From California to New Jersey, the summer sun was hot this year — and so was the solar industry. While the business of solar energy is still small enough and young enough to record firsts at the fearsome pace of a toddler, the milestones are getting more substantial.

For instance, in mid-August California’s utility-scale solar generating stations combined to put out the same amount of energy — one gigawatt — as a substantial nuclear or coal-fired power plant. That moment occurred around 1 p.m..

As the energy-related Web site Earth Techling pointed out, the California Independent System Operator only records the solar energy coming from utility-scale facilities, and there is another gigawatt of installed power on rooftops around the state.

The number of megawatts installed in the second quarter of this year was around 742, more than double the 343 megawatts installed in the first quarter of 2011, according to a report released Monday that was commissioned by the Solar Energy Industries Association.



The same report, showed that the United States now has 5.7 gigawatts of installed solar capacity, enough to power one million homes, according to the the report, which was prepared by GTM Research, a Boston-based consulting company.

Then again, even in California, where more than one-third of the new installations were located, the new high-water mark for daily solar power production represents only 1 percent of total demand. Wind energy — which is counter-cyclical with solar energy, as the wind is weakest when the sun shines brightest — represented 3.7 percent of demand on the day of peak solar-energy generation.

Yet more installations are coming. BrightSource Energy’s plant in Ivanpah, in the Mojave Desert just west of the Nevada-California border, is more than half finished; its concentric arrays of mirrors, captured in a series of images in The New York Times Magazine this summer, will generate 392 megawatts of power when it comes online.

A 100-megawatt plant planned in Henrietta, Calif., drew closer to reality last week when Pacific Gas & Electric,the dominant utility in Northern California, announced that it had agreed to buy power from the facility.

It may be worth noting that amid all the news about solar expansion and milestones, the federal Energy Information Administration reported on Monday that energy-related carbon dioxide emissions declined 2.5 percent from 2010 to 2011.

“Electric power generation from natural gas, the least carbon-intensive of the fossil fuels, increased by 3 percent, while generation from coal declined by 6 percent,” the agency reported, noting that carbon dioxide emissions from burning natural gas are around half those that result from burning coal.

“Power generation from renewable sources continued to rise, mostly because of record-breaking supplies of hydroelectricity and increasing generation from wind, solar, and other renewable sources,” the agency’s report added.



An earlier version of this post, relying on a chart from the California Independent System Operator, misstated the time at which solar power generation peaked in California on Aug. 14. It was at 12:59 p.m., not between 5 and 6 p.m.