I understand that solar panels are rated for a certain wattage but that that is the theoretical maximum power output of the panel. How do I calculate the actual amount of energy that I will get from a panel or array based on this rated wattage and factors such as hours of sun light, direction...

I have heard there will be federal tax credits for battery storage. When do tax credits become available for installing battery storage? Are there other incentives than federal tax credits in California? If so, what what do I have to do to qualify?

How do I calculate how much energy storage I need for my house to be mostly self sufficient with the grid as backup?