I'd happily have a RITEG buried in my back yard to sustain my base load from my house. Using geothermal cooling for the unit seems like a good idea, and it would be underground where nobody can fuck with it.

RITEG research and use hasn't stopped, but most of the terrestrial units have been long decommissioned. The most recent example of note was the MMRTG unit used in curiosity (now on Mars), which is 45 KG and can produce 110W of output. The most notable terrestrial examples were the IEU units used by the Soviets for light houses, weighing upwards of 2-3 tones and producing less than 120W at their peak, mostly fueled by strontium 90 (the MMRTG uses plutonium 238). The only modern RTG for terrestrial use is the Sentinel units used for monitoring stations in the arctic by America, which top out under 60W and weigh more than a ton, closer to 2 ton. There are others but information is limited.

A lot of weight is due to the fuel (which is classified as a "heavy metal") and the casing, which on earth is more robust than you would need in space, since it's feasible that people would be nearby the unit for extended periods of time and any breach could be fatal.

Even with the weight, if we're effectively burying it in a yard, deep enough to take advantage of geothermal cooling, then weight isn't really a problem. Even size isn't a problem since it can be the size of a large consumer vehicle and most homeowners have more than enough land to accommodate that... With little more than an access hatch for inspections and maintenance, it would be a viable option to contribute to offsetting the base load of your home. Even a 100W unit would trim about 2.4kWh from a household electricity bill per day for something like 100 years. That's in the ballpark of 8.5 GWh over the lifetime of the unit before the fuel needs to be replaced (based on the half life of the material. Strontium 90 would need to be refueled every 40-50 years or so).

I'm not saying it's a fix to the problem by any stretch, but it could trim about 1/4 of electricity costs per home, based on an average consumption of around 10 kWh per day.

This is why I like RTGs, they're stable and long lasting, relatively safe (unless the housing/shielding fails) and solid state with basically no maintenance.

I'm a fan of the idea, but I'm not going to say it's a one stop fix, nor do I think the regulatory people will green light any implementation of such a system for home use, ever. Nor do I think that even if such a solution were to be given approval, that the general public would ever accept it being installed "in [their] back yard" either literally or figuratively.

You're right that a pair of 200W panels and a small battery system would have a similar effect (at least until the batteries needed replacing... or simply grid tie it), and as long as you can average ~2 kWh/day of generation, you'd be fine... You might need 4-5 panels to get the same daily output, but a system like that is probably still less than $1000, and will probably last ~20 years. So to make it economically viable such a system would need to cost the consumer less than ~$5000 or so before it becomes a better option.

I'm still a fan of the technology, and I find it immensely interesting, but I try to keep my expectations realistic. Due to the excessive weight of a terrestrial RTG, it's not viable for a vehicle, but wouldn't it be cool to have a car that charges itself all the time no matter where you park it or whether it's in the sun or not?

I think that would be cool.