ProVision Solar has completed the installation of a 105-kilowatt solar electricity generating system on the roof of Molokai General Hospital, the largest such system on the island.

The system’s 315 photovoltaic panels will produce about 25 percent of the hospital’s power needs, or an estimated 170,000 kilowatt-hours of electricity in its first year of operation, according to Hilo-based ProVision Solar.

Molokai General Hospital in Kaunakakai signed a power purchase agreement with California-based Solar Power Partners, which will operate the PV system and sell power back to the hospital at a fixed rate over the life of the contract. The price tag for the project and terms of the power purchase agreement were not disclosed. However, under most power purchase agreements, the customer buys the electricity from the system operator at a rate less than what the customer would pay to its local utility.

With the addition of Molokai General, alternative energy generation now makes up more than 15 percent of peak load in both Kaunakakai and the Hoolehua-Kalae area of Molokai, according to Maui Electric Co. And 15 percent is the "feeder penetration limit" set by the Public Utilities Commission.

Under a PUC rule, any home or business seeking to install a new PV or other alternative energy generation system after the area has reached 15 percent penetration must first conduct an "interconnection study" to determine whether that system might adversely affect other customers on the circuit.

The cost of such studies can range from $15,000 for a single-family home to $40,000 or more for a commercial power customer, according to several local PV system installers.