Quick Summary (TL;DR)
For a typical 6–16 circuit distribution board, start by choosing the measurement boundary, not the number of clamps advertised on the box. If you want a single view of many individual final circuits, the Emporia Vue 3 offers up to 16 branch CT inputs per unit and separate main-service inputs, but its normal operation and app depend on the Emporia cloud. If you prioritise open, locally managed data, the current OpenEnergyMonitor emonPi3/emonTx6 family provides six CT inputs per node and can expand by adding nodes. CircuitSetup’s expandable ESP32AliExpress price board is more configurable and potentially larger, but is an engineering project, not a drop-in certified consumer-unit appliance.
A Shelly Pro 3EM 120A v2 is an excellent three-channel local monitor, not a sixteen-circuit system. Several Shelly devices can be deployed where there is adequate panel space, network coverage and a sensible cost case. Professional PowerTag systems can instrument many circuits with purpose-built sensors and gateways, but require a compatible switchboard design, an installer and a substantially different purchasing process. One CT channel is not always one useful circuit: three-phase loads, split-phase loads, grouped feeds and sub-panels can consume multiple channels or create overlapping totals.
The right purchase depends on whether you have single-phase 230 V, UK three-phase 400/230 V, North American split-phase 120/240 V, or another arrangement; the physical layout of the board; how the readings reach Home Assistant; and who will maintain the system. This guide compares real hardware families and their verified limitations as of 14 October 2026, rather than inventing an accuracy test or a universal installed price.
The shortlist: five ways to monitor multiple circuits
| System / approach | Practical CT or sensor scale | Data path to Home Assistant | Best fit | Most important catch |
|---|---|---|---|---|
| Emporia Vue 3 | Up to 16 branch CT inputs plus up to three dedicated main CT ports per device | Emporia cloud; community integrations are unofficial | A compact, appliance-by-appliance dashboard with minimal custom firmware | Requires internet/cloud; 16 inputs do not guarantee 16 independent three-phase loads |
| OpenEnergyMonitor emonPi3 + emonTx6 | Six CT inputs per node; add further six-channel nodes | Local EmonCMS/MQTT; ESPHome with compatible emonWiFi hardware | Local-first monitoring with understandable data and distributed boards | Budget for voltage-sensing unit, CTs, base/transport and configuration |
| CircuitSetup expandable six-channel ESP32AliExpress price | Six on main board; vendor documents add-on stacking up to 42 total | ESPHome native API / local Home Assistant, subject to firmware and design | Technically confident builders needing custom channel count | Open hardware needs enclosure, electrical review, calibration and ongoing maintenance |
| Multiple Shelly Pro 3EM v2 / Pro EM-50 | Three CT channels per Pro 3EM v2; two per Pro EM-50 | Official Shelly integration over local network | Small set of important feeds and clean DIN-rail architecture | Not economical or space-efficient by default for a dense 16-circuit board |
| Schneider PowerTag Energy + compatible Panel Server | Per-sensor, expandable; supported-device ceiling varies by gateway model | Gateway Modbus TCP/IP or vendor software; integration engineering required | New or professionally refurbished distribution boards | Sensor/breaker/gateway compatibility and project cost must be designed together |
These are different product categories. A whole-home meter plus a few submetered feeders may answer more useful questions than a nominal sixteen-channel product whose sensors do not physically fit. Conversely, buying three-channel equipment for sixteen genuinely separate branches can multiply labour, communications endpoints and enclosure space. The relevant official specifications are Emporia Vue 3, OpenEnergyMonitor emonPi3/emonTx6, CircuitSetup hardware documentation, Shelly Pro 3EM v2 and Schneider EcoStruxure Panel Server.
First count what you need to measure, not the breakers
A domestic consumer unit may contain twelve labelled protective devices but not twelve independent measurement requirements. A kitchen ring final circuit is one monitored branch despite several socket outlets. A three-phase EV charger is one functional load but may require three phase-current measurements. A heat pump may have a separate immersion heater or backup heater circuit that deserves its own CT. Solar generation may be measured at the inverter output while the grid meter sees net import or export. If an upstairs sub-board is monitored at its feeder, counting all its final circuits as well duplicates that energy in a naive sum.
