The setups have to be separate (e.g. different outlets for mains and solar) to protect the grid.
Even a small home solar installation puts out enough power to easily kill unsuspecting maintenance personell working on the grid, for example.
So the utility company has to have 100% control over he mains at all time for safety reasons (i.e. your meter must never run backwards). If they cut the power (e.g. for maintenance or repairs), no one must be able to feed power into the grid.
That's why even if you have a battery, said battery can either feed into the grid, or be connected to separate outlets in your house, but never both at the same time.
> So the utility company has to have 100% control over he mains at all time for safety reasons
This is controlled independently by the solar inverters's software, not the utility via any sort of signal. That software is mandated by regulation as you say for the safety of line workers. Recent batteries allow for an "islanding" mode, which allows continued backup power delivery to the house during a grid outage but cuts off the grid connection.
> your meter must never run backwards
... during a grid outage. During normal operation it's fine for it to run backwards. That's what net metering quantifies.
> said battery can either feed into the grid, or be connected to separate outlets in your house, but never both at the same time.
I think this is a technical limitation, since it would require a current divider and 2 inverters, which is a level of complexity not worth it for the application.
That's not true, you can have an inverter setup which fails over to a battery backup when the grid goes down. It's also done all the time with natural gas generators.
The setup is more expensive, and it does have to meet certain requirements, but it is definitely an option.
Meters run backward intentionally when selling solar back to the utility. You need a switching system that will isolate immediately if the grid fails, and resync with the grid AC before reconnecting, if you want to be able to operate on and off the grid.
Even a small home solar installation puts out enough power to easily kill unsuspecting maintenance personell working on the grid, for example.
So the utility company has to have 100% control over he mains at all time for safety reasons (i.e. your meter must never run backwards). If they cut the power (e.g. for maintenance or repairs), no one must be able to feed power into the grid.
That's why even if you have a battery, said battery can either feed into the grid, or be connected to separate outlets in your house, but never both at the same time.