Realistically 25-30A with thick copper wire are doable. 20V is a good ground but even then it could power a TV + couple laptops, perhaps lights too. That would be a solution to have dedicate DC lane in-house but the conversion to low voltage DC must have in-house (office buildings would require tons of copper). Galvanic corrosion might be an issue to a certain degree.

Carrying high voltage DC, comes with its own issues - likely doable though. Many household devices would run perfectly fine on high voltage DC (instead of AC).