Prepare a circuit schedule with the installer before ordering. Note protective-device label, nominal voltage, number of live conductors, accessible measurement point, approximate operating current, bidirectional possibility and whether that reading is useful for a decision. Leave spare inputs for loads that will arrive later, but do not buy a second monitoring chassis solely because a light fitting could be monitored separately.
| Example load or boundary | Functional loads | Likely current channels to plan | Why the number may change |
|---|---|---|---|
| Single-phase cooker radial | One | One CT on the appropriate conductor | May be shared with another appliance or have unusual wiring |
| Three-phase EV charger | One | Typically three phase CTs | Some metering systems have native three-phase groupings; others need explicit aggregation |
| Single-phase solar inverter output | One | Usually one | Three-phase inverter generally needs three phase measurements |
| Main grid connection, three-phase | One boundary | Typically three main CTs | These may be separate dedicated ports, not branch ports |
| Sub-board feeder, three-phase | One boundary | Typically three | Its downstream final circuits must not be double-counted in totals |
| North American 240 V two-pole load | One | One or two depending on wiring and supported method | One-sensor multipliers are not universally valid for unbalanced loads |
This is a planning illustration, not an installation wiring diagram. CT position, conductor selection, phase-voltage reference and protective arrangement must be confirmed by a competent electrician. Emporia’s own CT installation guidance distinguishes the two-sensor method from limited cases where a multiplier can be used. Do not apply a generic multiplier to an unbalanced load or to the mains of a modern Vue.
Emporia Vue 3: dense circuit coverage, cloud dependence
The current Vue 3 is attractive when the goal is to see many household loads with comparatively little equipment. The manufacturer specifies up to 16 individual 50 A branch CT inputs and up to three 200 A main CT inputs. A two-main-CT kit suits common North American split-phase services; the separate three-phase kit includes three main CTs. Its supported topologies include single-phase two-wire, split-phase three-wire and three-phase four-wire earthed-neutral Wye systems; it is not a universal solution for every Delta or unusual service. Emporia lists up to 264 V line-to-neutral, 2.4 GHz Wi-Fi and Ethernet, with CE and UKCA markings alongside US approvals. Verify the actual product SKU and country supply arrangement before importing a kit.
The main ports form a single service measurement, whereas the sixteen branch ports are for downstream circuits. A large three-phase load still requires a measurement plan for all its phase conductors; the device does not magically turn one CT into a complete three-phase submeter. Its 50 A branch sensor rating also matters: do not choose a CT merely because the breaker label looks familiar. Where a board has awkward busbars or little space around the main conductors, Emporia sells separate flexible main sensors; these add their own integrator and power-supply requirements.
Critical integration distinction: Emporia explicitly states that Vue products do not expose a supported local API, and that it does not offer a public API. Standard telemetry passes through Emporia’s servers. Home Assistant integrations built by the community may access that cloud data, but they are not manufacturer-supported, local or guaranteed to survive a service change. Emporia’s published app documentation also states that local historical storage is not supported. For a property where monitoring must continue without internet, this is a disqualifying limitation unless you accept an independently supported alternative.
For more than sixteen branch inputs, Emporia documents Combined Vues for independent branches in one board and Vue Nesting for a main/sub-board hierarchy. These are not interchangeable: nesting is about measurement boundaries and avoiding duplicate totals, not just increasing the number on a chart. Check the current app’s feature set and licence terms at purchase, rather than assuming an undocumented local API or indefinite free cloud access. Official references: Vue 3 three-phase product specifications, Emporia developer access statement, March 2026 and monitoring more than sixteen circuits, August 2026.
OpenEnergyMonitor: the current emonPi3 and emonTx6, not the older kit
A frequent shopping mistake is to compare a new Vue 3 with an older emonPi2 or emonTx5 listing and treat their expansion options as current. OpenEnergyMonitor’s emonPi3 and emonTx6 succeeded those models in 2026. Each current unit provides six CT inputs, a precision emonVS voltage/power input and support for single- and three-phase monitoring. The emonPi3 includes a Raspberry Pi-based local logging platform; the emonTx6 is a monitoring node that can send data to a base or through supported serial/Wi-Fi arrangements. These are genuine six-channel devices: adding an emonTx6 creates another six measured inputs, rather than unlocking dormant ports in the first box.
