I recently got a couple of estimates for getting solar panels installed on our roof. (I am in Southern California.)
The first installer recommended that we get 8kW of solar, and he said it would be no problem to install.
The second installer said that the maximum amount of solar we could get is 4kW. He said that if we wanted more than 4kW of solar, this would require upgrading the wires from our house to the electric company (from 100 Amp to 200 Amp) and that doing so would be expensive and would require digging up the street to lay the new wires.
Any idea what the second installer is talking about? I don't understand why that would be needed, because if electricity is flowing from the power company to us, the amperage shouldn't be any more than it is currently. And if electricity is flowing from us to the power company, the amperage shouldn't be more than 33.3 Amps. (8kW at 240V.)
Our utility is Southern California Edison. (I called them to ask about this, but they said they know nothing about solar, and that we should consult with the installer.)
Both installers said that the breaker panel would need to be upgraded from 100A to 200A. But only the second installer said that we would need to upgrade the connection to the utility (and thus dig up the street). The first installer made it sound like our panel could have 200A internal capacity, and still just have a 100A connection to the utility.
Here is a picture of our panel. (The breaker labeled "SPA" is actually the air conditioner. The previous owners had a spa, but they removed it. This breaker was unused, so when we had central air conditioning installed, we used the breaker for the air conditioning instead.)
Here is the label on the inside of the cover of the breaker panel: