90% of that would be lowering the total energy costs of the structure.
Figuring out magic ways to live well off the grid involves being more efficient first.
For example, my house (built in 1979) is so efficient that my total power bill is $70 a month (and the price per kwh has increased 50% the last few years). Grid electricity is so cheap, I couldn't afford to install something like a generator.
I have been meaning to gather up all my wall warts and measure how much standby power all my DC appliances pull. It wouldn't be difficult to convert all my phone jacks to 12V and power it with car batteries in my tool room (that I have on charge anyway) and run them off a harbor freight solar panel.
With the exception of the panel, it would pretty much be free to do. But at only 3 or 4 dollars a month, the breakeven point would be decades down the line.