The official documentation distinguishes current models from historical emonPi2 expansion boards. In particular, the earlier emonPi2 plus expansion board could offer twelve CT inputs in certain configurations, but the current emonPi3 is documented with six CT inputs. Do not order a twelve-channel emonPi3 expander on the assumption that an old accessory exists for the new platform. The manufacturer’s 2026 hardware release and current overview are the right starting point. Multiple nodes can cover separated consumer units; the installer must still plan the voltage reference, radio path or other data transport and correct channel grouping.
OpenEnergyMonitor is strongest when you want control over how measurements are logged. The vendor documents Home Assistant routes using MQTT from an emonHub-based installation, an EmonCMS integration where feeds already exist, and ESPHome via the supported emonWiFi expander. These paths have different dependencies: a Raspberry Pi with local EmonCMS provides a useful independent history; an emonTx6 with emonWiFi can feed Home Assistant directly; a radio node needs a suitable receiving base. The official Home Assistant integration guide explains which route applies to each hardware generation.
Budget the complete system: six-channel measurement node, appropriate voltage sensor and power arrangement, six or fewer compatible CTs, any additional emonTx6 nodes, data receiver or emonWiFi module, enclosure/mounting, storage and electrician time. A bare six-channel transmitter price is not the installed price of a six-channel monitoring system. CT type matters: current-generation devices have defined sensor compatibility and calibration options, so do not mix old current-output CTs with newer voltage-output inputs without verifying the exact hardware documentation.
CircuitSetup expandable ESP32: maximum flexibility, maximum ownership
CircuitSetup’s expandable six-channel energy meterAliExpress price is the DIY-oriented choice for readers who want their own channel map, firmware and local Home Assistant entities. The manufacturer’s project documentation specifies six CT channels on the main board, two ATM90E32 metering ICs and an add-on-board architecture documented up to six add-on boards, or 42 CT channels in total. That is a board-stack capability, not a claim that every configuration is an easy, compact or electrically suitable residential installation. The ESP32AliExpress price board, CTs, appropriate AC voltage reference, stable power, insulation, physical mounting and network link must all be planned.
The firmware ecosystem is well documented: ESPHome has an official ATM90E32 sensor component with per-channel power, current, voltage-related settings, forward and reverse energy readings and calibration support. The official component documentation emphasises the importance of matching each CT to the correct voltage phase for meaningful real power and power factor. A three-phase installation requires a proper voltage-reference strategy, not simply six current clamps connected to a single-phase calibration profile. The manufacturer’s board documentation and ESPHome installation path should be checked against the revision actually purchased.
This system is not a shortcut around electrical standards. The bare board is an electronic subsystem. It must not be mounted loose among mains terminals, and a design that works on a workbench is not automatically approved for installation in a domestic distribution board. A qualified professional should decide whether it belongs in a suitable separate low-voltage enclosure, how isolated voltage sensing is provided and whether the final arrangement meets local regulations. The builder owns firmware updates, calibration, backup, recovery and troubleshooting. For someone who wants to configure once and forget, that ownership cost may outweigh the apparent hardware saving.
If your main objective is to learn how CT measurements work, our ESP32 CT clamp energy monitor guide explains the measurement principles. The board-stacking project discussed here is different: it is about building a reliable, documented, multi-circuit monitoring service with dozens of data entities and a maintainable circuit schedule, not merely reading one CT in a prototype.
Shelly: good for targeted feeders, less compelling for sixteen branches
Shelly’s Pro 3EM 120A v2 is a DIN-rail energy meterAliExpress price with three supplied 120 A CTs. It supports local LAN/Wi-Fi communications, MQTT, HTTP and WebSocket/RPC capabilities, and it is supported through the official Home Assistant Shelly integration, which communicates directly with the device without requiring Shelly Cloud. It is useful for whole-home three-phase monitoring, solar import/export boundaries or a small set of carefully chosen feeders. It does not provide sixteen independent branch CT inputs. Also, it is a meter, not an integral switching relay: external control requires appropriate separately specified equipment.
Shelly also offers the Pro EM-50, a two-channel 50 A CT-based DIN-rail meter with a separately specified low-current switching output. It is not a general-purpose replacement for an EV charger contactor, and its 2 A output rating must not be confused with the measured CT current. A system built from several two- or three-channel meters may be neat when circuits are spread across different cabinets, but each unit requires installation, protection, network configuration, documentation and maintenance. Count the aggregate number of physical devices, not just the nominal CT ports.
