Do I need to upgrade my main utility service panel to go solar?
Your service panel's kVA rating — calculated from its voltage and amperage — sets an upper bound on solar system size, alongside your transformer capacity.
Your main utility service panel has a maximum capacity, and your solar system can't exceed it. To figure out that limit for a three-phase panel, you need two numbers from the panel's nameplate: voltage (V) and amperage (A).
The formula is: kVA = V × A × √3 ÷ 1,000. For example, a panel rated at 2,500A and 480V gives you kVA = 2,500 × 480 × 1.732 ÷ 1,000 = 2,078 kVA. That means the maximum AC rating for your solar system is 2,078 kW-AC.
One important detail: your solar system's maximum size is limited by the lower of your service panel's kVA or your transformer's kVA. If your panel supports 2,078 kVA but your transformer is only rated for 2,000 kVA, the system caps at 2,000 kW-AC. If your desired system exceeds either limit, you'll need to upgrade the limiting component or reduce the system size. Getting both ratings documented early in the process avoids surprises later.