Most smart home light automations fail in the same way. The light switches off because you stopped moving for three minutes. You wave your arm at the sensor to convince it you're still there. Then it switches off again while you're on a video call.

A presence sensor eliminates this failure entirely. The TP-Link Tapo RE100 uses 60 GHz millimeter wave radar, the same technology in some premium security systems, to detect that a room is occupied whether the person is moving or not.

How mmWave Presence Detection Works

PIR sensors detect infrared radiation changes caused by movement. When you stop moving, a PIR sensor sees no change and eventually concludes the room is empty. mmWave radar works differently. It emits radio waves at 60 GHz and reads the reflections. A stationary human still reflects a breathing pattern, the chest expansion from breathing alone creates a measurable signal at this frequency.

The Tapo RE100's radar-based processing handles these reflections at 10 Hz, updating its presence state 10 times per second. It distinguishes between a person sitting still and an empty room because the micro-movements of breathing create a distinct signal pattern even when gross body movement stops. The result is smarter room automation that doesn't interrupt you.

This is why presence sensors are replacing PIR sensors in high-value applications like office lighting, hotel rooms, and now mainstream smart homes.

Detection Range and Coverage

Ceiling-mounted at 2.5 to 3 meters, the RE100 covers a 5-meter radius, approximately 78 square meters on a flat floor. That covers most single rooms, including open-plan living areas up to medium size.

Wall mounting is also supported but reduces coverage to a directional cone. At 1.5 to 2 meters height, the detection zone narrows to roughly 60 degrees horizontal and reaches about 6 meters forward. For narrow rooms like hallways or bedrooms where you want directional detection, wall mounting is the better configuration.

Sensitivity adjusts at three levels in the Tapo app. Low sensitivity is appropriate for a bedroom where you don't want a sleeping partner to trigger the sensor just by rolling over. High sensitivity catches subtle presence at the edge of the detection zone.

Connectivity and Hub Requirement

The RE100 connects via ZigBee 3.0, which requires a Tapo Hub, specifically the H200 or compatible Tapo hub. The hub connects to your router via ethernet and handles local processing.

This is a deliberate design choice rather than a limitation. ZigBee's low power consumption is why the RE100 runs on an internal rechargeable battery for up to 6 months between charges. A battery-powered Wi-Fi sensor would drain in weeks.

The Tapo Hub acts as the local processing layer. Automations defined in the Tapo app run on the hub, not in the cloud. If your internet goes down, the RE100 still detects presence and still triggers local automations. That's a meaningful reliability improvement over cloud-dependent sensors.

Setting Up Automations

The Tapo app's automation interface handles the most common presence scenarios without needing scripting. You define trigger conditions (room occupied, room clear) and actions (turn on/off devices, adjust brightness, change scene).

For a bedroom automation: RE100 detects room occupied after 10 PM, dim lights to 20%. RE100 detects room clear for 2 minutes, switch off all lights and lower thermostat. The two-minute delay prevents the lights from switching off while you step out briefly.

The delay between "presence detected" and "action triggered" is configurable in 30-second increments. The delay between "presence cleared" and "absence action" is separately configurable, usually set to 2 to 5 minutes to avoid false absences.

Home Assistant Integration

The RE100 integrates with Home Assistant via the Tapo integration in HACS. The sensor exposes a binary presence entity (on/off) plus sensitivity level. Home Assistant automations can use it in any condition or trigger.

For Home Assistant users who want more granular control, the Tapo integration supports local polling via the Tapo local API, which eliminates the cloud intermediary entirely. Response time for presence state updates is approximately 1 to 2 seconds via local polling.

Practical Applications

Beyond the obvious light control use case, the RE100 works well for:

Key Points

• Climate control: Only heat or cool a room when occupied. With a smart thermostat or smart plug controlling a space heater, you can drop room temperature by 2 to 3 degrees when nobody's there.
• Security awareness: Knowing which rooms are occupied in real time is useful context for security cameras and alarm systems, reducing false alerts when people are home but triggering them when rooms should be empty.
• Idle timeout for displays: Switch off a TV or monitor when you leave the room and nobody returns after five minutes.

The RE100 is one of the more capable presence sensors available at the Tapo price point. It isn't the cheapest option, but it's considerably more reliable than PIR for rooms where people sit still for extended periods.