If you’ve ever forgotten wet laundry in the washing machine for 3 hours, you already understand the value of this automation.

Laundry machines and dryers have a very distinct power signature:

• Start of cycle: power jumps high
• During cycle: fluctuates (motor, heater, pump)
• End of cycle: drops to low standby power and stays there

By monitoring power, Home Assistant can reliably detect:

• Cycle started
• Cycle finished
• Send a phone notification
• Optionally flash a light, play a sound, or announce on a speaker

This guide shows two practical approaches:

1. PZEM-004T + ESP32 (wired power monitoring)
2. Smart plug / smart socket (no DIY electronics)

Both feed data into Home Assistant, where an automation uses a simple power curve logic.

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1. Which Method Should You Use?

Option A — PZEM + ESP32

Pros

• Accurate real-time power, voltage, current
• Works with almost any appliance circuit
• Cheap hardware

Cons

• Requires wiring inside a mains enclosure (safety)
• More DIY effort

Option B — Smart Plug (Shelly / TP-Link / Tuya / Zigbee)

Pros

• Easiest and safest
• Already supported in Home Assistant

Cons

• Some plugs struggle with high loads (dryers)
• Must choose a plug rated for your appliance current

Rule of thumb:

• Washing machine: smart plug is often fine (check amperage and surge rating)
• Dryer / big heater loads: safer to use dedicated monitoring or a properly rated device (e.g., Shelly EM / Shelly Pro EM / DIN meter)

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2. Power Behaviour of Washing Machines & Dryers

You need two thresholds:

• Running threshold: above this, the machine is “active”
  Example: > 10–30 W depending on appliance
• Finished threshold: below this for X minutes → cycle complete
  Example: < 3–8 W for 5 minutes

Standby power varies:

• Some machines sit at 1–3 W
• Others sit at 5–12 W (display, electronics)

So you must measure your appliance once, then set thresholds accordingly.

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METHOD 1 — ESP32 + PZEM-004T Power Monitoring

3. Hardware (PZEM)

Typical parts:

• ESP32 DevKit
• PZEM-004T v3 module
• Enclosure + terminals (recommended)
• Safe wiring to measure the appliance circuit

⚠️ Mains safety matters here. If you’re not confident with mains wiring, use the smart plug method instead.

3.1 PZEM Wiring (UART)

PZEM communicates by UART:

ESP32         PZEM-004T
5V     -----> VCC
GND    -----> GND
GPIO16 -----> RX
GPIO17 -----> TX

(Some PZEM boards use 5V logic on UART; v3 modules are usually okay, but confirm with your specific module.)

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4. ESPHome (Recommended) – PZEM Entities in Home Assistant

ESPHome makes this trivial.

esphome:
  name: esp32-laundry-power
  platform: ESP32
  board: esp32dev

wifi:
  ssid: "YOUR_WIFI"
  password: "YOUR_PASSWORD"

logger:
api:
ota:

uart:
  rx_pin: 16
  tx_pin: 17
  baud_rate: 9600

sensor:
  - platform: pzemac
    current:
      name: "Laundry Current"
    voltage:
      name: "Laundry Voltage"
    power:
      name: "Laundry Power"
      id: laundry_power
    energy:
      name: "Laundry Energy"
    frequency:
      name: "Laundry Frequency"
    power_factor:
      name: "Laundry Power Factor"
    update_interval: 5s

Home Assistant will now have sensor.laundry_power in watts.

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METHOD 2 — Smart Plug Power Monitoring

If you already have:

• Shelly Plug, Shelly Plus Plug
• TP-Link Kasa plug
• Zigbee plug with power monitoring
• Tuya plug (local integration preferred)

Home Assistant usually exposes something like:

• sensor.washing_machine_power
• sensor.dryer_power

You can use the exact same automation logic below.

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5. Home Assistant: “Cycle Finished” Detection Logic

We’ll create:

• A binary sensor representing “machine running”
• An automation that triggers when it goes from running → not running for a duration

This is more reliable than “power below X once” because it handles dips during the cycle.

