When the Tesla Gateway detects the grid is down, excess solar power is used only to charge the PowerWalls. And when the PowerWalls get near to full, the Gateway changes the power frequency above 60Hz, which causes the solar power inverters to shut off, so no power from the solar panels will even be sent into the Gateway.
During an outage - no power is sent to the grid.
We live in the Houston area. Generators will usually run off the same gas lines that go into the houses for use in appliances and HVAC systems.
We have the only solar panels on our street. Two houses next to us have gas generators. When we lost power, we switched over to our PowerWalls - and for those houses, their generators kicked on - and you can definitely hear them running.
As far as I know, our area did not have any problems with natural gas lines.
Our concern was that when our power went out, the "authorities" were indicating new outages could last days - and with the prospect of little sun for the next day, we took steps to drastically reduce consumption, just in case we needed to run off the PowerWalls for more than 24 hours. Our neighbors with the generators were fine and only had to worry if the natural gas lines went down - which haven't happened as long as I can remember in our area - even after hurricanes, the natural gas lines have worked.
Question: Does your neighborhood allow large propane tanks using underground lines to supply the generator/house?