In Kauai island of Hawaii, AES is installing 28 MW of solar PV with 20 MW/100 MWh of battery for $0.11/kWh. In 2015, 13 MW solar PV with 52 MWh battery from SolarCity was signed for $0.145/kWh. With significant storage, this was billed the "first fully dispatchable solar plant."
Currently the island is powered by diesel and the generation cost is 0.15+ per kWh. The average residential tariff is $0.323/kWh. And no discussion is complete without the beautiful duck curve:
If KIUC could move some of it solar generation to later hours, it could decrease its reliance on dirty fuel oil, prevent solar curtailment at midday, and save customers money.
redit: DOE solar DG presentation
For more details see http://www.utilitydive.com/news/hawaii-co-op-signs-deal-for-solarstorage...