Microwaves (MWs) are at the heart of many technologies, $e.g.$ for communication, timekeeping, remote sensing, and quantum information processing. Masers can boost faint MW signals quite nicely, but not under real-world conditions. The authors demonstrate efficient population inversion of optically pumped vacancy-related spins in SiC, at room temperature, and find realistic operating conditions for a SiC maser to serve as a continuous-wave amplifier. These spins can also be coherently coupled to superconducting cavities efficiently at cryogenic temperatures. These findings suggest this SiC system as a promising platform for MW photonics and quantum electronics.