Energy & Power Monitoring

The 2026 home-energy stack is no longer "buy a Sense and pray to its cloud." It's a circuit-level CT-based meter publishing to MQTT plus per-device smart plugs for the loads that matter. Cheap, local, accurate enough.

For the hub above this layer see Smart Home Hubs; for solar / EV / inverter dashboards see EV & Solar; for the underlying ESP firmware see IoT Firmware Platforms.

Whole-house / circuit-level

• ★ Shelly Pro 3EM — DIN-rail 3-phase meter; CT clamps per phase; gigabit Ethernet + Wi-Fi; MQTT, HTTP, Modbus in firmware. The default for new installs in the EU; great in NA single-phase if you understand the wiring.
• ★ Shelly EM / Shelly EM Plus — 1-or-2 channel CT-based meter; older sibling; works fine.
• ★ IoTaWatt — 14-channel CT-based whole-home monitor; open source; built around a NodeMCU + ADC; influxdb/mqtt out. Cult favorite in the US for its accuracy.
  • https://github.com/boulderlabs/IoTaWatt
• Emporia Vue Gen 2 / Gen 3 — 16-channel CT meter; closed firmware but flashable to vuegraf / ESPHome custom firmware on Gen 2 (ESP32 inside) for fully local readings. Cheaper than IoTaWatt; "is it reliable" depends on your tolerance for unsupported flashes.
• Sense — the brand that made circuit-disaggregation famous; closed cloud; don't pick for HA-first homes.
• Schneider Wiser Energy / Eyedro — closed; integrate via cloud APIs only.

Per-circuit / sub-panel

• Brultech GreenEye Monitor (GEM) — 32-channel; commercial; pricey; the "I want every breaker monitored" answer.
• OpenEnergyMonitor (emonPi / emonTx) — UK; open hardware; older; well-documented.
• ESPHome with split-core CTs + ADS1115 — DIY; pair a $20 ESP32 with current transformers; great for "monitor my workshop sub-panel."

Per-device (smart plugs)

• ★ Shelly Plus Plug S / Plug US / 1PM / 2PM — Wi-Fi smart plug + power monitoring; MQTT + HTTP + Bluetooth provisioning; the new default. Local-only mode supported.
• ★ ESPHome with a PZEM-004T — the bring-your-own-plug option; PZEM gives accurate voltage / current / power / energy via UART; ESPHome wraps it. Use for hardwired in-wall installs.
• Tasmota smart plugs — Athom, Sonoff S31, Athom Plus 16A: pre-flashed Tasmota. Same idea, web UI on the device.
• Aqara Zigbee plugs — pair via Z2M / ZHA; less accurate than dedicated meters but fine for "is the dryer running."
• Kasa / TP-Link HS110 / KP115 / KP125M — closed firmware; have HA integration; cheap.

UK / smart-meter specific

• ★ Hildebrand IHD-CAD MQTT Glow Stick — CAD-attached device that pulls SMETS2 readings off the In-Home Display protocol and publishes to MQTT. The clean way to get UK smart-meter consumption into HA. £70.
  • https://shop.glowmarkt.com
• Octopus Energy / OVO API integrations — for tariff / agile pricing; HA has community integrations.

Inverter / solar / battery monitoring

See EV & Solar for the full story (SolarAssistant, EVCC, Victron, Growatt, etc.).

Long-term storage / dashboards

• ★ HA's Energy Dashboard — built into Home Assistant; ingests power + utility cost meters and shows daily / monthly / yearly. The first thing to set up after your meter is publishing.
• ★ InfluxDB / TimescaleDB + Grafana — for retention beyond HA's recorder window. See Time Series Databases and Prometheus Stack.
• Emoncms — the OpenEnergyMonitor dashboard; influx-style storage tuned for energy.

Practical guidance

• ★ Get the polarity right on CT clamps. If a circuit shows negative power when the load is running, flip the clamp.
• ★ Calibrate against a Kill-A-Watt or your utility's smart meter. Cheap CTs lie by 5-15 % until calibrated.
• Don't measure 240 V loads with a single 120 V CT. You need either a true 240 V meter or careful math.
• Solid-state vs. mechanical relays in smart plugs: for inductive loads (motors, vacuums), prefer relay-based plugs to avoid welding the SSR.
• 3-phase EU homes need a Pro 3EM, not three Shelly EMs. Phase angles matter.
• HA Energy Dashboard requires kWh-cumulative entities, not instantaneous watts. Most meters expose both; pick the right ones.

Pick this if…

• Default whole-home (US / single-phase): IoTaWatt or Emporia Vue + custom firmware.
• Default whole-home (EU / 3-phase): Shelly Pro 3EM.
• Per-device smart plug: Shelly Plus Plug S; or pre-flashed Tasmota Athom.
• DIY in-panel measurement: ESPHome + PZEM-004T.
• UK smart meter: Hildebrand Glow Stick.
• Long-term graphs: HA Energy Dashboard + InfluxDB + Grafana.