LoRaWAN Electricity Sub-Metering Systems

What is Electricity Sub-Metering

You have one main meter from the utility. It tells you total building consumption. But which tenant used what? Which EV charging station drew how much power? Is your solar installation actually producing what the salesman promised?

You don't know. That's the problem sub-metering solves.

Sub-meters measure consumption at the unit, circuit, or equipment level. Each apartment gets its own meter. Each EV charger gets tracked individually. Each solar inverter gets monitored separately. Then you know exactly what's happening - who's using what, what's wasting energy, what's underperforming.

Without sub-meters, you split bills equally (unfair to light users) or estimate (causes disputes). With sub-meters, you bill based on actual consumption and find energy waste you didn't know existed.

LoRaWAN Advantages for Electricity Monitoring

No data cables through electrical panels: Traditional sub-metering requires wired connections (RS-485, Ethernet) from meters to collection systems. LoRaWAN operates at 868MHz (EU) or 915MHz (US) - signals penetrate concrete walls and metal enclosures. Install meters anywhere without running data cables.

Power harvesting options: CT clamps can harvest power from measured current - no batteries or external power needed. Devices like the Milesight CT101 use supercapacitors charged from the measured current itself. Other options use replaceable batteries lasting 5-10 years.

Scalability: One LoRaWAN gateway covers entire building complex, solar farm, or RV park. Add meters without network infrastructure changes - just provision new devices and they join the network. Single gateway handles hundreds of meters.

Installation without downtime: CT clamps install without breaking circuits or shutting off power. Licensed electrician clamps around existing conductors in seconds. No service interruption.

Hardware Options

CT Clamp Sensors

Self-powered CT clamps (Milesight CT101 and similar):

Current transformers harvest power from measured current using supercapacitors. Zero maintenance—no batteries to replace ever. Clamp-on installation around L1, L2, or L3 conductors takes seconds without breaking circuits or interrupting service. Models typically measure up to 100A or 300A depending on variant. Accuracy specs vary by manufacturer, with typical CT clamps offering acceptable accuracy for billing and monitoring applications.

Critical limitation: Self-powered CT clamps require at least 400W continuous power draw through the measured conductor to sustain supercapacitor charge and maintain 1-minute uplink intervals. Below 400W, the supercapacitor cannot charge sufficiently and the device stops transmitting. This is measured real-world behavior—not theoretical specs. The device needs constant power flow above this threshold or it fails to operate.

This makes self-powered CT clamps completely unsuitable for:

• Low-power circuits (lighting, small appliances, individual outlets)
• Intermittent loads (EV chargers when not charging, equipment with duty cycles)
• Circuits with frequent off periods (anything that turns off overnight or on weekends)
• Individual apartment circuits (typically 200-1000W peak, not continuous)

Alternative power option: The CT101 can be powered via USB-C 5V instead of harvesting from measured current. This enables monitoring circuits below 400W or intermittent loads that don't provide continuous power. External power eliminates the minimum current requirement entirely—you can measure any circuit regardless of load. Useful for temporary monitoring, low-power circuits, or situations where you need guaranteed operation independent of measured current. Requires running USB power cable to the installation location.

Use battery-powered alternatives for permanent installations on circuits below 400W where running USB power isn't practical. Self-powered mode only works for high-power, always-on circuits—main building feeds drawing kilowatts continuously, industrial equipment that never stops, central HVAC systems, or data center power distribution.

Battery-powered CT clamps:

Alternative to self-powered models using replaceable batteries lasting multiple years depending on transmission frequency. Sometimes more accurate than self-powered variants. Options include Adeunis ARF8180AA and Elsys EMS among others. Trade battery replacement maintenance for potentially better measurement precision.

Three-phase monitoring: Install 3 CT clamps for three-phase systems. Measure each phase individually. Calculate total power, detect phase imbalance, monitor power factor.

DIN Rail Energy Meters

Panel-mounted meters:

Install in electrical distribution boards on standard DIN rails. More accurate than CT clamps due to direct measurement of both voltage and current, calculating true power in watts. Require licensed electrician installation since circuits must be de-energized during installation—not suitable for retrofit without planned downtime. Revenue-grade models offer the highest accuracy when billing precision matters legally. Features include cumulative kWh tracking, power factor measurement, and total harmonic distortion (THD) monitoring. LoRaWAN integration options include Modbus meters paired with LoRaWAN gateways or integrated models with native LoRaWAN connectivity. Best suited for new construction, panel upgrades, or applications demanding high accuracy.

