Energy Shift
Animated: 70 Years of U.S. Electricity Generation by Source
The following content is sponsored by the National Public Utilities Council
Animated: 70 Years of U.S. Electricity Generation by Source
Electricity generation in the U.S. has grown exponentially since 1950, going from 2.96 billion kilowatt-hours (kWh) in 1949 to 4.11 trillion kWh in 2021.
With the growth in electricity generation, the U.S. electricity mix has also evolved, especially as clean electricity sources such as nuclear, wind, and solar power grew in use.
In the animated chart by the National Public Utilities Council above, we explore the past 70 years of U.S. electricity generation, following along with the country’s dynamic electricity mix over the decades.
Trends in U.S. Power Generation Since 1950
The U.S. generated 1,200% more electricity in 2021 compared to 1950.
Here’s how the share of each source in the electricity mix changed over that period.
| Year | Coal | Natural Gas | Solar | Wind | Hydro | Nuclear | Other |
|---|---|---|---|---|---|---|---|
| 1950 | 46% | 13% | 0% | 0% | 30% | 0% | 10% |
| 2021 | 22% | 38% | 3% | 9% | 6% | 19% | 3% |
While coal and hydropower led as the largest sources of electricity in the 1950s, the growth in U.S. electricity demand is met primarily by natural gas today, followed by coal, nuclear, and wind power.
Despite coal’s heavy share in the U.S. electricity mix since 1949, its use has declined in recent years, peaking in 2007 in terms of total electricity generated.
With the low cost of natural gas and the advancement of decarbonization efforts, 80+ coal plants have retired or are set to retire in the next three decades in the United States. Despite this, coal remains the largest contributor to power sector emissions, accounting for 58% in 2021.
Besides the rise and fall of coal use, the animation highlights other interesting trends in the country’s power generation over the last 70 years, including:
- Nuclear energy slowly starts contributing to the electricity mix in 1957 as the Shippingport Atomic Power Station comes on in Pennsylvania. By 2020, nuclear power accounts for nearly 20% of total electricity generation.
- Solar and wind power start contributing to the mix in 1983-84, with wind accelerating faster than solar power to account for 1% of total electricity generated by 2008 and 9% by 2021.
- Electricity sourced from natural gas surpasses that from coal in 2016 and continues to absorb most of the decline in coal use through the present day.
- Hydropower’s share in the electricity mix remains stable since 2000, making up 5 to 6% of total electricity generated each year.
The Road to Net-zero
While the decline in coal use for electricity aids in lowering emissions, the U.S. power sector has a long way to go in decarbonizing. In 2021, the use of fossil fuels for power generation contributed 1,537 million tonnes of carbon dioxide emissions in the country.
Therefore, accelerating the deployment of carbon-free energy sources is critical for the road to a decarbonized power sector.
The chart below shows how U.S. electricity generation needs to change to achieve net-zero emissions by 2050.
In the net-zero scenario, Energy Innovation’s policy simulator counts on a complete phase-out of coal-fired electricity by 2034, along with a 36-fold increase in solar power generation and a 10-fold increase in wind power generation by 2050 (compared to 2020 levels.)
The rapid transition from fossil fuels to clean-energy sources, coupled with adequate transmission expansion and investment in battery storage, is integral for a carbon-free power sector. With prompt action, the next 30 years of U.S. electricity generation has the power to look a lot like the projected graph above, giving way to lower emissions for all other sectors that use electricity.
Energy Shift
Mapped: The Age of Energy Projects in Interconnection Queues, by State
This map shows how many energy projects are in interconnection queues by state and how long these projects have been queued up, on average.
U.S. Energy Projects in Interconnection Queues, by State
By the end of 2023, more than 11,000 energy projects were in interconnection queues in the United States, waiting for a green-light from regional grid operators to proceed with construction.
This map, sponsored by the National Public Utilities Council, maps out the average age of active energy projects in interconnection queues by state, using data from Berkeley Lab.
Interconnection Queues, Explained
Interconnection queues are lists of energy projects that have made interconnection requests to their regional grid operators. Once submitted, these requests formally initiate the impact study process that each project goes through before grid connection, forming waiting lists for approval known as interconnection queues.
In recent years, both the number and generation capacity of queued projects have surged in the United States, along with the length of time spent in queue.
According to Berkeley Lab, the amount of generation capacity entering queues each year has risen by more than 550% from 2015 to 2023, with average queue duration rising from 3 years to 5 years the same period.
As a result of the growing backlog, a large proportion of projects ultimately withdraw from queues, leading to only 19% of applications reaching commercial operations.
The Backlog: Number of Projects and Average Wait Times
Of the 11,000 active projects in U.S. queues at the end of 2023, Texas, California, and Virginia had the most in queue; 1,208, 947, and 743, respectively.