5.1 Create a Template Binary Sensor: Machine Running

Add to Home Assistant YAML (or create in UI helpers if you prefer):

template:
  - binary_sensor:
      - name: "Washing Machine Running"
        state: >
          {{ states('sensor.laundry_power') | float(0) > 15 }}

Set the threshold (here 15 W) to match your machine.

For dryers you may use a higher threshold, but typically 15–30 W works.

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6. Automation: Notify When Cycle Finished

Trigger when the machine stops drawing power and stays stopped for a while (e.g. 5 minutes).

automation:
  - alias: "Laundry – Cycle Finished Notification"
    trigger:
      - platform: state
        entity_id: binary_sensor.washing_machine_running
        to: "off"
        for: "00:05:00"
    condition:
      # Optional: only notify if it was running recently
      - condition: template
        value_template: >
          {{ (as_timestamp(now()) - as_timestamp(states.binary_sensor.washing_machine_running.last_changed)) > 60 }}
    action:
      - service: notify.mobile_app
        data:
          title: "Laundry"
          message: "Washing cycle finished ✅ Time to unload!"

Why the “for: 5 minutes” matters

Washing machines can briefly drop power during a cycle (pump pauses, motor coasts).
The for: prevents false “finished” notifications.

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7. Avoid False Positives: Require “Cycle Started” First (Recommended)

For best reliability, track a cycle state:

• Create an input_boolean helper: input_boolean.washing_cycle_active

7.1 Cycle Start Automation

automation:
  - alias: "Laundry – Cycle Started"
    trigger:
      - platform: state
        entity_id: binary_sensor.washing_machine_running
        to: "on"
        for: "00:01:00"
    action:
      - service: input_boolean.turn_on
        target:
          entity_id: input_boolean.washing_cycle_active

This ensures it’s not a false blip.

7.2 Cycle Finished Automation (with cycle_active check)

  - alias: "Laundry – Cycle Finished (Reliable)"
    trigger:
      - platform: state
        entity_id: binary_sensor.washing_machine_running
        to: "off"
        for: "00:05:00"
    condition:
      - condition: state
        entity_id: input_boolean.washing_cycle_active
        state: "on"
    action:
      - service: notify.mobile_app
        data:
          title: "Laundry"
          message: "Washing cycle finished ✅"
      - service: input_boolean.turn_off
        target:
          entity_id: input_boolean.washing_cycle_active

This prevents notifications if the machine was never “in a cycle” in the first place.

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8. Extra Improvements

8.1 Different Messages for Washing Machine vs Dryer

If you monitor both, duplicate the logic with different thresholds.

8.2 Flash a Light or Play a Sound

Add actions like:

- service: light.turn_on
  target:
    entity_id: light.kitchen_light
  data:
    flash: short

or send to a speaker (Google / Sonos / HA Assist).

8.3 Show Status on Dashboard

Use a card:

type: entities
entities:
  - binary_sensor.washing_machine_running
  - sensor.laundry_power
  - input_boolean.washing_cycle_active

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9. Tuning Thresholds (The Part That Matters)

Before setting thresholds, watch your power sensor:

• Idle standby power (machine “off” but plugged in)
• Typical mid-cycle low points
• End-of-cycle standby behaviour

Start with:

• Running threshold: 15 W
• Finished threshold: “running” turns off when <15 W
• Finished for:: 5 minutes

Then adjust:

• If you get false finished alerts → increase the for: duration
• If it never triggers finished → reduce threshold slightly or check standby wattage

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Summary

A “cycle finished” detector is one of the best Home Assistant automations:

• Works with either PZEM + ESP32 or a smart plug
• Uses the machine’s power curve to reliably detect the end of a cycle
• Sends notifications so laundry doesn’t sit forgotten

Once tuned, it becomes one of those “how did I live without this?” automations—and it’s completely local and robust.