An important detail in the current Pro 3EM v2 documentation is the specified low-load behaviour: Shelly describes a no-load threshold affecting accumulated energy statistics below the stated threshold, while instantaneous readings may still be displayed. For small standby loads, evaluate whether this behaviour matters. The manufacturer also distinguishes accuracy across current ranges and describes device-side historical storage; do not transfer these specifications to a different Shelly generation or 400 A variant. Verify the precise Pro 3EM v2 listing and the Pro EM-50 knowledge-base specification before choosing CTs or planning a board.
Schneider PowerTag: an engineered panel system, not a consumer add-on
Schneider Electric’s PowerTag Energy approach measures individual outgoing circuits using compatible wireless sensing devices and a matching gateway. Current EcoStruxure Panel Server models can aggregate PowerTag Energy and other supported devices and provide interfaces including Modbus TCP/IP, subject to model and firmware. The manufacturer’s guide documents different device ceilings for Entry versus Universal/Advanced gateways, and compatibility depends on the exact sensor family, switchgear and gateway revision. These maximum device figures are not promises of an equal number of monitored domestic final circuits.
PowerTag is worth considering during a planned consumer-unit or small commercial distribution-board redesign, particularly where the electrician or panel builder already uses Schneider equipment. It is usually not the simplest route to add twelve sensors to an arbitrary older household board. Allow for compatible protective devices, the sensors themselves, gateway, commissioning software, available RF environment, licensing or software obligations where applicable, panel testing and documentation. Do not assume that a product carrying the PowerTag name works with any legacy PowerTag Link gateway; some older Link products have been discontinued in certain markets.
A Panel Server exposing Modbus TCP registers is not the same thing as an official plug-and-play Home Assistant integration. The Home Assistant Modbus integration can read documented registers, but you must confirm that the selected gateway and sensor data are actually exposed with the necessary permissions and firmware. Consult the current Schneider supported-device matrix and limits and obtain a written parts schedule from an authorised installer. For a typical retrofit where Home Assistant is the only consumer, this is a professional option rather than the default best-value purchase.
How many sensors will physically fit?
The limiting factor in a busy board is often usable conductor access, not the nominal number of CT sockets. Split-core clamps have a window diameter, external dimensions, lead length and bend-radius constraints. A sensor must be placed around the correct conductor at a safe location without stressing terminals, crushing insulation, compromising protective covers or defeating clearances. Moulded busbars, closely spaced RCBOs, solid links, crowded neutral bars and meter seals can make a proposed layout impossible without a redesign.
| Check before buying | What to record | Why it changes the quote |
|---|---|---|
| Panel type and usable space | Consumer unit model, enclosure material, DIN-rail and wiring-space photographs taken safely by installer | Some systems need an external enclosure; some gateways need additional rail space |
| CT mechanical fit | Outside size, jaw/window size, cable route, cable length and actual conductor diameter | A rated CT may not close around the available conductor |
| Circuit identity | Up-to-date board schedule and any mixed/shared neutrals or multiwire branches | Incorrect grouping produces misleading results and may be unsafe |
| Phase reference | Supply topology and which phase each CT measures | Incorrect voltage reference can make active power and export signs wrong |
| Power and communications | Auxiliary supply, breaker/protection, Ethernet/Wi-Fi/RF and UPS requirements | A meter with 16 ports can still be offline behind a metal enclosure |
| Ownership and access | Who can reach the equipment, upgrade firmware and export data | Tenants, installers and cloud accounts complicate maintenance |
For current-transformer sizing and sensor-output compatibility, read our CT selection guide. A 200 A main CT is not automatically the best sensor for a 6 A lighting circuit; likewise, a 50 A branch CT must not be used outside its specified range. Manufacturer instructions override generic advice. The installer should confirm suitable isolation, enclosure suitability and protective-device arrangements without exposing the homeowner to live conductors.
