Option A) In a lot of places, you're still connected in the grid. For the sake of argument let's say, you produce 5 Kilowatt-hour in the day, and only used 2 kW

Option A) In a lot of places, you're still connected in the grid. For the sake of argument let's say, you produce 5 Kilowatt-hour in the day, and only used 2 kWh. The other 3 kWh are sold to the grid in a positive balance for you. So at the end of the month, the bill is: What you consumed to the grid in the night - what you added in the day, so depending on the sunlight you got, there could be months where you pay 0 in electricity bills. Option B) A lot of 18650 batteries and a inverter connected to your home, like the tesla powerwall.