Decarbonization Channel

At all times, the amount of electricity generated must match demand in order to keep the power grid in balance, which leads to cyclical patterns in daily and weekly electricity generation.

The above graphic sponsored by the National Public Utilities Council tracks hourly changes in U.S. electricity generation over one week, based on data from the U.S. Energy Information Administration (EIA).

The Three Types of Power Plants

Before diving in, it’s important to distinguish between the three main types of power plants in the U.S. electricity mix:

Base load plants generally run at full or near-full capacity and are used to meet the base load or the minimum amount of electricity demanded at all times. These are typically coal-fired or nuclear power plants. If regionally available, geothermal and hydropower plants can also be used as baseload sources.
Peak load or peaking power plants are typically dispatchable and can be ramped up quickly during periods of high demand. These plants usually operate at maximum capacity only for a few hours a day and include gas-fired and pumped-storage hydropower plants.
Intermediate load plants are used during the transitory hours between base load and peak load demand. Intermittent renewable sources like wind and solar (without battery storage) are suitable for intermediate use, along with other sources.

Zooming In: The U.S. Hourly Electricity Mix

With that context, the table below provides an overview of average hourly electricity generation by source for the week of March 7–March 14, 2023, in the Eastern Time Zone.

It’s worth noting that while this is representative of a typical week of electricity generation, these patterns can change with seasons. For example, in the month of June, electricity demand usually peaks around 5 PM, when solar generation is still high, unlike in March.

Energy Source	Type	Avg. Hourly Electricity Generation, MWh (Mar 07–14, 2023, EST)
Natural Gas	Fossil fuel	175,967
Nuclear	Non-renewable	84,391
Coal	Fossil fuel	71,922
Wind	Renewable	50,942
Hydro	Renewable	28,889
Solar	Renewable	13,213
Other	Mixed	8,192

Natural gas is the country’s largest source of electricity, with gas-fired plants generating an average of 176,000 MWh of electricity per hour throughout the week outlined above. The dispatchable nature of natural gas is evident in the chart, with gas-fired generation falling in the wee hours and rising during business hours.

Meanwhile, nuclear electricity generation remains steady throughout the given days and week, ranging between 80,000–85,000 MWh per hour. Nuclear plants are designed to operate for long durations (1.5 to 2 years) before refueling and require less maintenance, allowing them to provide reliable baseload energy.

On the other hand, wind and solar generation tend to see large fluctuations throughout the week. For example, during the week of March 07–14, wind generation ranged between 26,875 MWh and 77,185 MWh per hour, based on wind speeds. Solar generation had stronger extremes, often reaching zero or net-negative at night and rising to over 40,000 MWh in the afternoon.

Because wind and solar are often variable and location-specific, integrating them into the grid can pose challenges for grid operators, who rely on forecasts to keep electricity supply and demand in balance. So, what are some ways to solve these problems?

Solving the Renewable Intermittency Challenge

As more renewable capacity is deployed, here are three ways to make the transition smoother.

Energy storage systems can be combined with renewables to mitigate variability. Batteries can store electricity during times of high generation (for example, in the afternoon for solar), and supply it during periods of peak demand.
Demand-side management can be used to shift flexible demand to times of high renewable generation. For instance, utilities can collaborate with their industrial customers to ensure that certain factory lines only run in the afternoon, when solar generation peaks.
Expanding transmission lines can help connect high-quality solar and wind resources in remote regions to centers of demand. In fact, as of the end of 2021, over 900 gigawatts of solar and wind capacity (notably more than the country’s current renewable capacity) were queued for grid interconnection.

Click here to learn more about how electric utilities and the power sector can lead on the path toward decarbonization.

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Visualized: How the Power Grid Works

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Electrification

Visualized: How the Power Grid Works

How does electricity get from the power plant to our homes? This infographic illustrates how the power grid works.

Published

7 months ago

on

November 7, 2022

By

Govind Bhutada

How Does the Power Grid Work?

Electricity is critical to our daily lives, but how does it get from the power plant to our homes?

The power grid is a complex interconnected system that powers the entire economy by carrying electricity from the source of generation and delivering it to our homes, offices, and factories. Sometimes referred to as “the world’s largest machine”, the grid is an important engineering marvel for the modern economy.

The above infographic from the National Public Utilities Council explains how the power grid works and highlights the three key components that make up the grid.

#1: Electricity Generation

The grid begins with power plants that generate electricity, typically owned and operated by public, private, or investor-owned utilities.

