Ultimately, human civilization will have to be powered mainly by solar energy. Luckily, the sun provides more energy to the earth in an hour than humanity currently consumes in a year. But how long will it take to develop the technology and systems needed to truly harness solar power, and how much will doing so cost? Sivaram’s enlightening and candid book describes both the enormous progress that has already been made in exploiting solar energy in its two major forms—photovoltaic and concentrated solar power—and the major obstacles to further progress. The author worries that existing silicone-based photovoltaic solar panels will “lock out” those made with newer, cheaper, and more effective materials, such as perovskite. Sivaram, a scientist with practical experience advising city governments on energy policy, argues that solar power cannot realize its full potential without significant innovations in power generation, power storage, grid management, financing, and regulation. All of these are achievable with sufficient imagination and money, so he pleads for more R & D funding and fewer subsidies for existing solar installations.