Most cities require a grid electrical connection as a requirement for habitability. The codes all refer to ‘utility providers’ for building permits, and require utilities (including electrical, water, etc.) be present and provided before the unit is considered ‘habitable’. Even temporary power (required to start construction before you could even install a solar installation, with the way most permits are done) has to be permitted and done a specific way.
At a state level they’ve been making it clearer that it is technically legal - but it’s still hard to actually do.
There has been a lot of controversy on this topic, with permits getting denied in cities when the plan was to be off grid (and people just caving), and some utilities explicitly raising connection fees to ensure zero-usage customers were still paying them.
It gets people really angry too of course (at least in the US) because ‘what do you mean big government won’t let me do what I want on my own land!’.
The reality is, the types of folks who actually want to go truly off grid (and don’t feel the need/prioritize the backups provided by an optional grid connection, or think it is too expensive) probably already live far enough in the boonies that building codes are largely optional anyway.
It’s pretty rare that a random city dweller is going to be trying to go 100% off grid in their condo, or would have the physical space or legal ability to do so, regardless of what the city says.
And code enforcement looking too closely at things way out in the sticks tends to find itself in some very dangerous situations - the type people just disappear from sometimes and are never found - especially out in the remote parts of America’s deserts/woods.
