The IECC 2021 Submetering Mandate: A Complete Guide to Subcircuit Monitoring for Commercial Buildings

Which States Are Affected Today?

As of early 2026, the following states and jurisdictions have adopted the 2021 IECC (or ASHRAE 90.1-2019, which contains equivalent metering mandates) for commercial buildings, meaning the submetering requirement is now enforceable law:

Additionally, HUD and USDA published a Final Determination in April 2024 adopting the 2021 IECC and ASHRAE 90.1-2019 as minimum requirements for all federally financed housing programs. This means any project receiving federal housing funds—including FHA-insured multifamily, USDA Rural Development, and HUD-assisted construction—must meet these metering standards regardless of the state’s adopted code. The agencies also accepted the 2024 IECC and ASHRAE 90.1-2022 as alternative compliance paths, signaling that the federal floor will only rise.

States that have not yet adopted the 2021 IECC at the state level are not immune from these requirements. Home rule states like Texas allow major cities to adopt local codes independently, which is why Austin, Dallas, Houston, San Antonio, El Paso, and Killeen have all adopted local codes based on the 2021 IECC even though Texas has no statewide mandatory commercial energy code. Similarly, Colorado mandates that any municipality updating its building code between July 2023 and June 2026 must adopt the 2021 IECC as a minimum, creating a rolling wave of local adoption across the state.

The Technical Requirements: What Must Be Metered and How

Section C405.12 of the 2021 IECC specifies that metering systems must cover five end-use categories through electrical metering (C405.12.1) and end-use metering (C405.12.2):

• Total HVAC System: All electric-powered heating, cooling, ventilation, and air distribution equipment, including chillers, boilers with electric ignition and controls, air handling units, rooftop units, split systems, variable refrigerant flow systems, exhaust fans, and pumps.

• Interior Lighting: All lighting systems located within the building, including general illumination, task lighting, accent lighting, and emergency lighting circuits that also serve normal operations.

• Exterior Lighting: All lighting systems located on the building site but not within the building, including parking lot lighting, pathway lighting, facade lighting, and signage.

• Plug Loads: Devices, appliances, and equipment connected to convenience receptacle outlets, including workstation equipment, kitchen appliances, vending machines, and miscellaneous plug-in loads.

• Process Loads: Specialized equipment and building operations including elevators, escalators, data center equipment, commercial kitchen cooking equipment, laundry equipment, and any other loads not captured in the above categories.

Meters must have a tested accuracy of ±2 percent. Current sensors are permitted in lieu of traditional watt-hour meters provided they meet this accuracy threshold. Building systems that can self-monitor their energy consumption—such as modern variable frequency drives with built-in power metering or building automation system controllers with energy tracking modules—are permitted instead of standalone meters. Not more than 5 percent of the measured load for each end-use category is allowed to come from a load that does not belong to that category, establishing a strict accuracy standard for load disaggregation.

The data acquisition system must store all meter data for at least 36 months. It must be capable of storing real-time energy consumption data and providing hourly, daily, monthly, and yearly logged data for each end-use category. A permanent and readily accessible reporting mechanism must be provided in the building, accessible by building operation and management personnel. This reporting mechanism must have the capability to graphically present energy consumption for each end-use category at hourly, daily, monthly, and yearly intervals for the previous 36 months.

Exceptions exist for Group R-2 occupancies (apartments), individual tenant spaces under 5,000 square feet with their own utility services and meters, and individual tenant spaces under 2,500 square feet with dedicated source meters. End-use submetering is also not required for fire pumps, stairwell pressurization fans, or any system that operates only during testing or emergency.

How Subcircuit Monitoring Actually Works: From Sensor to Dashboard

Subcircuit monitoring is the practice of placing individual metering sensors on each electrical circuit or group of circuits that feed a specific piece of equipment or end-use category, rather than relying on a single whole-building utility meter. The goal is granular visibility—the ability to see exactly how much energy each air handling unit, lighting panel, plug load circuit, or chiller is consuming in real time.

Layer 1: The Sensors at the Circuit Breaker

The monitoring process begins inside the electrical panel. Every circuit breaker in a commercial building feeds a specific load—a rooftop unit, a lighting panel, a receptacle circuit, a kitchen exhaust fan. Subcircuit monitoring places a sensor on the outgoing conductor from each circuit breaker to capture the current flowing through that wire.

