When I’m asked about the pros and cons of different sources of electricity generation, I often emphasize the importance of reliability. America’s daily baseload power needs are enormous, and when it comes to vital infrastructure such as water treatment, hospitals, and public transit, there’s little room for error when making sure that electricity keeps reaching where it’s needed, day in and day out.
A good way to look at this is the real-time data that’s publicly available for some of the nation’s largest utilities. For example, The Midcontinent Independent System Operator (MISO)—which oversees 200,000 megawatts of power-generation across 15 U.S. states—publishes a continuously updated chart of the ‘Fuel Mix’ for its overall power generation.
We can glean some interesting items from MISO’s fuel chart.
For starters, coal continues to be the dominant electricity producer for their mix—averaging about 55 percent of total power generation. Natural gas comes in second at around 17 percent, with nuclear third at about 16 percent.
The remainder of MISO’s energy portfolio comes from wind generation, plus a small sliver of miscellaneous sources.
What’s interesting are the fluctuations in the overall mix. For example, on Thursday, November 29—a cold day for much of the central United States—MISO’s fuel mix showed that wind generation remained at around 2 percent of total generation. This was unfortunate, since the weather was particularly cold—and families were turning up their thermostats to stay warm. But there simply wasn’t much wind blowing throughout most of the day.
By contrast, a few days later, on Monday, December 3, the weather was milder, and wind generation across MISO’s grid was averaging roughly 8 percent of total generation. That’s quite a difference from four days prior.
The point is, while wind generation has some positives in terms of being a “free” source of power, it also has drawbacks. When MISO’s wind capacity declined to 2 percent of total output on November 29, coal and natural gas plants needed to ramp up in order to cover the difference. This generally isn’t a problem, since MISO maintains a sturdy fleet of both coal and gas plants that can run continuously.
But it illustrates a wider point. Renewables are inherently unpredictable—since wind turbines depend on a steady flow of wind, and solar panels require ample, direct sunlight. When the wind isn’t blowing, or the sun isn’t shining, another source of electricity generation is required to make up the difference. and that’s where coal, natural gas, and nuclear plants fill in the gaps.
For these reasons, an “all of the above” energy strategy makes sense, simply to ensure that there are always available means to produce the on-demand electricity that Americans need in order to maintain healthy, safe daily living.