SREC auctions in Delaware have been closing at a price of $300. This is higher than Delaware’s solar ACP, which begins at $250 per MWh. This discrepancy is caused by increases in the penalty for electricity suppliers after the first time they fall short of their solar requirement. The solar ACP increases to $300 after the first time an electricity supplier falls short, and then increases to $350 for any subsequent penalties.
So in summary, the reason you might see prices higher than $250 is because buyers are forced to pay a higher fine if they have previously fallen short on their requirement.