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Tasmota PZEM-004T Whole-House Energy Monitor

Monitor whole-house or circuit-level power consumption using a PZEM-004T energy meter with ESP8266 and Tasmota. Measures voltage, current, power, energy, frequency, and power factor via MQTT.

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Boards:ESP8266ESP32
Firmware:Tasmota
Use Cases:Energy MonitoringPower MonitoringSolar MonitoringHome AutomationCost Tracking
GitHubBlog Post

Tasmota PZEM-004T Whole-House Energy Monitor

Build a whole-house or circuit-level energy monitoring system using the PZEM-004T power meter module connected to an ESP8266 or ESP32 running Tasmota. Get real-time voltage, current, power, and cumulative energy readings via MQTT.

Why This Project

  • Know your energy usage — track exactly where electricity goes
  • Cost awareness — calculate actual cost of running each circuit
  • Solar monitoring — track solar panel production and grid consumption
  • Automation triggers — detect when appliances start/stop
  • Non-invasive — current transformer clamp, no wire cutting

Components Required

Component Purpose Est. Cost
PZEM-004T v3.0 module Energy measurement (80-260V, 0-100A) $8-12
Wemos D1 Mini (or Sonoff Basic) WiFi controller $3-5
Current transformer (CT clamp) Non-invasive current sensing Included with PZEM
1kΩ resistor Hardware mod for RX optocoupler $0.01

Total: ~$12-18

PZEM-004T v3.0 Specifications

  • Voltage range: 80-260V AC
  • Current range: 0-100A (via external CT clamp)
  • Power measurement: 0-23kW
  • Energy accumulation: 0-9999.99kWh
  • Frequency measurement: 45-65Hz
  • Power factor: 0.00-1.00
  • Communication: Modbus RTU over UART (9600 baud)

Hardware Modification

The PZEM-004T v3.0 requires a small modification for reliable UART communication:

Solder a 1kΩ resistor across the RX optocoupler (R4 position)

This mod allows the ESP8266's 3.3V TX signal to properly drive the optocoupler input. Without it, communication may be unreliable.

Wiring

PZEM-004T        Wemos D1 Mini
─────────        ─────────────
5V           →   5V
GND          →   GND
TX           →   GPIO14 (D5) — Tasmota RX
RX           →   GPIO12 (D6) — Tasmota TX

AC side:
L (Live)     →   Through CT clamp
AC Input L/N →   Mains voltage sense (parallel connection)

WARNING: This project involves mains voltage. Ensure all connections are properly insulated and installed by a qualified person.

Tasmota Setup

  1. Flash tasmota.bin (PZEM support is in the default build)
  2. Configuration → Configure Module
  3. Set GPIO14 to PZEM016 Rx
  4. Set GPIO12 to PZEM016 Tx
  5. Reboot — energy data appears on the dashboard

JSON Output

{
  "ENERGY": {
    "TotalStartTime": "2024-01-01T00:00:00",
    "Total": 1234.56,
    "Yesterday": 12.34,
    "Today": 5.67,
    "Power": 450,
    "ApparentPower": 480,
    "ReactivePower": 165,
    "Factor": 0.94,
    "Voltage": 232,
    "Current": 2.07,
    "Frequency": 50
  }
}

Multiple PZEM Modules

Monitor multiple circuits (up to 3 PZEM modules per ESP):

# Assign different Modbus addresses
# PZEM module 1: default address 0x01
# PZEM module 2: change to 0x02
# PZEM module 3: change to 0x03

Home Assistant Energy Dashboard

Tasmota PZEM data integrates directly with Home Assistant's Energy Dashboard for:

  • Real-time power consumption graphs
  • Daily/monthly energy totals
  • Cost tracking with utility rates
  • Solar production monitoring

Compatible Boards

  • Wemos D1 Mini — best for standalone energy monitor
  • Sonoff Basic — repurpose as energy monitor (solder PZEM to serial header)
  • ESP-01S + HW-655 relay — compact DIN-rail build
  • Any ESP32 board — for multiple PZEM modules or display integration

Resources

Blog Post

Project writeup & details

GitHub Repository

Source code & project files