Regional compatibility: UK and Europe are not North American split-phase
The fact that a monitor is advertised globally does not mean every kit suits every grid. Most UK and continental European homes use nominal 230 V line-to-neutral at 50 Hz, sometimes with a three-phase 400/230 V supply. Typical North American homes use 120/240 V split-phase at 60 Hz, with two line conductors 180 degrees apart. A US kit with two main CTs is not equivalent to a European three-phase kit with three mains CTs. A three-phase four-wire Wye product may not be suitable for an unearthed or Delta service even when the nominal voltage looks similar.
| Supply or installation | Practical implication | Purchase check |
|---|---|---|
| UK single-phase 230 V, 50 Hz | Usually one mains CT for one line conductor; branch CT count depends on circuits | Correct voltage sensing, frequency, product approvals and board clearance |
| UK/EU three-phase 400/230 V, 50 Hz | Three phase-current measurements for a complete mains boundary; some loads span phases | Three-phase compatible model, three mains CTs, correct phase reference |
| North American 120/240 V split-phase, 60 Hz | Usually two mains CTs; two-pole branches can require two CTs for accurate unbalanced measurement | Split-phase support, correct voltage and frequency, local listing |
| Commercial three-phase or unusual earthing | Wye/Delta and neutral arrangements can differ materially | Vendor’s exact topology diagram and electrician’s written approval |
| Outdoor or damp enclosure | Most listed home monitors are indoor/dry-location devices | Rated cabinet and temperature/environmental limits |
In Great Britain, electrical work should be assessed against the applicable BS 7671 Wiring Regulations and the relevant building regulations, including Part P requirements in England and Wales where they apply. As at 14 October 2026, the IET describes a transition to Amendment 4:2026, with the previous amendment set withdrawn on 15 October 2026. Other UK nations have their own building-control rules. Elsewhere, national implementations of IEC 60364 or applicable North American codes govern the work. CE or UKCA marking is not a substitute for confirming the correct device, installation method and any required inspection or certification.
Cloud, local APIs and what survives an outage
A monitor can continue sensing current when the internet fails yet still be unable to show a useful history. Separate four questions: does the hardware measure offline; can the homeowner access readings locally; are cumulative counters retained through power loss; and can missed data be recovered after Home Assistant reconnects? The answers differ by device and firmware. Do not assume that a local dashboard guarantees replay of every missed minute, or that a cloud application offers a reliable long-term export.
| System | Vendor-supported local data path | Offline history / recovery consideration | Home Assistant integration status |
|---|---|---|---|
| Vue 3 | No public or local API; cloud telemetry is the supported path | No local historical storage in the standard app workflow | Community cloud integration; not official vendor support |
| emonPi3 / emonTx6 | Local EmonCMS, MQTT, supported ESPHome path | Local logger can preserve history if installed and powered; confirm exact counter persistence and backups | Vendor-documented Home Assistant routes |
| CircuitSetup + ESPHome | ESPHome native local API or locally configured transport | Depends on firmware energy counters, persistence settings and HA Recorder availability | ESPHome component officially documented; assembled system remains DIY |
| Shelly Pro 3EM v2 | Local RPC, LAN, MQTT and official HA Shelly integration | Device has specified local logs; automatic backfill into HA is not guaranteed by mere device storage | Official HA integration, local push |
| PowerTag + Panel Server | Gateway Modbus TCP / supported industrial interfaces | Gateway retention and export depend on exact model and configuration | Modbus integration requires register mapping and commissioning |
If your requirement is reliable hourly or daily energy reporting for years, plan independent data retention. A small UPS for the Home Assistant host and network may reduce gaps but cannot guarantee complete readings through a power cut. Choose meters with trustworthy non-volatile cumulative energy registers, document their reset behaviour, and test how the selected integration handles reconnects and counter discontinuities. The official Home Assistant grid energy guide explains the compatible energy statistics needed for dashboards.
Avoid double counting: the board hierarchy matters
Suppose a home imports 24 kWh during a day. A three-phase feeder to a garage sub-board accounts for 7 kWh of that total, while two CTs on the garage EV charger and workshop circuits account for 5 kWh and 2 kWh. Adding 24 + 7 + 5 + 2 yields 38 kWh, which is false: the sub-board and branch values are already inside the grid total. Similarly, solar production is not identical to grid export; part of generation is consumed on site. Monitoring dashboards must respect measurement boundaries rather than summing every entity that has units of kWh.
Use a simple tree: grid boundary at the top; distribution-board feeder below; final circuits below that; individual plug loads below their final circuit where appropriate. Store separate signed import/export or distinct cumulative counters according to what the meter provides. On a grid-connected solar installation, choose the correct entities for grid import, grid export and generation. A CT measuring a bidirectional feeder may have a signed instantaneous power value but not necessarily two suitable cumulative import/export energy registers. Check the actual entities before placing them into Home Assistant Energy.
