A passive temperature regulator

\nMaintaining stable temperatures is crucial for civilization, but it typically requires substantial energy consumption, contributing to significant carbon footprints. Despite advancements in passive heating/cooling technologies, achieving purely passive temperature regulation in volatile environments remains a challenge due to the temporal mismatch between heating/cooling demand and passive power supply. Here, we demonstrate a passive temperature regulator that balances the power demand and supply through a tailored sandwich structure, integrating the functionalities of harvesting, storage, and release of passive solar heat and space coldness. Outdoor experiments demonstrate that the regulator maintains a target temperature for 96% (71%) of the testing period in winter (summer). Compared to conventional solar absorbers (radiative coolers), the regulator saves 56% (30%) of energy across 31 cities worldwide in achieving stable temperatures. The regulator represents an important advancement in passive temperature regulation with minimized carbon footprint and shows attractive prospects both on Earth and in outer space.\n