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OpenEnergyMonitor emonTx6 vs ABB B21 312-100

Install fit
Phase support Single-phase and three-phase four-wire AC; three-phase three-wire is unsupported. Single-phase, 220-240 V AC, 50/60 Hz.
Installation Wall-mounted node with external emonVs voltage/power sensor and clip-on CTs; competent panel installation required. Indoor 2-module 35 mm DIN-rail direct-connected installation; IP20 meter for qualified-electrician panel wiring.
Measurement Six-channel continuous-sampling CT measurement of real/reactive power and cumulative energy. Direct-connected single-phase active/reactive energy and electrical-parameter metering with separate import/export registers.
Max current 200 A 65 A
Meter fit
Accuracy class Unknown MID Class B / IEC Class 1 active energy; Class 2 reactive energy.
Current sensing Six inputs for 333 mV voltage-output CTs; official 20 A, 50 A, 100 A, and 200 A options. Built-in direct current path rated 0.25-5(65) A; no external current transformer required.
Monitoring
Protocol 433.92 MHz radio / USB-C serial / optional emonWiFi Wi-Fi and MQTT RS-485 Modbus RTU / EQ Bus / S0 pulse outputs
Local API Yes Yes
Cloud dependency No vendor cloud required; local radio, USB serial, optional emonWiFi, EmonCMS, ESPHome, Home Assistant and MQTT paths. EmonCMS.org is optional. No vendor cloud required; measurements are read locally over RS-485 Modbus RTU, EQ Bus, S0 pulse, or the front display.
Home Assistant Yes Yes
Solar fit
Solar import/export Yes Yes
Buying context
Price range GBP 198.67 inc. VAT / GBP 165.56 ex. VAT before option changes EUR 420 gross list price from ABB Netherlands; net price, tax, stock, and regional distributor pricing vary.
Availability UK official shop; international shipping varies by destination, tax, radio rules and electrical suitability. ABB global product and distributor channels; current Netherlands official channel listing verified, with regional stock and certifications varying.
Source check
Last verified Oct 13, 2026 Oct 14, 2026
Product page Official page Official page
Documentation Official docs Official docs
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