CMS Opens a Federal Path for Battery-Backed Hospital Power, While Codes and Insurers Hold the Line

The Centers for Medicare and Medicaid Services has removed the requirement that a hospital maintain a fossil-fueled generator as its primary emergency power source. The Health Care Microgrid Systems categorical waiver brings CMS regulations in line with the National Electrical Code, “which permits the use of microgrids,” according to Trellis. Before the waiver, a hospital that installed solar paired with batteries still had to keep the diesel unit as the mandatory primary system. As Trellis put it: “They were not allowed to use renewable microgrid systems, for example, solar with batteries.”

That is one of several regulatory layers that moved on building-sited batteries this year. The CMS action is the only federal one. The others are private model codes, which carry no legal force until a state or local authority adopts them, and a fire-permitting regime and an insurance market that are moving in the opposite direction. The gap between them is where projects will stall.

The NFPA 110 change. The 2025 edition of NFPA 110, the standard governing emergency and standby power supply systems, expanded permitted battery chemistries for the first time in decades. GenServe, a compliance services firm tracking the cycle, said “batteries such as nickel-zinc and lithium-ion, in addition to traditional lead-acid and nickel-cadmium, are now allowed so long as they meet cranking performance criteria.”

Cranking is the engine-start function, which suggests the provision substitutes a component inside a generator set rather than authorizing a battery to carry an emergency load. That reading is worth stating explicitly, because secondary coverage of the 2025 edition has tended to present the change as a broader opening than the cranking qualifier appears to support. GenServe said the updates are being adopted into local regulations throughout 2026.

The NEC 2026 recognition. A compliance guide published by ZCC Power said the 2026 National Electrical Code “now recognizes energy storage systems (ESS) and hybrid generator-ESS systems as valid emergency power sources,” and sets “new installation standards for battery energy storage systems (BESS) which operate together with diesel generators.”

The architecture that guide describes splits the job by timescale. Batteries carry the instantaneous Type 10 transfer requirement; the generator holds Class 96 duration. That division is narrower than a diesel replacement and more durable than a pilot. It gives storage the transfer speed and leaves the endurance with the generator, which puts a battery into a capital budget line that has been diesel’s alone.

The New York City permitting path. Department of Buildings rules 101-19 and 3616-07 govern the design, filing, construction, commissioning, operation and decommissioning of energy storage systems, and 3616-07 adopts a locally modified version of NFPA 855. The modification that matters for in-building work is the threshold: DOB reduced the minimum aggregate capacity trigger in Table 1.3 to one kilowatt-hour for lithium-ion and other chemistries, far below the unmodified NFPA 855 values, in order to capture smaller systems and to align with anticipated Fire Code changes. Every indoor energy storage system must be inspected and permitted by the Fire Department. The modified standard also carries separation distances, detection and suppression requirements, a pre-commissioning emergency response plan, and a hazard mitigation analysis including fire and deflagration testing.

A one kilowatt-hour trigger leaves no tier small enough to escape filing. The same equipment that the NEC now describes as a valid emergency power source is, in the densest indoor market in the country, a permitted and fire-inspected installation from the first unit.

The insurance carve-out. Brown & Brown’s 2026 energy and infrastructure outlook described a softening United States property market, with improved pricing, broader terms and lower deductibles for many insureds. Storage did not ride along. Insurers continue to price thermal runaway at grid-scale lithium iron phosphate installations and, for building-sited systems, fire at commercial storage that can disrupt the host facility, naming storage sited alongside a data center or a critical process as the specific concern. Broker guidance holds that UL 9540A fire testing and IEC 62933 documentation are effectively mandatory before a commercial project binds coverage, on top of a detailed risk assessment.

The underwriting question for a building-sited battery, on that reading, is not whether the battery itself is a total loss but whether the host facility keeps operating. A hospital adding storage to its emergency power system is adding it to a facility whose continuity is the insured interest. The CMS waiver changes what the accreditor will accept. It does not change what the underwriter will charge, and those two approvals are obtained from different people on different timelines.

Occupant communication. Clean Energy Group published a battery storage fire safety FAQ for multifamily housing this month, covered by pv magazine USA, that treats occupant communication rather than equipment listing as the gating condition for in-building storage. The report said residential storage adoption doubled between 2023 and 2024 while emergency incidents declined on improved technology, standards and codes, and set that against roughly 100 deaths a year from portable diesel generators, mostly carbon monoxide poisoning from improper use. It also said that no large-scale United States battery storage fire since 2012 produced widespread contaminant risk. The operational guidance is concrete: the developer and the local permitting authority coordinate, the fire department and the residents are told where the batteries are, and evacuation procedures name the battery system explicitly.

The document addresses multifamily housing, not healthcare occupancies, and Clean Energy Group makes no claim about hospitals. The inference worth drawing is structural rather than evidentiary: a national nonprofit writing a resident-facing explainer indicates that the approval chain for an in-building battery does not end at the authority having jurisdiction. Whether the same dynamic governs a hospital facilities committee is untested in the published material.

Adoption lag. Code editions become enforceable one jurisdiction at a time, and healthcare accreditation organizations routinely trail a cycle behind the published standard. An engineer citing NEC 2026 to an authority still enforcing an earlier adopted edition holds a research project rather than a permit. The first question on any hospital storage proposal for the next two years is which edition the local authority having jurisdiction and the accreditor have actually adopted, and those two answers frequently differ.

The CMS waiver and the 2026 NEC make a battery a candidate component of a hospital life-safety system, and therefore subject to the scrutiny that applies to life-safety systems. New York City’s one kilowatt-hour permitting trigger and the property market’s battery carve-out are that scrutiny in operation. The codes that admit building-sited storage and the regimes that examine it are advancing on the same schedule, and every project between now and the next cycle will be resolved in the space between them.

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