Solar + a battery system is the best option, Having power during an outage is a huge benefit and I'm sure would sound perfect when trying to sell the propriety. Also, many people don't know this but charging an EV from batteries is many times better then stepping grid power upwards.
It is only 2 months of stats for me. I've started topic here for that: http://www.geekzone.co.nz/forums.asp?forumId=141&topicId=199024
Or direct link to the monthly stats I am publishing about my system (3KW + Tesla Battery) is here: https://www.facebook.com/toyotahybridbatteryexperts
In my special case with Vector the sytem is not set up with a back up option although potentially is capable of that, hence I had to come up with my own solution for the outages which is "deep cycle batteries" (another 6KWH, not Tesla).
If one has a Prius - then it is a "generator on wheels" so you do not need another back-up generator.
As for "charging EV from batteries" - does not sound right unless you've made a typo.. Please explain which EV and what batteries are you talking about and what type of charger are you going to use to charge those batteries in the first place to make it "many times better"?