We keep hearing that renewable energy is booming in the United States, but where is it? Here’s a handy map from the U.S. Energy Information Administration showing how much electricity each state gets from wind, solar, biomass, and geothermal (but not hydropower):

Maine was the clear winner in 2011, getting 27 percent of its electricity coming from renewable sources — a lot of it wind power and biomass. But Maine had a lot of renewable energy back in 2001, too. South Dakota and Iowa, at 21 percent and 17 percent, have seen far more impressive growth. Both of those states got almost none of their electricity from renewable sources a decade ago.

Why do some states do better than others? Policy helps. Some 30 states have laws that require utilities to get a certain portion of their power from renewable sources. (The Southeast is the big exception here.) The strictness of the laws varies from state to state, but by and large, states with stricter standards get more renewables. But simply having natural resources helps, too: Idaho, Wyoming, and South Dakota don’t have strict standards, but there’s so much wind up there that turbines are going up anyway.

What’s less clear is whether this rapid growth will continue. A good portion of the recent boom in wind and solar power has been thanks to the federal production tax credit and assorted grants in the stimulus bill. Those grants have now expired and the tax credit for wind will expire at the end of 2012. Clean-energy advocates are hoping it gets renewed when Congress tries to avert “Taxmageddon” and the end of this year, but that’s not a sure bet.

Meanwhile, the EIA notes, if you include hydropower, some states in the Pacific Northwest look even better. Idaho gets 93 percent of its electricity from hydroelectric dams. Oregon gets 78 percent and Washington 82 percent. Hydropower tends to get short shrift whenever talk turns to renewables because it’s generally assumed that there’s no more room for growth — all the big dams have been built already. But this isn’t entirely true. A recent report from the Department of the Interior found that there are all sorts of smaller existing dams around the country that could be put to work and generate an additional 1.5 million MWh of electricity, enough to power a small city.

Update: Commenter BertEisenstein points out that looking at what percent of a state’s electricity is renewable only gives part of the picture, since a small state like Maine with relatively few wind turbines can look better than a huge state like Texas that has many more turbines.

That’s a fair point. The EIA has data on total renewable generation, not including hydropower, here (Excel file). The top states in 2012 on this metric were:

1. Texas
2. California
3. Iowa
4. Minnesota
5. Washington
6. Illinois