There seems to be several levels of compatibility, at least here in the UK, based on age.
My home is 1930s, it's fuse, in the black Bakelite housing typical of the era was insufficient and we were missing a incoming breaker to/from grid, those were updated. Our meter is much more recent, though still dated; allegedly it would have worked but it wasn't a smart meter, which we wanted so we had that updated.
I've also heard through my many hours of watching Solar videos on YT before our install that some breakers, RCDs(?), RCBOs(?), whichever it is, aren't always suitable for bidirectional current flow, so that's a possible issue too.
All of that is aside the "suicide cord" danger of the old generator method, but that's gone now with modern tech, the output is cut before you can get your hands on the contacts on the end of a plug.
It's just been legalised here in the UK, and I think it will help people with their bills, but the key is to keep installation costs down; if it's DIY you can look at a decent ROI time, but with the cost of trades-people these days, if you have to call out a sparky to inspect before you plug it in, you've added potentially years to your payback period.
At ~800W, I think on the whole we'll be fine; the equipment in our homes has got much more efficient over the years, and our homes were mostly built for times where we were using higher powered devices. If you can draw over a kW to power an electric heater or kettle, I don't see why feeding a mere 800W back in would be a huge risk.
Disclaimer: I'm not an Electrician, but I do have a degree in Electronic Engineering.