How Did the Grid Become Cleaner?

This week’s columns are on the carbon dioxide emissions of the U.S. and the world’s electric grids, fitting if only because next Monday is Earth Day.

Tuesday’s column addressed: how clean was the U.S. grid in 2018 relative to other countries’ grids? Wednesday’s column addressed: by how much did the U.S. grid clean since 2000?

The question for today’s column is, how did the U.S. grid become cleaner?

Grid emissions were high in the year before the U.S. went into the great recession, 2007. Coal generation was at the historic record of 2,016 million megawatt-hours.

Emissions were also high in the year when Hurricane Katrina caused so much destruction, 2005, and also drove up natural gas prices. Coal generation was near the historic record set in 2007, 2,013 million megawatt-hours. And oil generation spiked to levels not seen since the early 1990’s.

Let’s use the more recent year, 2007, as the benchmark to see how we got to 2018 in eleven years.

Total grid generation was virtually identical in the two years. In 2007, it was 4,157 million megawatt-hours and in 2018, it was 4,178 million. An increase of just 21 million megawatt-hours, or half a percent.

But coal generation fell from 2,016 million megawatt-hours to 1,146 million. A decrease of a huge amount, 870 million megawatt-hours, or forty-three percent.

What did the grid substitute in for this 870 million megawatt-hour hole?

Well, natural gas generation rose from 897 million megawatt-hours to 1,468 million. An increase of 571 million megawatt-hours, or sixty-four percent.

This is a whole lot. But around 300 million megawatt-hours of the hole remains.

Feel breezy in here? Hint. Wind generation rose from a measly 34 million megawatt-hours in 2007 to 275 million in 2018. Wow. An increase of 241 million megawatt-hours, or seven hundred and nine percent.

There were other significant changes in the grid’s generation. Solar was up by 66 million megawatt-hours, hydro was by 44 million, while oil was down by 41 million. Nuclear held steady, up by 1 million, despite recent plant closures.

So, from 2007 to 2018, we burned much less coal and oil to generate electricity, burned more natural gas to fill a good part of the gap, and filled much of the remainder with wind.