What is a "solar ready" electrical panel and how does it save money in a solar installation?
“Solar Ready” devices route the alternate power to the supply side of
the service disconnecting means and provide terminations to the load
side of the meter socket. This eliminates having a common bus and
therefore the need to de-rate the main breaker.
https://www.downloads.siemens.com/download-center/d/SIE_BR_SolarSolutions.pdf