Smart Plugs with LoRaWAN

Individual appliance monitoring without panel modifications. Plug between wall outlet and device to track consumption of specific equipment temporarily or permanently. Handles moderate loads suitable for plug-in appliances—not hardwired equipment or high-power devices like HVAC systems or industrial machinery. Useful for tracking specific appliances, temporary monitoring during energy audits, or situations where panel access isn't feasible.

Applications

Solar Production Monitoring

Sub-meter solar inverter output separately from building consumption to track generation versus consumption patterns in real-time. Systems measure solar production in kWh generated, building consumption in kWh used, grid import/export for net metering accounting, and calculate self-consumption percentage automatically. This enables accurate ROI calculation on solar installations by revealing actual energy offset versus projections. Optimize consumption timing to maximize self-consumption during daylight hours—running washing machines, charging EVs, or heating water when panels produce surplus power. Identify opportunities to charge battery storage or delay high-power loads based on generation forecasts.

EV Charging Stations

Each charging point gets individual sub-meter. Bill users based on actual kWh delivered, not flat rates.

Implementation: CT clamps on each charger circuit. Monitor current draw, calculate energy delivered. Integrate with billing system or RFID card readers.

Load balancing: Monitor total facility power vs available capacity. Throttle chargers dynamically to avoid exceeding grid connection limits. Prioritize charging based on user tier or vehicle SOC.

RV/Camper Electrical Hookups

Campgrounds with electrical hookups meter individual sites. Charge based on usage instead of flat daily rates.

Typical setup: Each site has 15A, 30A, or 50A service. CT clamp on feed to each site pedestal. Dashboard shows current usage, alerts when approaching amperage limit.

Billing: Calculate kWh consumed during stay. Generate invoice at checkout. Detect usage patterns (e.g., running AC all night) that justify dynamic pricing.

Multi-Tenant Buildings

Individual apartments or commercial units get electricity sub-meters enabling fair billing based on actual consumption. Buildings with central HVAC but individual unit appliances benefit from separating common area from unit-specific usage. Commercial buildings with mixed tenants—office spaces, retail stores, restaurants—each have vastly different consumption patterns requiring individual metering for fair cost allocation. Industrial facilities with multiple tenants sharing a building need accurate measurement to avoid disputes and ensure each tenant pays only for what they consume.

Implementation typically uses CT clamps on the main feed to each unit for retrofit scenarios, or DIN rail meters for higher accuracy when panel space is available during construction or upgrades. Automated monthly billing integration eliminates manual meter reading and invoice generation.

Industrial Equipment Monitoring

Track consumption per machine, production line, or process to enable data-driven operations. Preventive maintenance programs detect bearing failures or motor degradation through increased current draw before catastrophic failure occurs. Energy efficiency audits identify inefficient equipment consuming more power than necessary—providing justification for replacement or repair. Production cost allocation attributes energy costs to specific products or batches, improving cost accounting accuracy. Load shedding programs disable non-critical equipment during demand response events, reducing peak demand charges that can represent significant portions of industrial electricity bills.

Data Pipeline

LoRaWAN gateway receives meter transmissions and forwards them to a Network Server—ChirpStack, The Things Network, or commercial alternatives. The network server decodes packets and pushes data to InfluxDB or similar time-series database. Grafana or custom dashboards query the database for visualization and alerting.

Data collection:

Systems store instantaneous power in watts, cumulative energy in kWh, voltage, current in amps, power factor for three-phase installations, and frequency. This raw data feeds calculations, visualizations, and billing systems. Historical data enables trend analysis revealing consumption patterns over days, weeks, or months.

Visualizations:

Real-time power consumption graphs show current load at a glance. Daily, weekly, and monthly kWh totals summarize consumption for billing periods. Cost tracking based on utility rate structures—including time-of-use pricing where rates vary by hour—translates energy data into financial impact. Load profile heatmaps visualize when consumption occurs throughout the day, identifying peak usage periods. Comparative analysis across units or tenants highlights outliers consuming significantly more or less than similar spaces.

Alert conditions:

Configure alerts triggering when usage exceeds contracted capacity to enable demand limiting before utility penalties apply. Voltage outside normal operating range indicates grid problems or equipment issues requiring investigation. Current imbalance exceeding thresholds on three-phase systems signals wiring problems or uneven load distribution. Power factor below acceptable levels warns of inefficiency that may incur utility penalties. Equipment showing zero current when it should be running indicates failures requiring immediate attention.

