I have a large home, but with careful energy auditing (lower power computer, TV, all LED bulbs, etc.) I've gotten my energy usage down to about 1500 kWh per month on average. My local utility doesn't provide any rebates, tax breaks, incentives, etc., so I'd get the 30% federal credit and if I wanted to do net metering, they're paying half what they charge for electricity. Anyway - I've wondered about installed a solar array large enough to go off-grid. Something around 12-13 kW solar should do it. But, we'd need a battery system for night time use. Given we use 1500 kwH/month, that's 50 kWh per day. So the 7 kWh Tesla Powerwall would only provide, at best, 5 hours of power. It seems that I'd really want 3 times that much battery if I wanted to go off-grid. Am I doing that math correctly? Maybe more to account for cloudy days, bad weather, etc. If I am thinking about this correctly it would never make sense for me to go off-grid. Thanks for your thoughts.