Answers

1. That's hard to say.

Overall U.S. energy consumption certainly has increased over time, but per capita consumption hasn't necessarily.

Albert Bartlett, a physics professor at the University of Colorado at Boulder and a contributor to the 2003 report "What Every Westerner Should Know about Energy," wrote that, "In the decade of the 1990s, the total consumption of energy in the United States grew 13.1 percent. In that same time period, the total population of the United States grew by 13.1 percent. Per capita annual energy consumption in the United States remained constant through the decade, a remarkable achievement in itself." And according to another recent report by the Energy Department's Energy Information Administration, Americans collectively consumed 1.5 percent more energy, as measured in British thermal units, in 2005 than they did in 2000; over the same period, the population grew 4.8 percent, which suggests Americans are conserving more energy.

But the figures can be contradictory. The same Energy report showed that from 1990 to 1999 the population grew by 12 percent, while energy consumption grew by 14 percent. That suggests per capita consumption did increase somewhat over that decade, contrary to Bartlett's argument. Even if the numbers were consistent, it would be difficult to draw any conclusions about changes in people's habits. There are a variety of factors that influence consumption, one Energy Department analyst noted, including economic productivity rates and weather. The bottom line: there are so many variables in measuring both population size and energy consumption that the exact relationship between the two is open to debate.

2. False.

According to the Energy Department's Solar Energy Technologies Program, the energy that could be harnessed from a 100-square-mile area of Nevada using modestly-efficient commercial photovoltaic technology could supply the United States with all its electricity. The impractical part, of course, would be moving that energy out of Nevada and across the country to where it's needed. Alternatively, if such solar technology were used on abandoned industrial sites in cities throughout the country, it could supply as much as 90 percent of America's electricity needs.

3. Not always.

Natural gas, the cleanest of the fossil fuels, produces no ash and emits far less in the way of carbon dioxide, carbon monoxide, sulfur dioxide and nitrogen oxides than oil and coal. Because natural gas production takes up less space than wind or solar production, it could have less of an impact in some places depending on other environmental factors. According to "What Every Westerner Should Know about Energy," a gas well that is 1 billion cubic feet disturbs half an acre. A 100-300 acre wind farm or a 46-acre solar farm would be required to produce a comparable amount of energy.

4. Sometimes.

This was a significant problem at Altamont Pass in California, the first area in the country to develop a large-scale wind farm in the 1970s. The intense concentration of relatively small wind turbines killed hundreds of raptors per year. But newer wind farms, using fewer, larger turbines that spin above most birds' flight paths, have had a much lower impact. According to a fact sheet by the National Renewable Energy Laboratory, "Birds can fly into wind turbines, as they do with other tall structures. However, conventional fuels contribute to air and water pollution that can have far greater impact on wildlife and their habitat, as well as the environment and human health."

5. False.

Unless you're standing right next to one, you probably won't hear much more than the blowing wind. According to Energy's fact sheet, "An operating modern wind farm at a distance of 750 feet to 1,000 feet is no more noisy than a kitchen refrigerator."

6. True.

According to Energy, every five miles per hour you drive over 60 mph is equivalent to paying an additional 15 cents per gallon for gasoline. Depending on how fast and how aggressively you drive (speeding, rapid acceleration and braking are also bad for the gas gauge), you could save between 12 cents and 82 cents a gallon by just taking it easier.

7. False.

As the Agriculture Department notes in a list of 10 things people can do to reduce their environmental footprint: "It's green not to use green." Sometimes the best thing to do is to do without.