System Design Considerations

Gateway placement: Central location with sight lines to electrical panels and meter locations. Electrical rooms often work well - metal enclosures create RF shielding, so test coverage before finalizing placement. For large buildings with multiple floors or metal structures, plan for multiple gateways or external antennas.

CT clamp sizing: Match CT clamp range to expected current. 100A CT on 200A circuit won't work. Undersized CT clamps saturate and give false readings. Oversized CTs sacrifice low-end accuracy. Rule of thumb: size CT for 150% of maximum expected current.

Voltage reference: CT clamps measure current only. To calculate power (Watts = Volts × Amps), you need voltage. Options:

• Assume fixed 230V (3-5% error typical)
• Use voltage reference sensor in panel (more accurate)
• DIN rail meters measure both V and I directly

Transmission frequency:

Balance between data freshness and battery life for battery-powered models. More frequent transmissions provide better real-time visibility but drain batteries faster. Longer intervals extend battery life at the cost of data granularity. Ten-minute intervals suit real-time monitoring applications, thirty-minute intervals offer a good compromise for most use cases, and hourly transmissions provide sufficient data for billing while maximizing battery longevity. Actual battery life depends on temperature, transmission power, and specific hardware—consult manufacturer specs for estimates.

Self-powered models transmit based on current flow and have no battery considerations—but remember they require continuous power above 400W to function at all.

Network server choice:

• Self-hosted ChirpStack: Full control, no per-device fees, requires sysadmin
• The Things Network: Free, fair use limits, good for small deployments
• Commercial providers: Managed service, SLAs, higher cost

Billing Integration

Manual billing: Export monthly consumption reports as CSV. Import into billing software or create invoices manually. Works for small deployments (<20 units).

Semi-automated: Scheduled report generation (monthly). Staff reviews for anomalies (zero consumption = meter offline, 10x normal = wiring error). Adjust before invoicing.

Fully automated: API integration between metering database and billing system:

• Automatic invoice generation based on rate tables
• Time-of-use pricing (peak/off-peak rates)
• Demand charges (based on peak 15-minute interval)
• Exception handling for unusual patterns
• Integration with property management software

Common Implementation Mistakes

CT clamp orientation: CT clamps have polarity. Installing backwards shows negative power (generation instead of consumption). Mark conductor direction before installation.

Measuring neutral instead of phase: CT must clamp around phase conductor (L1, L2, L3), not neutral (N) or ground (PE). Neutral current only reflects imbalance on three-phase systems.

Metal enclosure shielding:

LoRaWAN signals attenuate significantly passing through metal electrical panel enclosures. Test coverage with panel door closed before finalizing installation. May need external antenna or gateway placement near panels to overcome shielding.

No calibration verification: CT clamps arrive factory-calibrated but transport damage occurs. Verify accuracy against known load before deployment. ±3% spec can become ±10% if damaged.

Single-phase monitoring of three-phase loads: Measuring one phase of three-phase load gives 1/3 of total (at best). Need CT on each phase. Calculate total power = P1 + P2 + P3.

What I Provide

Services:

• System design: CT sizing, meter placement, panel analysis
• Gateway placement planning and RF coverage modeling
• Hardware specification and sourcing guidance (Milesight, Adeunis, Elsys, etc.)
• Network server setup (ChirpStack recommended for self-hosted)
• Data pipeline implementation (InfluxDB + Grafana or custom dashboard)
• Power calculation algorithms (real power, reactive power, power factor)
• Billing integration design (rate tables, time-of-use, demand charges)
• Alert rule configuration
• Load balancing logic for EV chargers or demand response

You own everything:

• Complete source code for data processing and dashboards
• Self-hosted infrastructure (or cloud if you prefer)
• All configuration documentation
• Device provisioning procedures
• Billing integration code
• No monthly platform fees after implementation

Hardware (you source):

• CT clamp sensors (Milesight CT101, Adeunis ARF8180AA, Elsys EMS)
• DIN rail energy meters (optional, for higher accuracy)
• LoRaWAN gateway(s)
• Server (on-premise or VPS) for network server and database

I don't sell hardware. I specify what you need, help you source it, and build the software that makes it work for your specific application.