The Rusk's own fairly large house near San Francisco and the following spreadsheet shows their month to month power use for two years. 

1. What is their monthly average power use? 

Extra point: Why do you think their use peaks twice a year?   

2. Calculate the size of the solar PV system (kWh DC STC) they will need in order to  have a zero dollar electricity bill annually (use an average over the two years).   Assume that you are using 14.9% efficient panels with an 80% derating factor.  Also assume that your inverter is 95% efficient.  Use an average solar insolation of 5.5kW/day for their location.   

3. Assume this system will be mounted on the roof.  How big will the area of solar collector be?   Is this a reasonable size for a house (i.e. are roofs actually this big)?     

4. What is the AC, PTC per square meter for the system?  Assume that the 80% derating factor gets you from DC, STC to DC, PTC.