Haw. Rev. Stat. § 269-108: Net electricity producers; excess electricity credits and credit carry over.

At the end of each monthly billing period, where the electricity generated by the eligible customer-generator during the month exceeds the electricity supplied by the electric utility during that same period, the eligible customer-generator is a net electricity producer and the electric utility shall retain any excess kilowatt-hours generated during the prior monthly billing period; provided that the excess electricity generated by the customer-generator, if any, in each monthly billing period shall be carried over to the next month as a monetary value to the credit of the eligible customer-generator, which credit may accumulate and be used to offset the compensation owed the electric utility for the eligible customer-generator's net kilowatt-hour consumption for succeeding months within each twelve-month period; provided further that the electric utility shall reconcile the eligible customer-generator's electricity production and consumption for each twelve-month period as set forth in section 269-106. The eligible customer-generator shall not be owed any compensation for excess kilowatt-hours unless the electric utility enters into a purchase agreement with the eligible customer-generator for those excess kilowatt-hours.