The renewable energy and energy efficiency industries currently consist of about 8.5 million jobs and about $1 trillion in revenue. But if demand continues, that could turn into 40 million jobs and $4.5 trillion in revenues in the next 20 years – in addition to lessening human impact on the environment.

The American Solar Energy Society said that as many as one in four workers could work in these fields by 2030. Particularly hot fields of growth will center around solar, wind, ethanol and fuel cell technology.

However, all this depends on the cycle of demand and growth, or in this case, increasing investing and public policy. Many states and even cities have demanded that renewables play a stronger role in their energy portfolios, which in turn encourages large public utilities to adopt such technologies. This cycle is crucial to lessening people's impact on the environment, so congrats to communities and companies that have worked to bring us to this point.