Bob would like to run his house off the grid, therefore he needs to find out how many solar panels and batteries he needs to buy.
The power output of a 250 W solar panel is p=250−10(t−5)2 watts for the average 10 hour day. He plans on using 12 V, 120 A⋅h batteries and would like to able to store 3 days worth of energy. Bob's house uses 1100 kW⋅h per month (30 days).