Emergent Metering’s primary subcircuit monitoring platform is the Panoramic Power wireless sensor family. These sensors are fundamentally different from traditional current transformer (CT) based monitoring systems. Traditional CT-based systems require a physical current transformer clamped around a conductor, wired back to a central meter with signal cables, and powered by an external source. Panoramic Power sensors are self-powered, wireless, and maintenance-free.

The technology works through electromagnetic energy harvesting. Each sensor clamps directly onto the insulated conductor coming out of the circuit breaker. The sensor detects the magnetic field created by the current flowing through the wire and uses that same magnetic field as its power source. There are no batteries to replace, no signal wires to run, and no external power connections. The sensor harvests enough energy from the magnetic field to power its internal electronics and transmit data wirelessly at 915 MHz (US version) every 10 seconds.

The Panoramic Power sensor family includes four models, each designed for different circuit sizes and applications:

• PAN-10 (0–63 Amps): Designed for small single-phase circuits with a maximum wire outer diameter of 7mm (0.28 inches). Ideal for monitoring individual lighting circuits, small receptacle panels, exhaust fans under 5 HP, unit heaters, and small split-system HVAC units. At $190 per sensor, it is the most cost-effective entry point for circuit-level monitoring.

• PAN-12 (0–225 Amps): Designed for medium circuits with a maximum wire outer diameter of 18.8mm (0.74 inches). Suitable for larger lighting panels, medium rooftop units, small chillers, domestic hot water heaters, and commercial kitchen equipment circuits. Also $190 per sensor.

• PAN-14 (Any Current Range): A high-current sensor that attaches to any standard 0–5 Amp secondary current transformer, allowing it to measure circuits at any current range or wire gauge. This sensor is used when the conductor size exceeds the PAN-12’s capacity—typical applications include main switchgear feeds, large motor circuits, chiller compressors, and central plant distribution. The PAN-14 costs $190 and pairs with external CTs ranging from $40 (100 Amp) to $300 (4,000 Amp).

• PAN-42 (Three-Phase Power Meter): The most sophisticated sensor in the family, designed specifically for three-phase equipment monitoring. Unlike the PAN-10/12/14 which measure current only (with power calculated using configured voltage and power factor in the software), the PAN-42 measures actual voltage and current simultaneously across all three phases, providing true power (kW), reactive power (kVAR), apparent power (kVA), power factor, and energy (kWh) measurements. It supports 4-wire Wye, 3-wire Delta, single-phase 3-wire, single-phase 2-wire, and dual-phase 3-wire configurations at 120V/208V, 240V/416V, or 277V/480V. The PAN-42 is powered through the reference line voltage rather than being self-powered, and works with external 0–5A CTs. At $389, it is the meter of choice for air handling units, rooftop units, chillers, cooling towers, and any three-phase HVAC equipment that the code requires to be monitored.

Layer 2: The Bridge—From Wireless Signal to the Cloud

All Panoramic Power sensors communicate wirelessly to the Gen 4+ Bridge, a compact data collection gateway that serves as the on-site hub for the monitoring system. The bridge receives the 915 MHz transmissions from every sensor within its range (typically up to 5 meters in a panel environment, with the ability to install multiple bridges across a facility) and securely transmits the aggregated data to the PowerRadar cloud platform via the internet.

The Gen 4+ Bridge is available in three connectivity configurations: LAN (hardwired Ethernet), WiFi, and 4G LTE cellular. The LAN version ($370) is preferred when the building’s IT network is accessible near the electrical panels. The 4G LTE version ($470) is used when network connectivity is unavailable, such as in remote mechanical rooms, rooftop penthouses, or buildings under construction where the IT network is not yet active. Emergent Metering also carries tri-carrier 4G SIM cards ($150/year) compatible with Verizon, AT&T, and T-Mobile networks.

In a typical commercial building deployment, one bridge can communicate with dozens of sensors installed in a single electrical room or panelboard area. Larger buildings with multiple electrical rooms simply deploy additional bridges, each feeding data to the same PowerRadar account. The bridge also features an RS485 Modbus port that can be customized to communicate data from external third-party devices—allowing integration of Modbus-enabled gas meters, water meters, BTU meters, and other non-electric energy sources into the same data stream.

Layer 3: PowerRadar—The Unified Front-End Platform

PowerRadar is the cloud-based energy analytics platform that serves as the single front end for all data collected by Panoramic Power sensors, Leviton branch circuit monitors, and any integrated third-party meters. It is the unified pane of glass through which building operators, facility managers, engineers, and ownership groups visualize, analyze, and report on their building’s energy performance. Critically for code compliance, PowerRadar stores all data for 36+ months and provides the hourly, daily, monthly, and annual graphical reports that the 2021 IECC mandates.