A useful commissioning metric is the residual: measured whole-home consumption minus the sum of non-overlapping monitored branches. A positive residual can represent unmonitored circuits, meter error or time-window mismatch; it is not automatically a mysterious appliance. A negative residual often signals overlap, wrong CT direction, an incorrect multiplier or inconsistent time bases. Compare stable operating periods and daily kWh, not merely instantaneous watts at two different sampling times.
Worked design: a twelve-circuit UK home with solar and an EV charger
Consider an illustrative three-phase house with twelve outgoing final circuits, a three-phase EV charger, a single-phase heat pump, a three-phase solar inverter and a garage sub-board. The owner wants to know whether the charger or heat pump drives evening peaks, whether solar is self-consumed and which groups dominate the base load. A naïve request for twelve CTs is under-specified because the three-phase charger and inverter each require phase-aware measurement, while the garage feeder may be a parent boundary rather than an independent additional consumption category.
| Priority | Measurement point | Indicative channel planning | Reason |
|---|---|---|---|
| 1 | Grid boundary, three-phase | Three main-phase measurements | Reliable import/export boundary; use dedicated main inputs where available |
| 2 | EV charger, three-phase | Three branch phase measurements | Identify charging demand and phase loading |
| 3 | Solar inverter output, three-phase | Three branch phase measurements | Measure generation rather than infer it from grid export |
| 4 | Heat pump, single-phase | One branch measurement | Isolate heating electricity from general consumption |
| 5 | Garage sub-board feeder | One or three depending on its actual feed | Useful hierarchy; do not add its downstream branches twice |
| 6 | Other major circuits | Remaining available channels | Choose immersion heater, cooker, sockets and standby groups by question value |
This illustration could require more than twelve measurement channels even though there are twelve outgoing protective devices. Conversely, if the grid meter and solar inverter already expose trustworthy local energy counters, you might avoid duplicating those boundaries with extra CTs. The design should start with available native data and add physical sensors only where a decision cannot otherwise be supported. On a smaller single-phase home, one mains CT plus eight branch CTs may be enough; on a three-phase property, six CT channels can disappear quickly into two three-phase measurement boundaries.
For this scenario, Vue 3 is attractive if the correct three-phase kit and cloud dependence are acceptable and sixteen branch inputs suffice after planning. emonPi3 with additional emonTx6 nodes offers a local-first route where six-channel increments make sense. CircuitSetup suits a dedicated technical maintainer who can validate a multi-board ESPHome build. A few Shelly units are sensible if the owner only needs the grid, solar and charger boundaries, not every circuit. The engineering answer is not always “buy the system with the highest CT count”.
A realistic all-in cost comparison without made-up prices
Online list prices are a poor basis for a permanent electrical installation: VAT, country distribution, selected CT bundle, compatible sensors, gateway, enclosure, delivery, inspection and labour all change the total. Rather than quote a transient product price as if it were universal, ask each supplier or electrician for the same completed scope. For an apples-to-apples comparison, specify twelve useful measurement channels, correct mains/phase coverage, data access for Home Assistant, five years of operation and a labelled handover.
| Cost item | Vue 3 | emonPi3/emonTx6 | CircuitSetup ESP32 | Shelly modular | PowerTag + Panel Server |
|---|---|---|---|---|---|
| Base monitoring hardware | Vue chassis | Six-channel nodes/base | Main board, ESP32 and any expansion | Several 2-/3-channel meters | Per-circuit sensors plus gateway |
| CTs / sensors | Main and branch bundle as ordered | Compatible CTs per channel | Compatible CTs and voltage references | Specified CTs with each unit | Compatible PowerTag sensor family |
| Power and protection | Specified voltage harness; extras for flex sensors | emonVS and suitable supply | Isolated supply, enclosure, sensing adapter | Meter supplies and appropriate protection | Panel Server supply and switchgear |
| Networking | 2.4 GHz Wi-Fi or Ethernet; internet needed | 433 MHz, Ethernet, MQTT, Wi-Fi path as configured | ESPHome Wi-Fi or supported Ethernet board | LAN/Wi-Fi per device | Industrial gateway network |
| Software/retention | Emporia cloud; community HA is unsupported | Local EmonCMS/MQTT/ESPHome | Self-maintained firmware and Recorder | Official HA integration; device logs | Vendor commissioning and register mapping |
| Installation effort | Many CTs and harnesses in one board | Several nodes, voltage and data path | Highest custom engineering burden | Repeated meter wiring and commissioning | Professional switchboard engineering |
For a cost decision, request an installed and commissioned quote with sensor count, a drawing showing the measurement boundaries, electrical certificate or equivalent local handover documentation, network setup, dashboard proof and who provides support. Ask whether a future replacement CT is a stocked spare, whether a gateway is locked to one ecosystem and whether the homeowner can export the raw data. Avoid estimating annual savings from the monitor alone: it reports consumption, but savings require an actual behavioural or control change.
