Buildings in Rizhao, a coastal city of nearly three million on the Shandong Peninsula in northern China, have a common yet unique appearance: most rooftops and walls are covered with small panels. They are solar heat collectors.

A combination of regulations and public education spurred the broad adoption of solar heaters. The city mandates all new buildings to incorporate solar panels, and it oversees the construction process to ensure proper installation. To raise awareness, the city held open seminars and ran public advertising on television.