The platform is accessible through any standard web browser (no software installation required) and through dedicated iPhone and Android mobile apps. User management allows different access levels—an ownership group can see portfolio-level data across all buildings, while a building engineer sees only their assigned sites, and a tenant can see only their own consumption. Multi-factor authentication protects access to energy data.

PowerRadar’s key features for code compliance and energy management include:

• Site Dashboard: A real-time overview of the building’s total power consumption, number of active sensors and bridges, alert status, and location. The dashboard displays current local temperature alongside consumption data for weather-normalization context.

• Time View: Detailed power (kW) and energy (kWh) consumption timelines for the entire site or any individual device. Users can zoom into any time period—from 10-second intervals to annual trends—to identify consumption patterns, peak demand events, and anomalies.

• Heat Map: A color-coded intensity map that shows consumption patterns across hours of the day and days of the week. Higher consumption shifts toward red, lower consumption toward green. This visualization instantly reveals after-hours energy waste, weekend base loads, and scheduling opportunities.

• Energy Flow (Sankey Diagram): A flow diagram showing how energy moves from the building’s main supply through device categories (HVAC, Lighting, Plug Loads, Process) down to individual devices. The width of each flow represents the magnitude of energy consumption, making it immediately apparent which categories and which specific pieces of equipment are the largest consumers.

• Benchmarking: Side-by-side comparison of consumption between sites or between individual devices. Building owners with multiple properties can compare energy intensity across their portfolio, while engineers can compare the performance of identical equipment to identify underperformers.

• Device Groups: The ability to group individual sensors into logical categories that map directly to the 2021 IECC end-use categories—Total HVAC, Interior Lighting, Exterior Lighting, Plug Loads, and Process Loads. This grouping feature is the mechanism that transforms raw circuit-level data into code-compliant end-use reporting.

• Rules and Alerts: Sophisticated, rules-based event triggers tied to energy patterns, status changes, and consumption thresholds. Alerts are sent via SMS, email, or HTTP post notification. Examples include alerts when HVAC systems operate outside scheduled hours, when a motor’s power draw increases (indicating bearing failure or belt slippage), or when lighting loads exceed expected baselines after a renovation.

• Automated Reports: Pre-defined and customizable report templates including Cost Reports, Sustainability Reports, and Energy Usage Reports. Reports can be generated on-demand or scheduled for automatic delivery on weekly, monthly, or custom intervals. Each report can include power consumption vs. previous periods, carbon footprint calculations (using configurable CO2e factors), tariff-based cost analysis, and trend comparisons.

• Data Export: Raw data can be exported in CSV format for integration with third-party analytics platforms, energy modeling software, or corporate sustainability reporting systems. Auto-export jobs can be configured to push data to external systems on a scheduled basis.

• Pulse Meter Integration: The bridge and PowerRadar platform support pulse output integration from non-electric meters—water meters, gas meters, steam meters, compressed air meters—allowing all building energy data to flow through a single front end. Volumetric pulse data is configured in PowerRadar with the appropriate engineering units and scaling factors.

The combination of wireless sensor hardware and the PowerRadar platform means that a building owner can achieve full IECC 2021 Section C405.12 compliance with no recurring software subscription fees. The PowerRadar Visualize package provides all the monitoring, reporting, and data storage capabilities the code requires at no ongoing cost beyond the initial hardware investment. For organizations that want advanced analytics, predictive maintenance alerts, and custom dashboards, the PowerRadar Optimize package adds additional AI-driven features.

Mapping Specific Equipment to Sensors: A Practical Guide

For engineers and contractors specifying a code-compliant metering system, the key question is: which sensor goes on which piece of equipment? Here is a practical mapping guide:

HVAC Equipment

• Rooftop Units (RTUs): PAN-42 with appropriately sized CTs (typically 100A–600A depending on unit capacity). The PAN-42’s true three-phase power measurement captures compressor staging, fan operation, and electric heat simultaneously.

• Split Systems / Mini-Splits: PAN-10 or PAN-12 on the condensing unit circuit, depending on amperage. Indoor air handler circuits can be monitored separately if on dedicated breakers.

• Chillers: PAN-42 with high-capacity CTs (600A–4,000A). Chillers are typically the single largest electrical load in a commercial building and benefit most from true power measurement.

