DARPA and NASA have some combined projects developing small reactors suitable for both mars and deep space exploration as well as replacing oil tanks for generators in remote military installations like in the arctic. This is almost certainly chasing that, not consumer generation.
The Curiosity and Perseverance rovers each carry an old kind of power supply: a nuclear power generator that runs on radioactive plutonium dioxide.
This generator has been used on many missions since the 1960s.
It produces a steady 110 watts of electricity. The decay of the radioactive material also emits heat, which helps keep the electronics onboard warm through the freezing nights on Mars.
Supplemented by rechargeable batteries, the generator provides enough power to let the rover pull all-nighters for years to come.
RTGs are horrifically inefficient sources of power. They work well enough for providing a paltry 110W to a rover on another planet, but that's not going to scale up to providing power for millions of people. The amount of plutonium you'd need would be astronomical.
