Storage Attachment Becoming the Default in Solar Projects
Not long ago, putting batteries on a solar project felt like an upgrade, the kind of thing you added if the customer asked and the budget allowed. This year it has started to feel more like standard equipment. Tax policy, utility rates, and a strained grid are all pushing the same way, and developers have noticed.
The shift is real, though it isn't happening evenly. Residential and utility-scale projects have largely made the move, while commercial and industrial storage is catching up. What follows is where the numbers stand, what is behind the change, and what it means for the people who design and build these projects.
Where the numbers stand:
Storage is already the norm in some corners of the market and a fast follower in others. On the residential side, the national solar plus storage attachment rate hit 45% in the first quarter of 2026, up from 38% a year earlier, according to ACP and Wood Mackenzie.
The bigger picture points in the same direction. Across all segments, the U.S. installed a record 18.9 GW of battery storage in 2025, a 52% jump over 2024. On the utility side, the EIA expects solar and storage to make up 79% of the 86 GW of new capacity planned for 2026.
Commercial, industrial, and community storage are the segments to watch. C&I installed 97.7 MW in the first quarter, up 27% from the prior quarter and 193% from a year earlier, though California alone accounted for 75 MW. An earlier Wood Mackenzie analysis found that non-residential attachment (the share of solar projects installed with batteries) had grown just two percentage points since 2019, so for C&I, "default" describes where things are heading, not where they are today.
What is driving the shift:
The strongest driver is a tax code that now treats solar and storage very differently. Solar projects that began construction after July 4, 2026 must be placed in service by Dec. 31, 2027 to earn the 48E credit. That accelerated deadline does not apply to energy storage, including storage at a solar site, which stays under the general phaseout that doesn't begin until after 2032 at the earliest. Capital has taken the hint. In a Crux survey, 32% of market participants said they were shifting toward storage to access the ITC, and transferable credits tied to solar plus storage projects more than doubled their market share year over year.
Rates and the grid are doing their part too. In California, the move to net billing has pushed attachment rates up sharply. For large commercial users, roughly 36 utilities have adopted large load tariffs that raise demand charge exposure for facilities above 25 MW, which makes peak shaving more valuable. Meanwhile, SEIA says permitting and interconnection delays are holding U.S. solar growth to around 44 GW a year, and it names data center moratoriums as a swing factor.
What it changes for project teams:
When storage becomes the default, supply chain, safety, and site planning all move into the base design. Battery projects must source 55% of costs from non-prohibited foreign entity suppliers in 2026, rising 5 points a year to 75% in 2030, and Wood Mackenzie notes that near-term utility-scale growth is constrained by limited availability of compliant battery systems.
Fire safety is changing too. The 2026 edition of NFPA 855 makes Hazard Mitigation Analysis a default requirement and adds large-scale fire testing provisions, which will affect design and permitting. Adoption varies by location, and some jurisdictions. Note: that the fire code they follow does not yet reference the 2026 edition. On-site, batteries bring equipment pads, clearances, and access requirements into the layout. Coordinating storage, structural, and racking design early is quickly becoming part of the basic project plan rather than a late change order.
What to watch for next:
Storage isn't replacing solar. It is changing what a complete solar project looks like.
A few things are worth watching from here.
First, whether commercial attachment rates move beyond California and a handful of other markets, because that is the real test of "default."
Battery supply is the second: as domestic cell manufacturing scales, compliant supply should ease, according to Wood Mackenzie.
Third is how quickly local fire officials adopt the 2026 NFPA 855 edition, which will shape permitting timelines. Treasury is also still working out how sourcing percentages are calculated, and that will matter for owners claiming the credit.
For owners, EPCs, and suppliers, the practical advice is to plan for storage at the first design meeting. Odds are the project will be asked to carry one before it is done.
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