Examples of heat exchanger systems for active radiative cooling are described. In one example, the system includes a heat exchanger and a spectrally selective surface material on at least one surface of the heat exchanger. The spectrally selective surface material exhibits high reflectivity at shorter wavelengths and high emissivity at longer wavelengths. The system can also include an active cooling system in some cases to actively transfer heat to the heat exchanger. The use of spectrally selective surfaces that operate at temperatures exceeding that of the outdoor ambient for which convective losses augment radiation losses have advantages over passive cooling, such as but not limited to: providing a better match to cooling loads, reducing the heat rejection surface area required to achieve a desired cooling rate, and increasing the heat transferred to deep space through the atmospheric window so as to simultaneously cool infrastructure, devices, buildings, and Earth.