Haw. Rev. Stat. § 269-105: Calculation.

The net energy metering calculation shall be made by measuring the difference between the electricity supplied to the eligible customer-generator and:

(1) The electricity generated by the eligible customer-generator and fed back to the electric grid over a monthly billing period; and

(2) Any unused credits for excess electricity from the eligible customer-generator carried over from previous months since the last twelve-month reconciliation period.