The solar industry is no longer just talking about pairing energy storage with solar generation.

An increasing number of solar-plus-storage projects have been cropping up around the country, as lithium-ion prices drop lower and customers get more comfortable with storage technology. The AES plant in Kauai set a record-low price in January, only to be beaten by Tucson Electric Power's sub-4.5 cents per kilowatt-hour PPA announced in May -- proving this technology isn't just for islands and remote microgrids anymore.

For the large developers in particular, storage makes the solar product more appealing to a utility by giving the power plant flexibility and mitigating its effects on grid operations. On the islands of Hawaii, storage has already become necessary for adding major solar capacity; on the mainland, its value increases along with renewable penetration.

To get a handle on just how extensive the interest in storage-backed solar is, I got a list of the 10 largest utility-scale solar developers from my colleagues at GTM Research and tracked down the storage status of each one.

Eight* of the top 10 solar developers have incorporated storage into their business strategy, and have either deployed storage alongside PV or are pursuing hybrid installations. The remaining two did not comment on how storage fits into their plans.

"This is well beyond one developer -- this is really a trend we're seeing in the industry," said Colin Smith, a solar markets analyst at GTM Research. "Solar-plus-storage has become a forced differentiator in the industry."

First Solar: Bidding on storage

The thin-film solar specialist first invested in energy storage in 2015, when it joined a $50 million investment round in German startup Younicos. At the time, First Solar CTO Raffi Garabedian commented, "As the promise of storage continues to evolve, we are eager to understand how it will broaden our own power plant offerings.”

These days, the No. 1 U.S. solar developer routinely permits new projects in the western U.S. for the possible addition of storage, because so many customers are asking about it, said Scott Rackey, head of PV-plus-storage development at First Solar.

"It’s a small cost to gain the optionality later," Rackey said.

First Solar has been bidding on solar-plus-storage, including several projects at the scale of 100 megawatts of PV with 100 megawatts of battery capacity. The ideal ratio varies depending on the local grid, Rackey noted: the Southeast tends to have more appetite for PV generation during the day than Arizona, for instance, where oversupply of nondispatchable PV is becoming a challenge.

"It’s really become cost-effective in roughly the last year or year and a half for dispatchable PV," Rackey said. "We can deliver energy comparable to or less expensively than a new-build fossil fuel plant."

Expect some storage news from this company, then, in the months to come. First Solar, by the way, prefers the svelter acronym "PVS," rather than the cumbersome hyphenations of "solar-plus-storage."

Florida Power & Light: Systems deployed

Florida's regulated utility has three grid-scale storage systems of 250 kilowatts developed by S&C Electric, according to the GTM Research Energy Storage Data Hub. FPL also committed in its last rate case to implement a 50-megawatt battery storage pilot program available to all customer classes.

The utility also joined the Obama administration's White House energy storage summit last year, pledging several demo projects: a battery backup system at the southern tip of Everglades National Park; second-life electric vehicle batteries deployed in residential parts of Miami; and "a portable system to be tested during the 2017 Miami Open at Crandon Park Tennis Center on Key Biscayne." 

These storage projects are not paired with solar, though. FPL recently launched a building spree of solar farms across the state of Florida, with eight 74.5-megawatt plants slated to open in the next year. So far, none of them appear to have storage in the mix. This utility's take on a hybrid solar plant pairs it with natural gas.

Still, the utility is building knowledge in storage deployments as it ramps up solar capacity. Those two product streams could converge in the next few years.

NextEra Energy Resources: Systems deployed

The sister company of FPL, under the parent company NextEra Energy, dominates in both renewable generation and the storage industry.

The company ranks second in terms of actively deployed and under-contract storage capacity, with 76.4 megawatts of grid-scale storage operational, according to GTM Research. It was NextEra that signed the PPA with Tucson Electric Power for the record-setting solar-plus-storage project in May. That one pairs 100 megawatts of solar PV with a 30-megawatt/120-megawatt-hour storage system.

Storage has become a thriving part of the overall company, Senior Vice President of Development Michael O'Sullivan said at the Energy Storage Association conference in Denver back in April. Whereas it was hard to find staff to bet their careers on wind and solar in the early days of those industries, the best and brightest from a whole range of age groups are asking to work on energy storage.

