After reading these comments, I am even more confuse!
As a new person investing in to solar panels for my home, I would think this system should cover all my energy usage for the year base on my past 12 months of energy usage. According to Tesla, this system should generate more than enough, but yet I still have to pay for electricity?
My system is oversized, shouldn't this make up for my energy usage and some?
Even if I downsize to the 4.08 kw system, I would save about $4k and the system would generate just enough to cover my usage. It’s probably to late now to do it, but I am just trying to educate myself and learn more about solar panels.
It is not as simple as that because net metering is using $ amount at the time of generation and usage instead of kWh.
For example, using your numbers, averaging in a day, you generate 26 kWh and you used 18 kWh. Outside of non-bypassable charges, are you ahead that day? It depends on when you use the energy.
Scenario 1: 80% of usage outside of 4pm to 9pm during Summer
Generation = 26 * $0.27 = -$7.02
Usage = (80% * 18 * $0.27) + (20% * 18 * $0.43) = $5.44
In this case, you are ahead = 5.44 - 6.75 = -$1.31
Scenario 2: 30% of usage outside of 4pm to 9pm during Summer
Generation = -$7.02 (same)
Usage = (30% * 18 * $0.27) + (70% * 18 * $0.43) = $6.88
In this case, you are still ahead but barely = 6.88 - 7.02 = -$0.14
If you want to see the lowest bill possible, try to keep you 4pm-9pm usage under 70%. Definitely do not charge your car during that time if you can help it. Now you are thinking, it is really easy to keep evening usage under 70% of total usage. Yeah, because you oversized your system.
What happened if you sized it at exactly18kWh generation per day?
Scenario 1: 80% of usage outside of 4pm to 9pm during Summer
Generation = 18 * $0.27 = -$4.86
Usage = $5.44
In this case, you are behind = 5.44 -4.86 = $0.58
So even if you could keep your evening usage under 20%, you will still end up with a monthly bill of $17 + non-bypassable about $16 = $33.