alt Hacker News> if you owned a battery that charged off the grid and discharged during blackout periods
This wouldn't work. The reason isolated units can inject electricity back into the grid without issue is that they can observe frequency. If a blackout occurs, this information is gone. You need to perform a black start, which can't be done by isolated, uncoordinated equipments.
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Pretty sure GP was talking about a UPS, not feeding the grid.
I don't think that applies for microgrids, or at least, it's not really an issue in my case.
I know what you're talking about though: I think that more applies to generators that are operating with megawatts and take time for turbines to spin up and stuff. Microgrids are normally instantaneous battery buffered type things. They can instantly deliver power at the frequency range mandated for the national grid.
What you actually need is islanding equipment which discharges the battery for local use only, but cuts off (or islands you from) your main incoming power connection.
Many of the PV systems you can buy from the big players (SolarEdge, Tesla and more) support this, often calling it "whole home backup".
Same principle as having a generator with an interlock.