Two years in the making, the Topaz Solar Project, the world’s largest, has begun operating in California, powerful enough to supply 160,000 homes using 9 million photovoltaic solar panels installed across 9.5 square miles. Compared to fossil fuel technology, the facility is projected to remove 377,000 tons of carbon dioxide each year; equivalent to taking 73,000 cars off the road. Unlike some solar plants, Topaz requires no water to generate electricity and makes minimal sound because there are no moving parts, so its total environmental impact is minimal.

In Hawaii, where 12 percent of homes have solar panels, handling surplus power is putting pressure on the state’s biggest utility, which now wants to reduce what it pays for the energy. Electricity there is pricey, with monthly bills of $600 to $700 not uncommon. The growing popularity of making electricity at home puts new pressures on old infrastructure like circuits and power lines and cuts into electric company revenue. As a result, many utilities are reducing incentives and adding steep fees. “Hawaii is a postcard from the future,” says Adam Browning, executive director of Vote Solar, a policy and advocacy group based in California.