Liz Robinson long ago reconciled herself to the naysayers, the folks who thought that green jobs were some figment of a tree hugger's imagination.

"I think people don't understand," said Robinson, executive director of the Energy Coordinating Agency, a Philadelphia nonprofit that trains people to perform energy audits on houses and buildings in the city.

Maybe more will now. On Thursday, the mother source of all job statistics, the office that provides research data to battalions of labor economists and academicians, released its first report on green jobs and services.

The U.S. Labor Department's Bureau of Labor Statistics (BLS) reported that there were 3.1 million green jobs nationwide in 2010, or 2.4 percent of total employment.

Of those jobs, 182,193 were in Pennsylvania, making it one of the five highest states in the country in generating green employment, compared to 76,025 in New Jersey and 7,978 in Delaware.

Manufacturers producing hybrid cars, solar panels, and other products created the most jobs, 461,847, with construction, professional and technical services, waste services including recycling, and transportation and warehousing being other green-job generators.

This report was not the first to try to measure green jobs. Pennsylvania's Department of Labor and Industry authored one in 2010. And the Brookings Institute, the nonprofit Washington research organization, released its own data in July, putting the number of jobs at 2.7 million.

"The BLS has far more resources than any think tank can bring to bear on this kind of economic study," said Jonathan Rothwell, a senior research analyst on the Brookings report. "They've done it in a way that experts agree is the best possible way, because it is attached to the way we measure the economy across all kinds of sectors. Their long expertise ... does give it a certain imprimatur that is at least notable."

In introducing its July report, the Brookings Institute made the point that it is hard to define, isolate and quantify green jobs.

The BLS did it by identifying 333 industries from the 1,193 listed in the North American Industry Classification System, the Dewey Decimal System of business organization. It looked at five broad categories of production and service:

â ¢Energy from renewable sources.

â ¢Energy-efficient equipment, appliances, buildings or vehicles, or items that improve their efficiency or improve the efficiency of energy distribution.

â ¢Pollution reduction, recycling, and reuse.

â ¢Organic agriculture and sustainable forestry.

â ¢Government administration, education, training and advocacy.

Rothwell said that the BLS methodology basically mirrors Brookings' work, and that analysts are reaching a consensus over definitions. But the details are interesting.

For example, the BLS, Rothwell said, counts workers who repair hybrid cars; Brookings does not. The BLS counts government regulators; not Brookings.

Neither Brookings nor the BLS includes chefs who work in organic restaurants. Why? Because whether they're chopping organic onions or regular ones, onions are onions.

BLS had access to company-revenue data, Rothwell said. If 60 percent of a company's revenues came from green products, the bureau considered 60 percent of the employees green.

The report comes at a critical time, said Cai Steger, an energy-policy analyst at the Natural Resources Defense Council, a New York-based environmental group. "As the conversation politically has grown contentious," he said, "it's really ... to add data and facts to the conversation."

Robert Stoy counts himself as working one of the 3.1 million green jobs. In 2007, he was a residential-construction manager. When the housing market tanked, he lost his job, and later lost a similar job in commercial construction, when contracts dried up.

Now, he's an energy auditor with a small business, Start Smart Energy Use L.L.C. in Newtown Square. His business, analyzing homes for energy efficiency, nowhere near equals what he earned in construction. But that work doesn't exist now, and Stoy is optimistic about the future of his new field.

"The sky's the limit," he said.

Contact Jane M. Von Bergen at 215-854-2769, or @JaneVonBergen on Twitter. Read her Jobbing blog at