A detailed investigation of the power properties of single InP/InGaAs heterojunction bipolar transistors (SHBT) is presented. High power levels of 2.74 W/mm and high power added efficiencies of 43% are also demonstrated. These properties, combined with the high frequency potential of SHBTs, make them interesting candidates for monolithic microwave integrated circuits and optoelectronic integrated circuits where the diodes can easily be integrated due to their design compatibility with the SHBT layer structure.