When looking at the average ages of these projects, all three states hovered around the national average of 34 months (2.83 years), with Texas sporting 28 months, California 33, and Virginia 34.
Vermont, Minnesota, Wisconsin, and Florida, on the other hand, had the highest average queue durations; 54, 49, 47, and 46 months, respectively.
Average Queue Duration by Project Type
At the end of 2023, more than 95% of the generation capacity in active interconnection queues was for emission-free resources. The table below provides a breakdown.
| Project Type | Average Queue Duration (As of 12/31/2023) | Number of Projects in Queue |
|---|---|---|
| Wind | 40 months | 841 |
| Solar | 34 months | 4,506 |
| Wind+Battery | 34 months | 76 |
| Solar+Battery | 27 months | 2,377 |
| Battery | 24 months | 2,818 |
Wind projects had the highest wait times at the end of 2023 with an average age of 40 months (3.33 years). Solar projects, on the other hand, made up more than 40% of projects in queue.
Overall, reducing the time that these renewable energy projects spend in queues can accelerate the transition to a low-carbon energy future.
According to the U.S. Department of Energy, enhancing data transparency, streamlining approval processes, promoting economic efficiency, and maintaining a reliable grid are some of the ways this growing backlog can be mitigated.
Learn how the National Public Utilities Council is working toward the future of sustainable electricity.
Energy Shift
All Commercially Available Long Duration Energy Storage Technologies, in One Chart
In this chart, we break down the parameters of LDES technologies that have commercial or pre-commercial readiness.
All Commercially Available Long Duration Energy Storage Technologies, in One Chart
Long duration energy storage (LDES) technologies can store electricity for 10+ hours, complementing intermittent renewables, boosting grid resiliency, and reducing fossil fuel dependency.
Created in partnership with the National Public Utilities Council, this chart lists the characteristics of LDES technologies that have commercial or pre-commercial readiness, using data from the LDES Council’s Net-Zero Power report and 2023 deployment update.
The Four Primary Types of LDES
Before getting into the details, let’s cover the four primary types of LDES.
- Mechanical: Stores potential energy (by tension or position)
- Thermal: Stores energy as heat
- Chemical: Stores energy found within chemical bonds
- Electrochemical (batteries): Stores energy of chemical reactions, where electrical energy is converted to chemical energy and vice versa
Currently, mechanical storage systems are the most common around the world. Aboveground pumped hydropower, for instance, currently accounts for 96% of all utility-scale energy storage in the United States.
How Do LDES Technologies Measure Up?
Below, we list the storage capacity, storage duration, and average round-trip efficiency (RTE) of LDES technologies that have commercial or pre-commercial readiness on a global scale.
For context, RTE measures the effectiveness of a storage system by measuring the ratio of energy output to energy input during a full charge-discharge cycle. Or briefly, the higher the RTE, the lower the losses and therefore higher the efficiency.
| Form of Energy Storage | LDES Technology | Storage Capacity (MW) | Nominal Duration (Hours) | Average Round-Trip Efficiency |
|---|---|---|---|---|
| Mechanical | Underground pumped hydro | 10–100 | 0–15 | 50–80% |
| Mechanical | Liquid air | 50–100 | 10–25 | 40–70% |
| Mechanical | Aboveground pumped hydro | 200–400 | 0–15 | 70–80% |
| Mechanical | Liquid CO2 | 10–500 | 4–24 | 70–80% |
| Mechanical | Compressed air | 200–500 | 6–24 | 40–70% |
| Mechanical | Gravity-based | 20–1,000 | 0–15 | 70–90% |
| Thermal | Sensible heat | 10–500 | 200 | 55–90% |
| Chemical | Power-to-gas-to-power | 10–100 | 500–1,000 | 40–70% |
| Electrochemical | Aqueous electrolyte flow battery | 10–100 | 25–100 | 50–80% |
| Electrochemical | Metal anode battery | 10–100 | 50–200 | 40–70% |
| Electrochemical | Hybrid flow battery (with liquid electrolyte and metal anode) | >100 | 8–50 | 55–75% |
The table above shows that a mechanical, gravity-based LDES system can provide the highest storage capacity while presenting an impressive 70–90% average RTE.
On the other hand, a chemical power-to-gas-to-power system, which typically converts electricity to hydrogen gas and back to electricity, provides the highest storage duration of up to 1,000 hours.
With that said, there are different storage needs and siting considerations across electrical grids. Given the diverse range of options available, suitable solutions can be found to complement renewables and aid decarbonization.
Learn how the National Public Utilities Council is working toward the future of sustainable electricity.
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