“The human capital…want to be in this sector and want to make a difference,” O'Sullivan said. “As long as that continues, that’s a great indicator, just as the opposite is true.”

SunPower: Systems deployed

[Update 6/15: SunPower contacted GTM to note the company has developed solar-plus-storage at the commercial scale for customers like Target and Macy's.]

The company's stance on utility-scale storage remains unknown, but SunPower has been thinking about energy storage for some time at the smaller scale.

A residential partnership with storage-maker Sunverge dates back to the end of 2014, making SunPower a pretty early adopter. A commercial storage partnership with Stem followed soon after.

Cypress Creek Renewables: Deploying storage

Santa Monica-based Cypress Creek is preparing to deploy its first 6 megawatts of energy storage later this year for a municipal utility in North Carolina. The company has up to 50 megawatts of additional energy storage deployments also in the works.

Moving into storage isn't a choice for solar developers; "It's a self-preservation question,” CEO Matt McGovern told GTM's Julia Pyper.

“If we sit back as an industry, and we say, ‘No, it's up to the utilities, or it's up to the grid operators,’ we're not going to like" the outcome, McGovern said. "I think the opportunity is for us to be thinking a little ahead, understand the pain of the utilities, and actually come forward with solutions.”

NRG Energy: Deploying storage

NRG will supply New York utility Consolidated Edison with two mobile batteries totaling 1 megawatt/4 megawatt-hours, expected out this quarter. The mobile units will be able to move to wherever they're needed most to help with grid congestion.

The company has worked with storage in small-scale applications, but has not committed to it as a fully fledged competitor to conventional gas plants, as some energy storage developers have. The California Energy Commission this week ordered a study of whether energy storage or other resources could meet the needs of the Oxnard grid in place of a gas plant to be built by NRG. An NRG spokesperson responded that "no additional feasible, cost-effective and available preferred resources have been identified that would eliminate the need for the Puente Power Project," The L.A. Times reported.

NRG will also work with Ice Energy to develop up to 1,800 behind-the-meter ice batteries as part of a contract with Southern California Edison. That distributed fleet will provide an aggregated 25.6 megawatts of peak storage capacity for the utility, comparable to a large utility-scale system by today's standards.

These storage projects are happening independent of NRG's solar development so far.

Recurrent Energy: ???

A representative for the San Francisco-based subsidiary of Canadian Solar said, "At this time, we are unable to participate" in an interview about energy storage. Depending on how you read "at this time," that could mean some storage announcements are working their way to fruition.

SPower: Pursuing storage

Storage has been on sPower's radar since the company got started, said CEO Ryan Creamer.

"We designed facilities to be able to go back in and add storage when it became economical," Creamer added.

The company hasn't deployed storage yet, but it has "a couple of things in the hopper," Creamer noted. Notably for its storage ambitions, sPower is undergoing an $853 million acquisition by AES, which happens to run one of the most prolific storage development teams in the country. That opens up some opportunities for collaboration, once the acquisition is finalized.

"Hopefully, there are some synergies we pick up from being one and the same family," Creamer said.

Sempra Generation: ???

Sempra's subsidiary San Diego Gas & Electric ranks as the No. 3 owner of storage assets, with 41.9 megawatts, much of that spurred by the Aliso Canyon procurements. The parent company, though, doesn't list energy storage on its roster of energy assets, which includes wind farms, solar plants, hydropower and gas infrastructure. A spokesperson declined to elaborate on the company's plans for energy storage.

8minutenergy: Bidding on storage

This company spent the past year building up a storage team, and unstealthed it in May with a 1-gigawatt pipeline across the Southwest, ERCOT territory and the Southeast. 8minutenergy now routinely factors storage needs into the design of its new projects, as I reported here.

Its strategy is to work with utilities to develop large-scale projects, on the order of 100 megawatts of solar and of storage. The hybrid plants will deliver dispatchable power that is protected from future curtailments, and make better use of the transmission lines utilities build to remote solar farms.

*Updated to reflect new information that SunPower provided after the article's publication.