What the year’s longest day means for solar

By Benjamin Storrow | 06/21/2024 06:16 AM EDT

The summer solstice offers an annual benchmark for the booming industry.

Workers install solar panels at the Port of Los Angeles.

Friday is expected to be one of the biggest days of the year for solar energy generation. Mario Tama/Getty Images

It’s the high time of the year for solar energy.

The sun is expected to account for 20 percent of global electricity production when it reaches its peak Friday — the summer solstice in the Northern Hemisphere, according to a report by Ember, a clean energy consulting firm. That’s up 4 percent over last year’s peak.

The longest day of the year is an annual high water mark for solar production. It represents a snapshot in time, as solar generation will slowly wane as the days gradually become shorter until the winter solstice in December. Ember’s findings nevertheless underscore the industry’s rapid growth. Global solar generation has ballooned from around 130 terawatt-hours in 2013 to 1630 TWh in 2021, Ember found.


The industry is poised for more growth in the coming years. The International Energy Agency recently estimated that the $500 billion that’s expected to be invested globally on solar this year beats the spending on all other forms of power generation combined.