Commissioning and acceptance tests worth paying for
A professional installer should leave more than a working app screenshot. The handover should include a current circuit schedule, CT/channel labels, product model and revision, software version, network address or access method, source of each voltage reference and a statement of which readings are billing-grade, advisory or approximate. A certified revenue meter and an advisory CT monitor are not interchangeable merely because both display kWh. Accuracy depends on the entire chain: CT range, power factor, voltage reference, phase assignment, sampling, scaling and the load being measured.
- Inventory: photograph and label each measurement point as part of the electrician’s documented work, with no homeowner exposure to live parts.
- Sanity check: confirm that a known load appears on the expected channel and that switching it off removes the expected contribution; do not rely on breaker names alone.
- Phase and sign: verify that import, export, solar production and three-phase power directions make physical sense under suitable operating conditions.
- Energy totals: compare non-overlapping channel sums against the mains boundary over the same interval and document expected unmonitored residual.
- Network failure: disconnect internet access in a controlled test and record which readings continue locally, then verify reconnection and counter continuity.
- Restart and retention: test Home Assistant restart, monitor reboot and backup restoration without losing the mapping or creating false kWh spikes.
- Handover: retain a schematic, configuration backup, firmware versions, warranty information and the procedure for safely replacing a sensor.
Do not attempt these tests by opening an energised consumer unit yourself. The user-facing checks are software comparisons and observations; electrical measurements, sensor repositioning and any testing inside the board belong to a suitably qualified professional. The acceptance criteria should be written into the quote so that “works with Home Assistant” means specific entities with correct units and reliable history, not simply an icon appearing on a dashboard.
Common mistakes that ruin an otherwise good installation
- Buying by headline channel count: sixteen ports may not cover sixteen independent three-phase loads, and three main ports are not three extra arbitrary branch ports.
- Assuming any CT works with any meter: voltage-output and current-output sensors, burdens, ratios and connectors are not interchangeable by appearance.
- Using the wrong phase reference: current alone is not enough for accurate active power when voltage phase or power factor is wrong.
- Ignoring panel volume: a CT that fits around a cable on the bench may not fit safely inside a packed distribution board.
- Calling a cloud bridge “local”: an unofficial integration can still rely on a remote vendor account and an internet connection.
- Adding a parent feeder to its children: this overstates consumption and creates misleading charts.
- Ignoring standby loads: low-load accuracy, no-load thresholds and CT range can matter more than headline accuracy for always-on circuits.
- Confusing power and energy: watts are an instantaneous rate; kilowatt-hours accumulate over time and must have consistent reset/retention semantics.
- Buying legacy accessories for current hardware: emonPi2 twelve-channel expansion details do not imply the emonPi3 has the same expansion board.
- Forgetting the owner’s access: a perfectly installed professional system is not useful to a homeowner if the only administrator login belongs to the contractor.
