A system and method are disclosed for internally heated concentrated solar power (CSP) thermal absorbers. The system and method involve an energy-generating device having at least one heating unit. At least one heating unit preheats the energy-generating device in order to expedite the startup time of the energy-generating device, thereby allowing for an increase in efficiency for the production of energy. In some embodiments, the energy-generating device is a CSP thermal absorber. The CSP thermal absorber comprises a housing, a thermal barrier, a light-transparent reservoir containing a liquid alkali metal, at least one alkali metal thermal-to-electric converter (AMTEC) cell, an artery return channel, and at least one heating unit. Each heating unit comprises a heating device and a metal fin. The metal fin is submerged into the liquid alkali metal, thereby allowing the heating device to heat the liquid alkali metal via the fin.