More Americans are now installing solar panels on building rooftops than mining coal or extracting oil and gas, according to a report released Tuesday by the non-profit solar advocacy group The Solar Foundation.

The shift is a profound one that highlights how U.S. clean energy, both solar and wind, have emerged as large and rapidly growing sectors. It also shows how many traditional fossil fuel industries like coal and oil have struggled to expand in recent years.

The U.S. solar industry grew dramatically in 2015, and is expected to continue to do so this year. The industry now employs 209,000 workers after adding over 35,000 jobs last year. By the end of this year, its ranks are expected to grow to 240,000 workers.

The solar sector employs 77% more workers than the U.S. coal mining industry does today, according to The Solar Foundation report. The coal industry now employs a little less than 70,000 workers, notes the report.

According to the Bureau of Labor Statistics, there were 185,000 workers employed in the business of extracting oil and gas in the U.S. as of the end of 2015. These workers operate and develop oil and gas fields.

However there are still many more workers employed in the oil and gas sectors in the U.S. than in the solar sector. Employment numbers for the oil industry are notoriously tricky to calculate because of the variety of direct and indirect jobs in the field. But by conservative numbers there are still millions of oil and gas jobs, many of them performing support activities for oil and natural gas operations, like exploration, excavation, well surveying and construction.

Most of the new solar jobs are for installers who mount solar panels on the roofs of homes. Large employers in the U.S. include SolarCity SCTY , Sunrun RUN , and Vivint Solar (acquired by SunEdison . Other jobs in the solar sector include selling and marketing solar contracts, developing large solar projects for utilities, and working in solar panel factories.

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Technicians working on solar panels. Photograph Sam Diephuis — Getty Images

While the sheer numbers of solar workers is large, it’s the growth rate that’s more impressive. The solar industry’s employment has grown 123% since 2010. It grew 20.2% just over the past year.

Last year, the solar sector added workers at a rate that was almost 12 times faster than the overall economy, says the report. In fact, 1.2% of all jobs—or 1 in 83 jobs—created in the U.S. last year were solar jobs.

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This year, solar industry employment is expected to grow another 14.7%, or 15 times faster than the overall economy’s predicted expansion. Rapid growth is expected to continue for the next couple of years.

Just recently, an important federal government incentive that supports the solar sector was extended. Without the extension, the solar industry could have slowed down in 2017 and beyond.

The growth in solar jobs is partly due to the drop in solar panel prices in recent years, which makes them more affordable to consumers and businesses. At the same time, companies like SolarCity have created financing options that enable customers to avoid paying the large upfront fees to install panels.

While the U.S. solar industry is growing, some of the traditional fossil fuel industries are either contracting or growing less quickly than solar. Over the past five years, the coal mining sector has been hit hard partly because of increased federal and state regulation that incentivizes cleaner electricity, like from natural gas and solar.

Meanwhile, over the past year, the oil sector has shed jobs amid rock bottom oil prices. The number of active oil and gas rigs in the U.S. has fallen 61% to 698 compared to a year earlier.