Recommendations by buyer type
| Buyer and constraint | Most sensible starting point | Why | When to choose differently |
|---|---|---|---|
| Homeowner wants 8–16 branch circuits, accepts cloud | Emporia Vue 3 with correct region/phase kit | Compact high channel density and app hierarchy | Cloud refusal, unusual service or CT fit rules it out |
| Homeowner wants local logging and 6–18+ points | emonPi3 plus emonTx6 nodes as required | Documented six-channel building blocks and local paths | Budget or node placement makes a simpler three-channel plan preferable |
| Engineer wants extensive custom local telemetry | CircuitSetup expandable six-channel ESP32 | Open firmware, documented ESPHome metering and expansion | No qualified installation plan or no maintainer |
| Only grid, PV and a few heavy circuits matter | Shelly Pro 3EM v2 / EM-50 mix | Good local integration without a large CT harness | Dense per-branch monitoring is the actual requirement |
| New professionally specified distribution board | PowerTag Energy with appropriate Panel Server | Designed for panel-level sensing and industrial integration | Existing consumer unit or small budget cannot justify gateway engineering |
Our overall choice is conditional, not a fabricated winner. For maximum out-of-the-box branch visibility, Vue 3 is compelling if its cloud dependency is acceptable. For a local-first owner prepared to configure hardware, current-generation OpenEnergyMonitor is the more straightforward supported system. CircuitSetup is the best fit for someone who actively wants an ESP32 engineering project and will maintain it. Shelly is often the better value when a small number of well-chosen measurement boundaries answers the actual question. A professional PowerTag installation makes sense when it is part of a wider panel design rather than an impulse retrofit.
Frequently asked questions
Can I measure eighteen circuits with one Emporia Vue 3?
Not as eighteen independent branch CT inputs on one unit: Vue 3 provides up to sixteen branch inputs and dedicated mains inputs. The manufacturer documents using multiple Vue units and distinguishes Combined Vues from nested sub-panels. Check whether your “eighteen circuits” includes grouped three-phase loads and whether every branch truly needs separate measurement before buying a second unit.
Can I use three Shelly Pro 3EM devices to get nine channels?
You can plan several separately installed three-channel devices for suitable measurement points, but each unit still needs its own correctly protected voltage connections, matched CTs, configuration and available space. The devices do not become a single nine-channel calibrated meter automatically. Confirm the exact phase arrangement and Home Assistant aggregation logic before purchasing.
Does a sixteen-channel monitor replace the electricity company’s meter?
No. A domestic monitoring system is primarily for insight and automation. It does not replace the utility’s approved meter or create legally accepted billing readings merely because its app shows kWh. Where submetering is intended for tenant billing or commercial cost allocation, specify the required metrology approvals and legal obligations separately.
Is a three-phase supply a problem for an ESP32 energy monitor?
It is manageable with appropriate hardware, isolated voltage references, phase mapping and calibration, but it is not a one-line ESPHome setting. CircuitSetup and OpenEnergyMonitor document multi-phase support; the precise implementation must follow the purchased board revision and be reviewed by someone competent in electrical metering. A single voltage reference applied indiscriminately to all three phases can give incorrect active power and direction.
Will Home Assistant automatically calculate each circuit’s monthly bill?
It can visualise energy data and tariffs when suitable entities and tariff logic are configured, but the bill also depends on standing charges, time-of-use periods, export arrangements, taxes and the utility’s billing method. A circuit’s kWh share is not automatically its share of the bill. Use the utility meter as the billing reference and treat branch monitoring as diagnostic.
What if my board is too small for CT clamps?
Do not force clamps into the enclosure. Ask an electrician to assess a safe measurement location, suitable alternative sensors, a dedicated adjacent enclosure or a redesigned board. Flexible main sensors can help some systems, but they have their own integrator and power requirements. In other cases, monitoring a few major feeders or using suitably specified inline meters is the better choice.
Official specifications and further reading
Product details and firmware change. The links below were checked against first-party documentation on 14 October 2026; recheck the exact model, local distributor and current technical sheet before ordering.
- Emporia Vue 3 product specification; CT and phase installation requirements; official developer-access limitations; more than sixteen circuits
- OpenEnergyMonitor emonPi3 and emonTx6 overview; Home Assistant data paths; older emonPi2 expansion context
- CircuitSetup expandable six-channel hardware documentation; ESPHome ATM90E32 component
- Shelly Pro 3EM 120A v2 specifications; Shelly Pro EM-50 specifications; official Home Assistant Shelly integration
- Schneider EcoStruxure Panel Server product range; supported-device and capacity guide
- Home Assistant electricity grid documentation; Home Assistant Modbus documentation; IET BS 7671 edition checker
For related, narrower decisions on this site, see DIN-rail Modbus energy meters, choosing CTs, pulse versus CT versus PZEM versus Modbus and ESP32 Modbus energy meter integration. Those guides cover individual technologies; the purpose of this article is to select and commission a whole-board multi-circuit architecture.