Charts: See when renewables provide more than 20% of power in the US

Canary Media’s chart of the week translates crucial data about the clean energy transition into a visual format.

How best to understand the remarkable growth of clean energy on U.S. power grids over the past four years? Let’s take a look at it season by season. 

That’s what the Institute for Energy Economics and Financial Analysis has done with two charts tracking utility-scale wind, solar and hydropower as a share of U.S. electricity generation from 2019 to 2022. Using data from the Energy Information Administration’s Hourly Grid Monitor, IEEFA calculated the day-by-day share of these carbon-free resources as a percentage of total U.S. generation.

IEEFA’s data paints a remarkable picture of clean-energy growth, as the bands of green in the chart above illustrate. Renewables exceeded 20 percent of total U.S. generation during 191 days in 2022, more than triple the 63 days in 2019. During five days last spring, renewables constituted between 30 and 35 percent of total generation.

Spring is when relatively abundant sun, wind and water coincide with relatively low demand for electricity. Those are ideal conditions for the country’s fast-growing solar and wind resources to displace power generation from coal and fossil-gas power plants.

But during the hot summer, demand for electricity to run air conditioning spikes across the country. Because much of this AC-driven demand comes later in the day as the supply of solar power is fading, fossil-fuel power plants are fired up to supply it. That’s why summer months on IEEFA’s chart are dominated by gray bands, representing days when clean energy provided less than one-fifth of total U.S. electricity demand.

Renewables are now supplying a greater share of power in fall and winter. In 2022, renewables broke 20 percent of total generation during 40 days of the fall months and 31 days in January and February, compared to only four days during each of those periods in 2019. And as the chart below shows, renewables have been out-generating coal-fired power during a significant number of days over the past few years. 

But the data does highlight the fact that clean energy output varies with the weather — and that the sum total of U.S. generation capacity remains only one side of the supply-demand equation. Balancing an increasingly renewable-powered grid will require lots of batteries to shift solar and wind power into higher-demand hours of the day, long-duration energy storage to cover longer periods of low wind and sun, and a host of other technologies that can better match when people use electricity to when the sun, wind and water provide it.