately go toward larger population centres, Davis acknowledged.

"Obviously people are not going to purchase electric vehicles if they don't believe they can charge them where they want to be or where they want to go," Davis said in an interview in early September.

Under the provincial government's Phase 2 proposal, Newfoundland and Labrador is projected to get 19 charging stations, with three going to Labrador in Happy Valley-Goose Bay, Churchill Falls and Labrador City, taking cues from NB Power's public network in building regional coverage.

Davis would not commit to a specific cutoff period for the rebate program or a timeline for the first fast-charging stations in Labrador to be built.

"At some point, we are not going to need to place any subsidy on electric vehicles," he said, "but that time is not today and that's why these subsidies are important right now."

Future demand 
Goose Bay Motors manager Joel Hamlen thinks drivers in Labrador could shift away from gas vehicles eventually, even as EV shortages and wait times persist.

But he says it'll take investment into a charging network to get there.

"If we can get something set up where these people can travel down the roads and use these vehicles in the province … I am sure there will be even more of a demand," Hamlen said.

 

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Solar and wind power curtailments are rising in California

CAISO Renewable Curtailments reflect grid balancing under transmission congestion and oversupply, reducing solar and wind output while leveraging WEIM trading, battery storage, and transmission expansion to integrate renewables and stabilize demand-supply.

 

Key Points

CAISO renewable curtailments are reductions in wind and solar output to balance grid amid congestion or oversupply.

✅ Driven mainly by transmission congestion, less by oversupply.

✅ Peaks in spring when demand is low and solar output is high.

✅ Mitigated by WEIM trades, new lines, and battery storage growth.

 

The California Independent System Operator (CAISO), the grid operator for most of the state, is increasingly curtailing solar- and wind-powered electricity generation, as reported in rising curtailments, as it balances supply and demand during the rapid growth of wind and solar power in California.

Grid operators must balance supply and demand to maintain a stable electric system as advances in solar and wind continue to scale. The output of wind and solar generators are reduced either through price signals or rarely, through an order to reduce output, during periods of:

Congestion, when power lines don’t have enough capacity to deliver available energy
Oversupply, when generation exceeds customer electricity demand

In CAISO, curtailment is largely a result of congestion. Congestion-related curtailments have increased significantly since 2019 because California's solar boom has been outpacing upgrades in transmission capacity.

In 2022, CAISO curtailed 2.4 million megawatthours (MWh) of utility-scale wind and solar output, a 63% increase from the amount of electricity curtailed in 2021. As of September, CAISO has curtailed more than 2.3 million MWh of wind and solar output so far this year, even as the US project pipeline is dominated by wind, solar, and batteries.

Solar accounts for almost all of the energy curtailed in CAISO—95% in 2022 and 94% in the first seven months of 2023. CAISO tends to curtail the most solar in the spring when electricity demand is relatively low (because moderate spring temperatures mean less demand for space heating or air conditioning) and solar output is relatively high, although wildfire smoke impacts can reduce available generation during fire season as well.

CAISO has increasingly curtailed renewable generation as renewable capacity has grown in California, and the state has even experienced a near-100% renewables moment on the grid in recent years. In 2014, a combined 9.0 gigawatts (GW) of wind and solar capacity had been built in California. As of July 2023, that number had grown to 17.6 GW. Developers plan to add another 3.0 GW by the end of 2024.

CAISO is exploring and implementing various solutions to its increasing curtailment of renewables, including:

The Western Energy Imbalance Market (WEIM) is a real-time market that allows participants outside of CAISO to buy and sell energy to balance demand and supply. In 2022, more than 10% of total possible curtailments were avoided by trading within the WEIM. A day ahead market is expected to be operational in Spring 2025.

CAISO is expanding transmission capacity to reduce congestion. CAISO’s 2022–23 Transmission Planning Process includes 45 transmission projects to accommodate load growth and a larger share of generation from renewable energy sources.

CAISO is promoting the development of flexible resources that can quickly respond to sudden increases and decreases in demand such as battery storage technologies that are rapidly becoming more affordable. California has 4.9 GW of battery storage, and developers plan to add another 7.6 GW by the end of 2024, according to our survey of recent and planned capacity changes. Renewable generators can charge these batteries with electricity that would otherwise have been curtailed.

 

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