Yes, but RTGs are not particularly efficient, so much of the energy is heat. From wikipedia (https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generato

Yes, but RTGs are not particularly efficient, so much of the energy is heat. From wikipedia (https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator#Efficiency https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...): efficiencies above 10% have never been achieved and most RTGs have efficiencies between 3–7%