Comment by nuccy

The heat is dissipated by radiation, that's why apart of solar panels all sattelites and space stations also have radiators for thermal management. The average space temperature (far away from stars) is 2.7K (the temperature of cosmic microwave background, CMB), so going below that is hard. Sun would heat up a bit Voyager 2 but at 143au it is just 1/143^2 fraction of solar power on Earth orbit, thus 0.0049%, or just 0.067W/m^2, so extra power is needed to maintain electronics operational.