Earth Day has reached middle age. As Americans celebrate our planet for the 48th time today, it's worth reflecting for a moment on how far the nation has come in its views on energy and the environment. What was once a protest against the establishment is now mainstream.

A recent Gallup poll revealed that 59 percent of the American public favors prioritizing environmental protection over domestic energy production. No less than 56 percent placed environmental protection above economic growth as a priority. Renewable energy is even more popular. Seventy-nine percent of those polled would like the United States to place more emphasis on solar power, and only 9 percent wanted less. For wind power, 70 percent said more and 14 percent, less.

A majority of Trump voters belong to this mainstream as well. Surveys conducted after the 2016 election by researchers at Yale and George Mason Universities show that 69 percent of these voters support tax rebates for those who purchase energy efficient vehicles and solar panels, while 52 percent would like to eliminate federal subsidies for the coal, oil, and natural gas industries.

These majorities are increasingly putting their money where their mouths are. According to the Business Council on Sustainable Energy, solar and wind power accounted for roughly 70 percent of new electricity generation capacity in the United States last year. The nation surpassed a million solar installations last year as well, with some 30,000 added each month. When a customer can walk into a Home Depot, as I did recently in suburban Washington, D.C., and find a solar installer with a booth on the premises ready to quote a firm price for immediate installation, you know that what was once "alternative energy" is now mainstream.

None of this means that the environment is safe. Clean water is not assured in the United States, as residents of Flint, Michigan can attest. The American Lung Association reports that 166 million Americans live in places with unhealthful levels of air pollution. The threat of climate change is becoming more real with each passing day, endangering both urban and rural ways of life in this country.

Nor do most Americans fully understand what protecting the environment entails. Basic questions about scientific facts and how scientists know that facts are facts trip people up. The essentials of running an electric grid that supplies the affordable, reliable power that the average person takes for granted are a complete mystery to him.

But the mainstreaming of what was once "alternative" provides the foundation of public support upon which an energy system that truly protects the environment can be erected. Americans are telling survey researchers that they are open to change and they want choice when they use energy. And they are using their wallets to reinforce this message.

Our nation probably won't ever run entirely on renewable resources. Nor will rooftop solar systems fully supplant big power plants. In fact, "diversity" may be the word that best characterizes America's energy system in the 21st century, just as it does our 21st century society. The diverse ways that we use energy—like heating, lighting, transportation, industry—will be supplied by equally diverse resources. Energy demand and supply will be matched in sophisticated ways by applying the latest digital technologies. Digital technologies will also help us to use only as much energy as we need for the service we want and dramatically reduce the amount that we waste.

Diversity will make the energy system of the future at least as affordable and reliable as today's, and much, much cleaner. The flexibility of this system will also make possible a stream of innovations that will continually improve it. We can only dimly sketch what the future will bring in this regard: smart grids, smart cars, smart buildings, and smart cities that work together to maximize energy efficiency and environmental protection while serving human needs.

What we need now to bring this bright future to pass is wise leadership. The entrepreneurs and innovators are ready, but government must reformulate its approach to energy policy in order to unlock their vast potential. Regulation must get smarter. Tax incentives must reward innovators, not incumbents. Public investment must flow to research and technology that hold great promise but are too risky for the private sector to invest in yet.

If the politicians and policy wonks do their jobs well, future Earth Days will be celebrations of our own diversity as well as of our unique, precious planet.

David Hart (@ProfDavidHart) is a senior fellow at the Information Technology and Innovation Foundation, the leading U.S. science and tech policy think tank, and professor of public policy and director of the Center for Science and Technology Policy at George Mason University's Schar School of Policy and Government.

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