Lunar System meets all of the new requirements of UL 9540A 6th Edition

There’s a new version of UL 9540A — the standard that governs how residential battery systems are evaluated for fire safety. The 6th Edition, published in 2026, is the most comprehensive update since the standard was introduced. As of this month, the Lunar System already complies with it.

Here’s what that means, and why it matters for every installer putting our system in the field.

UL 9540A

UL 9540A is the test method used to evaluate thermal runaway fire propagation in battery energy storage systems. In plain terms, it answers the question of what happens if a battery cell fails, and whether that failure can spread to adjacent units, wall surfaces, or the structure of a home.

The standard is referenced by the International Fire Code and adopted by jurisdictions across the country. In many markets, UL 9540A compliance isn’t optional; it’s a condition of permit approval.

What changed in the 6th Edition — and why it matters

The 6th Edition introduced large-scale fire testing as a formal requirement — replacing the previous installation-level test in section 10 of the 5th Edition. For residential installations greater than 20 kWh, this new testing is required if the product is unable to meet the unit-level requirements. 

Here’s the important takeaway: every Lunar System configuration — from 10kWh to 30kWh — fully complies with the 6th Edition’s new unit level requirements. Our UL 9540 Certified 5kWh modular DC ESS unit meets every performance criterion of the new 9540A 6th Edition Unit level Test. Therefore, every installed configuration of the Lunar System isn’t required to do additional installation-level large-scale fire testing. 

What this means for installers

As battery installations become ubiquitous, jurisdictions are adopting the latest fire codes and demanding more rigorously tested products requiring both UL 9540A compliance and large-scale fire test documentation before approving a residential battery installation. At the same time, demand for batteries with more energy capacity is growing to meet rising power demands. That creates a real obstacle at the AHJ level.

But with the Lunar System, this obstacle is already cleared — creating a smoother residential installation pathway because our product already meets the increased performance criteria in the 6th Edition for installations greater than 20kWh.

In practice, that means simpler permitting. When an AHJ asks for fire safety credentials, the answer is complete.

Fire safety standards exist for good reasons. We’re glad that our products continue to set an example for safety.

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