Competition in stationary storage is "bench-deep" and aggressive.
"the cooperative utility announced a
groundbreaking deal with SolarCity in September 2015 for a solar plant backed by batteries. That project,
still under construction, paired 17 megawatts of solar PV with Tesla Powerpack batteries with 13 megawatts of power and 52 megawatt-hours of energy. The price tag on that power:
13.9 cents per kilowatt-hour...
The project ... will combine 28 megawatts of solar photovoltaic capacity with 20 megawatts of five-hour duration batteries. AES will own and operate the system, and has executed a power purchase agreement to sell power to the Kauai Island Utility Cooperative (KIUC) at 11 cents per kilowatt-hour. The project is expected to be operational by late 2018...
In a little over a year, then, solar-plus-storage economics have improved such that AES can field more power capacity, an additional hour of duration and a lower volumetric price than SolarCity's project.
AES’ New Kauai Solar-Storage ‘Peaker’ Shows How Fast Battery Costs Are Falling
Summary:
17 MW of PV vs. 28 MW
13 MW of power vs. 20 MW
$0.139/kwh vs. $0.11/kwh
One extra hour on the batteries (when da sun don't shine).