Despite recent advancements in photonics and electronics, there remains a lack of efficient, compact, high-power sources in the terahertz spectrum (0.3-10 THz). Recent research has revealed that nanoplasma (NP) switches can exhibit extremely fast transitions, on the order of picoseconds or less. However, no literature has demonstrated their ability to produce signals above 100 GHz. In this work, we present a novel technique for generating high-power THz leveraging the fast transitions in NPs. By coupling an NP switch to a judiciously designed THz resonator, we have achieved a chip-scale, high-power THz source that operates at room temperature. We report state-of-the-art peak power of 2W at 0.4 THz. While this finding highlights the rapid-transition capability of NP, it merely represents a lower limit on the NP transition speed. This research opens a pathway for efficient, compact, and high-power THz sources.