Most building owners and engineers have spent the last few years getting comfortable with IECC's submetering rules. That's the right instinct — but it leaves a blind spot. ASHRAE Standard 90.1 carries its own electrical energy monitoring mandate, and in a large share of U.S. jurisdictions, 90.1 is the standard your project is actually being evaluated against. If you've scoped your metering plan around IECC alone, you may be designing to the wrong rulebook.

This guide breaks down what ASHRAE 90.1-2022 Section 8.4.3 requires, the building size where it kicks in, how it diverges from IECC, and what all of that means for the way you lay out meters and sensors.

What ASHRAE 90.1-2022 Section 8.4.3 Requires

ASHRAE 90.1-2022 requires that electrical energy use be monitored by load category — not simply measured at the building's main service. Under Section 8.4.3, electricity consumption must be tracked across the major end-use categories that drive a commercial building's energy profile: total building usage, HVAC systems, interior lighting, exterior lighting, and other significant loads.

The logic mirrors the broader direction of energy codes everywhere. A single whole-building number tells you what you spent; it tells you nothing about where the energy went or what to do about it. By forcing visibility at the load-category level, the standard turns the electrical system into something you can actually manage, benchmark, and improve.

Which Buildings Are in Scope?

ASHRAE 90.1-2022's monitoring requirements generally apply to buildings larger than 25,000 square feet. For those buildings, separate monitoring of the major load categories is a condition of compliance, not an optional upgrade.

That 25,000-square-foot line is one of the most important numbers in this conversation, because it's where ASHRAE 90.1 and IECC part ways — and where teams make costly assumptions.

How ASHRAE 90.1 Differs From IECC

If you've read our IECC 2021 Submetering Mandate guide, the overall shape will look familiar. But the differences in the details are exactly the kind that get projects flagged at review.

The biggest divergence is the size threshold. The 2024 IECC lowered its submetering threshold to 10,000 square feet, pulling a large population of small and mid-size commercial buildings into scope for the first time. ASHRAE 90.1-2022's monitoring requirement applies at 25,000 square feet. The practical consequence: a 15,000-square-foot building can be fully obligated under IECC while sitting below ASHRAE 90.1's threshold. Knowing which standard governs isn't academic — it can be the difference between a compliant project and a failed inspection.

The two standards also frame the requirement differently. IECC's recent cycles have expanded prescriptive submetering of specific end uses, including non-electrical loads addressed in Section C405.13.7 — boilers, chillers, furnaces, and similar equipment. ASHRAE 90.1's Section 8.4.3 is organized around electrical energy monitoring by load category. A well-designed metering plan can satisfy both, but only if it's scoped from the outset to the stricter of the two requirements that apply to your building.

Which Standard Applies to Your Project?

This is where even experienced teams get tripped up. The energy code in force depends entirely on your jurisdiction's adoption. Some states and municipalities adopt IECC; some adopt ASHRAE 90.1 as an alternative compliance path; many reference both and let the design team choose. Your project might be permitted to comply via either standard — or be required to meet one specific version.

The safe design posture is to identify both thresholds early in design development and meter to whichever standard pulls your building into scope at the lower bar. Assuming you're exempt because you cleared one threshold is the single most common — and most expensive — mistake we see, because the remedy usually arrives as rework after the panels are already built.

What This Means for Your Metering Design

Translating the code language into a buildable plan comes down to a few principles.

First, design to load categories, not just the main service. Whether you land under ASHRAE 90.1, IECC, or both, the requirement is granular: HVAC, interior lighting, exterior lighting, and other major loads need to be separable and individually measurable. Planning the circuit layout around those categories during design — rather than discovering the requirement during submittal review — is what keeps the project on schedule and on budget.

Second, confirm your threshold before you assume you're exempt. A building under 25,000 square feet is not automatically clear; IECC's 10,000-square-foot threshold may still apply and may pull in additional end uses. Map both standards against your gross floor area before making any exemption call.

Third, choose a metering approach that produces usable data, not just a compliance checkbox. This is the difference between spending money and investing it. Circuit-level monitoring that feeds real-time dashboards and automated reporting converts a code obligation into operational visibility your team can act on every day — the same data that verifies retrofit savings, supports benchmarking and Building Performance Standards reporting, and flags equipment drift weeks before failure.

How Wireless Submetering Satisfies the Requirement Without Disruption

The usual objection to adding load-category metering in an existing building is downtime: you can't shut operations to rewire panels. Wireless, self-powered sensors remove that barrier. They clamp onto existing circuits with no shutdown, no panel rebuild, and no rewiring — so the building keeps running while monitoring goes live. For new construction, designing sensor placement around the required load categories from the start makes ASHRAE 90.1 (and IECC) compliance a planned outcome rather than a scramble.

The Bottom Line

ASHRAE 90.1 submetering doesn't have to be a cost you simply absorb to pass review. Scoped correctly — to the right threshold, around the right load categories, with the right metering technology — it becomes the foundation for genuinely understanding how your building uses energy.

Not sure whether ASHRAE 90.1 or IECC governs your project's metering requirements? Schedule a platform demo and we'll help you map the obligations to your specific building.