He doesn't have to provide the peak energy usage. Trin, you do because you're trying to use that system to live off the grid, with your propane generator only as backup.

All he has to do is generate enough over an average 24 hour period to equal his average consumption, and he can feed to the grid and draw it back when needed.

That may not be true forever though if power companies go to hourly pricing. But that could even work out in his favor, as peak hours tend to be in daytime, so he might even be feeding the grid at peak prices and drawing, at night, at offpeak (lower) prices.