More than 11,000 power plants comprise the U.S. grid, generating over 4 trillion kilowatt-hours (kWh) of electricity annually. These are fueled by various energy sources:

Energy Source	2021 Electricity Generation (billion kWh)	% of Total
Natural Gas	1,575	38%
Coal	899	22%
Nuclear	778	19%
Renewables	826	20%
Other	38	0.9%
Total	4,116	100%

Source: Energy Information Administration (EIA)

Natural gas and coal together accounted for 60% of annual electricity generation in 2021, followed by nuclear power. Wind was the largest renewable energy source, making up 10% of renewable electricity generation.

Each power generation technology has a different role to play in the larger power grid. For example, coal and nuclear power plants that cannot easily adjust their output are known as baseload power plants. Their output remains roughly the same throughout the day, and they are typically used to deliver the minimum amount of power needed to keep the grid running.

On the other hand, power generation from natural gas and intermittent renewable sources like wind and solar fluctuates throughout the day, typically peaking in the evenings when demand is at its highest. Natural gas plants are especially useful in meeting peaks in demand because their output can be adjusted relatively quickly.

#2: Transmission

After generation, electricity travels from power plants to centers of demand through a process known as transmission.

First, the electricity is sent from power plants to substations where step-up transformers convert it to extremely high voltages for transmission. High-voltage conversions help minimize how much electricity is lost as heat during transmission, which is roughly 5% in the United States. The higher the voltage, the less electricity is lost.

Transmission lines then carry this high-voltage electricity across long distances and are often interconnected across states. Line voltages can vary from 69,000 volts (69 kV) to 765kV, and transmission lines can be both overhead and underground.

Here’s a map of all high-voltage (345kV or greater) U.S. transmission lines:

Source: U.S. Energy Atlas

Upgrading and expanding transmission infrastructure is key to achieving a decarbonized power grid, especially as utilities build solar and wind capacity in the sunniest and windiest parts of the country.

#3: Distribution and Consumption

Distribution is the final stage of delivering electricity, making up the last major component of the grid.

Simply put, distribution begins when transmission ends. It is the process of transporting power from the transmission system to individual customers. First, step-down transformers convert the high-voltage power from transmission lines into lower voltages that are suitable for use.

These transformers are connected to distribution poles, which are typically made of wood and used to carry electricity within centers of demand. There are about 180 million distribution poles in the U.S., and it’s likely that you encounter one every day, especially if you live in a city.

Distribution lines and poles deliver electricity to end consumers including households, office buildings, factories, and electric vehicles. Here’s a look at U.S. electricity sales to each end-use sector in 2021:

Sector	2021 retail electricity sales (billion kWh)	% of Total
Residential 🏠	1,480	39%
Commercial 🏢	1,320	35%
Industrial 🏭	987	26%
Transportation 🚙	6	0.2%
Total	3,793	100%

Source: EIA

Heating and cooling are the largest residential electricity uses. In the commercial sector, refrigeration and computers and office equipment account for over a quarter of electricity use. The transportation sector is by far the smallest electricity consumer, but these figures may change as electric vehicle sales rise.

At all times, the amount of electricity sent through the grid must match demand from end-use sectors. This is because all grids operate at a particular frequency (60 hertz in the United States). Excess power supply or demand can destabilize this frequency, potentially damaging grid infrastructure and triggering blackouts.

Modernizing the Power Grid

Just like machines that get old and need greasing, the U.S. power grid is aging and it needs an upgrade, especially as the power sector works to achieve 100% clean electricity by 2035.

The demand for electricity could accelerate in a scenario with high electrification, which involves switching from fossil fuel-powered technologies to electrical ones. For instance, one form of electrification is switching from gas-powered cars to electric cars.

To meet the growing demand for electricity, especially from clean energy sources, the U.S. will need to expand its transmission capacity and invest in modernizing the grid. In fact, reaching 100% clean electricity by 2035 could require anywhere from $330 billion to $740 billion in additional power system expenditures, according to a study by NREL.

Ultimately, upgrading and decarbonizing the grid are both pivotal to the U.S.’ climate goals, and this requires action from all stakeholders, from electric utilities to the government and end consumers.

The National Public Utilities Council is a collaborative body of industry experts coming together to solve decarbonization challenges in the power sector and the proud sponsor of the Decarbonization Channel.

Energy

Ranked: Emissions per Capita of the Top 30 U.S. Investor-Owned Utilities

Published

7 months ago

on

November 6, 2022

By

Aran Ali

Emissions per Capita of the Top 30 U.S. Investor-Owned Utilities

Approximately 25% of all U.S. greenhouse gas emissions (GHG) come from electricity generation.

Subsequently, this means investor-owned utilities (IOUs) will have a crucial role to play around carbon reduction initiatives. This is particularly true for the top 30 IOUs, where almost 75% of utility customers get their electricity from.

