On the other hand, if it's cloudy for a spell, then you'll need the grid to recharge the battery.
And then there's the question of how your bank account gets recharged (for the cost of the battery plus the solar cells, windmills, etc., plus whatever the grid charges).
It would be neat to cut the grid off altogether. But, at present, that's still way too big a hit on the bank account.
I’m charging each 470 amp-hours worth of Crown battery (about $400 for that much battery) with 280 watts of Kyocera module (nominal, about $550) before noon each day during most days. Granted, this is a sunnier area than most, and the charge controller is one of the best (about $300 worth of Midnite solar controller for the aforementioned clump of batteries and modules). Cabling, switches, etc., about $200 for that much system. Great inverter for that amount of system for a cabin or RV, about $600.
In many areas of the eastern states (say, 150 sun days), the number of modules would be doubled. Other areas, yet (75 sun days), tripled.
That’s not the size of my system, though. The figures above were only a modular chunk for rough estimates by anyone interested.
A good home inverter for a system about four times that size would run about four times as much (good system where water well pumping power is in a separate unit—generator, separate, small PV solar slow pump with cistern, etc.) and cost roughly $60 per month for replacing batteries and other components in time later on (not a bad electric bill).
But that’s for a self-install. The costs of a professionally installed and maintained system are outrageous. Technically inclined, properly licensed servants don’t come cheap.
The size of the system depends on what a family wants to run. Some folks might not be able to survive without an electric clothes dryer, for example, or an electric range (needing much more PV solar system). Some people don’t want to strain the muscles between their ears enough to build a good heating system without a forced air furnace. Some people can live large with an off-grid PV solar system. Others can’t stand it.
It’s all complicated, you know. ;-)