In only a few years, solar paired with energy storage has gone from a niche concept to the new reality of the U.S. power system. And it all really came down to price.

While the 14.5 cents per kilowatt-hour that SolarCity was able to achieve with solar plus storage on Kaua’i was groundbreaking three and half years ago when it was announced, today Hawaiian regulators set a new threshold for the price that solar projects fully backed by four-hour batteries must beat: 10 cents per kilowatt-hour.

The Hawaiian Public Utilities Commission (HPUC) has approved contracts between the subsidiary utilities of Hawaiian Electric Industries and the developers of six projects, representing a combined capacity of 247 MW of solar, and 998 megawatt-hours of energy storage – meaning that the entire capacity of all six projects will be fully backed by four-hour batteries.

The price for each of these contracts was between eight and ten cents per kilowatt-hour. This is cheaper than both gas peaker plants and HEI’s current cost of fossil fuel generation, much of which is petroleum-based, which the company put at around 15 cents per kilowatt-hour.

HPUC is holding two other contracts for further review, and earlier filings indicate that one of these was priced at 12 cents per kilowatt-hour.

Utility-scale solar output to grow more than 3x

These projects will substantially add to the utility-scale solar generation in Hawaii. Unlike all other states that pv magazine has studied, the large majority of solar that has gone online in Hawaii is rooftop solar, not large-scale.

These six projects will dramatically increase the volume of utility-scale solar on the island chain, and using 2017 capacity factors provided by the U.S. Department of Energy, pv magazine estimates that these will generate somewhere in the neighborhood of 480 gigawatt-hours of electricity annually, more than tripling the current output of utility-scale solar as the island moves towards its mandate to get all of its electricity from renewable energy sources by 2045.

But perhaps more important than that is that these projects can be used to supply electricity during the evening peak and on cloudy days, moving solar from an intermittent, mid-day supply of electricity to a dispatchable resource.

As such, they are ushering in the age of the solar peaker. And there will be more where these came from.