Sonoff
Sonoff SNZB-04P Zigbee Door & Window Sensor
- Zigbee
Verified September 2026
The cheapest contact sensor we would actually fit to every window: smaller than the old SNZB-04, a tamper alert the Aqara P2 lacks at this price, and unobtrusive enough on a white frame that it doesn't scream 'smart home' to visitors. Sonoff rates the CR2477 coin cell at around five years, realistic if the door isn't opened dozens of times a day. Keep the sensor-to-magnet gap under 20mm when closed — go wider and it'll report false 'open' states. Pairs directly with Zigbee2MQTT or ZHA — ignore the 'Sonoff bridge required' box copy.
In Home Assistant
| Control | Type | What it does |
|---|---|---|
| Contact | Binary sensor | Open/closed state of the door or window. |
| Battery | Sensor (%) | Remaining battery as a percentage. |
| Battery low | Binary sensor | Flags when the CR2032 is almost empty. |
| Tamper | Binary sensor | True when the sensor has been pried off its mount — reliable on Zigbee2MQTT, unreliable without a custom quirk on ZHA. |
| Voltage | Sensor (mV) | Raw battery voltage, more granular than the percentage figure for judging real remaining capacity. |
Zigbee2MQTT exposes contact, battery percentage, battery_low, tamper, and raw battery voltage in millivolts, but tamper support genuinely differs by integration: ZHA users report the plunger switch produces no events at all until a custom quirk is applied, whereas Zigbee2MQTT surfaces tamper correctly as its own boolean. Even under Zigbee2MQTT, clearing a triggered tamper state has been reported to throw a cluster error and leave the sensor stuck reporting tampered. Because raw voltage is published alongside the percentage, a more reliable low-battery automation trips on voltage crossing roughly 2.5V rather than trusting the coarse, non-linear percentage curve CR2032s show near end-of-life.
Specs
- size
- Compact, surface-mount with adhesive
- power
- CR2477 (3V), ~5 years typical battery life
- extras
- Tamper alert
- dimensions
- Sensor 50.5 x 32 x 21.9mm, magnet 27 x 12 x 12.4mm, 33g total
- sensor type
- Contact (door/window)
- detection gap
- Sensor-to-magnet gap must be ≤20mm when closed