[hedora]

At least for our install, we spent about half the money on batteries and half on solar. It fairly reliably gets through the night unless we run the AC (but those are sunny days) or charge the car (car batteries are about the same size as the house batteries).

On a cloudy day, the panels provide 90% of our normal power usage. Anyway, to scale it up, we'd want to increase panels and also batteries. Increasing only one would leave us with no power at dawn or with a large battery that would never reach 100% in winter. One night of batteries with panels that reliably provide enough electricity to get the batteries to 100% is a good tradeoff for sunny climates. As it gets cloudier, batteries might have more incremental benefit, but multi-day storage probably doesn't make sense.

Also, you can tie a gas/propane generator to the battery to handle the "a few times a year" cases. That's probably less carbon intensive than 5x-ing the system for 1% of the days.

(Since the 1% days for us are in winter, we have a wood stove.)