Different electrical and thermoelectric properties of a Si-based thermoelectric generator (TEG) are described based on the Kubo–Greenwood formalism. Temperature and doping dependence, phonon scattering (acoustic and optical phonons), and scattering on impurities are included. Comparisons with experimentally verified data confirm the validity of the model. Experimental studies were carried out on a micromechanically fabricated TEG. Devices were realized using a standard CMOS SOI technology in a lateral geometry. All thermopiles are located on a thin membrane to reduce the heat flow. The thickness of the membrane was adjusted between 20 and 30 µm ensuring also sufficient mechanical stability. Measurements on individual devices confirm the results of the theoretical model. The Seebeck coefficient was calculated and experimentally measured as S = 0.5 mV/K at an acceptor level of 1019 cm?3 at room temperature. The power factor is S2?·?? = 0.0073 W/mK2.