• Chilled Water and Hot Water Pumps: PAN-12 or PAN-14 depending on motor horsepower. Variable speed pumps with VFDs should be monitored at the VFD input.

• Cooling Towers: PAN-14 with external CT on the fan motor circuit.

• Exhaust Fans / Make-Up Air Units: PAN-10 for fractional HP fans, PAN-12 for larger fans up to 225A.

• Variable Refrigerant Flow (VRF) Systems: PAN-42 on the outdoor condensing unit; individual PAN-10 sensors on indoor unit circuits where separately circuited.

Interior Lighting

• Lighting Panels: PAN-12 on the main feed to each lighting panel, or individual PAN-10 sensors on each lighting circuit within the panel for more granular visibility.

• Emergency/Normal Lighting: PAN-10 on circuits that serve dual emergency/normal function.

Exterior Lighting

• Parking Lot and Site Lighting: PAN-10 or PAN-12 on the exterior lighting panel feed or individual contactor-controlled circuits.

Plug Loads

• Receptacle Panels: PAN-12 on the main feed to receptacle-heavy panelboards, or Leviton S7100 Branch Circuit Monitor (12, 24, or 48 inputs) for per-circuit disaggregation across an entire panelboard.

Process Loads

• Elevators: PAN-42 on the elevator machine room feeder.

• Commercial Kitchen Equipment: PAN-12 on dedicated kitchen panel feeds.

• Data/Server Rooms: PAN-42 on the UPS input and output, PAN-12 on distribution panel feeds.

The Leviton S7100 Branch Circuit Monitor: Panel-Level Disaggregation

For buildings where the electrical design places multiple end-use categories on a single panelboard (a common design approach), the Leviton S7100 Branch Circuit Monitor provides a complementary solution to the Panoramic Power wireless sensors. The S7100 BCM is a DIN-rail or wall-mounted meter that connects to 12, 24, or 48 individual branch circuits through current transformers, simultaneously measuring energy on every circuit in the panel.

The S7100 communicates via Modbus RTU (RS-485) and can be connected to an Obvius/Leviton AcquiSuite data hub or directly to the Gen 4+ Bridge’s Modbus port for integration into PowerRadar. This makes it possible to monitor an entire 42-space panelboard with a single device, assigning each circuit to the appropriate end-use category in the software. The 12-input model ($1,500), 24-input model ($2,400), and 48-input model ($3,000) offer scalability for different panel sizes.

All S7100 data flows into the same PowerRadar front end as the wireless Panoramic Power sensors, maintaining a single unified platform for all building energy data. The device groups and reporting features in PowerRadar can aggregate data from S7100 circuits alongside PAN sensor data, allowing engineers to mix and match monitoring technologies depending on what makes the most practical and cost-effective sense for each panel and each piece of equipment.

Integration Components: Connecting Non-Electric Meters to the Unified Front End

Section C405.13 of the 2021 IECC extends monitoring requirements to nonelectrical energy sources—natural gas, chilled water, hot water, and steam. PowerRadar’s pulse meter integration capability allows these non-electric meters to feed data into the same unified platform:

• Natural Gas Meters: Sierra Instruments and Sage Metering thermal mass flow meters provide pulse output that connects through the Gen 4+ Bridge or an Obvius/Leviton AcquiSuite hub.

• Chilled Water / Heating Water: EES-301 and EES-401 ultrasonic BTU meters measure flow rate and temperature differential with clamp-on transducers. Modbus output feeds directly into the data acquisition system.

• Steam: Vortek Metering Vortex mass insertion meters measure steam mass flow and energy, providing pulse or analog outputs for integration.

• Domestic Water: EES-101 and EES-201 ultrasonic water meters with clamp-on or insertion transducers for non-invasive installation.

• Compressed Air: VPFlowScope and IFM compressed air meters detect leaks and measure CFM consumption for process load monitoring.

The Obvius/Leviton AcquiSuite (A8810, A8812) and the EMHXD Data Acquisition Server provide on-premises data logging with Modbus, BACnet, and pulse input support, storing data locally for 36 months and providing remote web-based access. For larger buildings or campus environments, the Honeywell JACE WEB-8000 and WEB-9000 controllers offer Niagara Framework protocol translation and can aggregate data from hundreds of diverse meter types into a unified interface. All of these integration paths ultimately feed into PowerRadar as the single front-end reporting platform, ensuring that building operators have one place to go for all energy data—electric, gas, water, steam, and thermal—rather than juggling multiple disconnected systems.