Hereis a post from Alt tech site
Here is an attempt at the whole house off-grid needs.
My usage has traditionally run at about 1200kwh per month.
Thats about 40 kwh per day.
To cover this usage, I would need to consider roghly this:
Solar Panels / PV:
an example: 170w panels over 4 net hours of peak performance = 680 watt hours 40000/680 = 59 panels needed!
so, 60 panels at about 800$ each = 48,000$ !!!
an example: 100ah 12v = 1200 watt hours deliverable max at full discharge
To stay in the top 20% ( for longevity and give a couple of days when sun is poor ) = 1200*.2 = 240 watt hours per battery
40000/240 = 167 batteries needed !
so, 168 batteries at 200$ each = 33,000$ !!!