This chapter begins the middle section of the book, in which Gates examines the main categories of human activities that create greenhouse gases—activities that we must address to get to zero emissions. He starts with electricity, which accounts for about a quarter of annual carbon emissions. Even though it isn’t the greatest share, what makes electricity particularly important is that it can help supply carbon-free energy for other activities, such as driving or producing things. Thus, it plays a special role in getting to zero emissions.

Although electricity has been a part of US life only since the early 20th century, it’s become ubiquitous and cheap. Producing carbon-free electricity can happen with only a small Green Premium in the US: on average, about $18 a month per home. In countries that have fewer sources of renewable energy to generate electricity, the premium will be higher. For example, in recent decades, China has driven the price of electricity way down—but only by relying on coal-powered plants. The main reasons for a Green Premium on electricity are that fossil fuels are so cheap (thanks to government subsidies) and that alternative green sources may not be constant. Most green energy relies on natural phenomena like sun and wind, and their ability to produce energy varies depending on the seasons and whether it’s night or day.