What cost?  It sounds like the parent is possibly suggesting the opposite of a backup power solution: transfer switch where you&#x27;re in solar mode 99% of the time, and if things break or you need to do work, you switch over to grid power.<p>I&#x27;ve never lived anywhere where I used zero kWh for the month, so I&#x27;m not sure... but I have to imagine the cost would be pretty slow... save for getting such a system setup (transfer switches are common enough with backup generator situations so I can&#x27;t imagine that portion would be very expensive)