1. How much solar energy reaches the Earth's surface at any given moment? 173,000 terawatts
2. Of all new generating capacity added to the U.S. electrical grid in 2015, what percentage was solar? 29.4 percent
3. Which U.S. state generates the most utility-scale solar power? California.
4. Roughly how much did the cost of PV solar panels decrease between 2008 and 2015? 80 percent
5. What form of energy do concentrating solar power technologies use to generate electricity? Thermal