This infographic from the National Public Utilities Council ranks the largest IOUs by emissions per capita. By accounting for the varying customer bases they serve, we get a more accurate look at their green energy practices. Here’s how they line up.

Per Capita Rankings

The emissions per capita rankings for the top 30 investor-owned utilities have large disparities from one another.

Totals range from a high of 25.8 tons of CO₂ per customer annually to a low of 0.5 tons.

Utility	Emissions Per Capita (CO2 tons per year)	Total Emissions (M)
TransAlta	25.8	16.3
Vistra	22.4	97.0
OGE Energy	21.5	18.2
AES Corporation	19.8	49.9
Southern Company	18.0	77.8
Evergy	14.6	23.6
Alliant Energy	14.4	14.1
DTE Energy	14.2	29.0
Berkshire Hathaway Energy	14.0	57.2
Entergy	13.8	40.5
WEC Energy	13.5	22.2
Ameren	12.8	31.6
Xcel Energy	11.9	43.3
Duke Energy	11.1	88.9
Dominion Energy	11.0	37.8
Emera	11.0	16.6
PPL Corporation	10.7	29.6
PNM Resources	10.0	5.3
American Electric Power	9.2	50.9
Consumers Energy	8.7	16.1
NRG Energy	8.2	29.8
Florida Power and Light	8.0	41.0
Portland General Electric	7.6	6.9
Fortis Inc.	6.1	12.6
Avangrid	5.1	11.6
PSEG	3.9	9.0
Exelon	3.8	34.0
Consolidated Edison	1.6	6.3
Pacific Gas and Electric	0.5	2.6
Next Era Energy Resources	0	1.1

PNM Resources data is from 2019, all other data is as of 2020

Let’s start by looking at the higher scoring IOUs.

TransAlta

TransAlta emits 25.8 tons of CO₂ emissions per customer, the largest of any utility on a per capita basis. Altogether, the company’s 630,000 customers emit 16.3 million metric tons. On a recent earnings call, its management discussed clear intent to phase out coal and grow their renewables mix by doubling their renewables fleet. And so far it appears they’ve been making good on their promise, having shut down the Canadian Highvale coal mine recently.

Vistra

Vistra had the highest total emissions at 97 million tons of CO₂ per year and is almost exclusively a coal and gas generator. However, the company announced plans for 60% reductions in CO₂ emissions by 2030 and is striving to be carbon neutral by 2050. As the highest total emitter, this transition would make a noticeable impact on total utility emissions if successful.

Currently, based on their 4.3 million customers, Vistra sees per capita emissions of 22.4 tons a year. The utility is a key electricity provider for Texas, ad here’s how their electricity mix compares to that of the state as a whole:

Energy Source	Vistra	State of Texas
Gas	63%	52%
Coal	29%	15%
Nuclear	6%	9%
Renewables	1%	24%
Oil	1%	0%

Despite their ambitious green energy pledges, for now only 1% of Vistra’s electricity comes from renewables compared to 24% for Texas, where wind energy is prospering.

Based on those scores, the average customer from some of the highest emitting utility groups emit about the same as a customer from each of the bottom seven, who clearly have greener energy practices. Let’s take a closer look at emissions for some of the bottom scoring entities.

Utilities With The Greenest Energy Practices

Groups with the lowest carbon emission scores are in many ways leaders on the path towards a greener future.

Exelon

Exelon emits only 3.8 tons of CO₂ emissions per capita annually and is one of the top clean power generators across the Americas. In the last decade they’ve reduced their GHG emissions by 18 million metric tons, and have recently teamed up with the state of Illinois through the Clean Energy Jobs Act. Through this, Exelon will receive $700 million in subsidies as it phases out coal and gas plants to meet 2030 and 2045 targets.

Consolidated Edison

Consolidated Edison serves nearly 4 million customers with a large chunk coming from New York state. Altogether, they emit 1.6 tons of CO₂ emissions per capita from their electricity generation.

The utility group is making notable strides towards a sustainable future by expanding its renewable projects and testing higher capacity limits. In addition, they are often praised for their financial management and carry the title of dividend aristocrat, having increased their dividend for 47 years and counting. In fact, this is the longest out of any utility company in the S&P 500.

A Sustainable Tomorrow

Altogether, utilities will have a pivotal role to play in decarbonization efforts. This is particularly true for the top 30 U.S. IOUs, who serve millions of Americans.

Ultimately, this means a unique moment for utilities is emerging. As the transition toward cleaner energy continues and various groups push to achieve their goals, all eyes will be on utilities to deliver.

The National Public Utilities Council is a collaborative body of industry experts coming together to solve decarbonization challenges in the power sector and the proud sponsor of the Decarbonization Channel.