Presence Sensor vs Motion Sensor: What Actually Changes in Your Home

Answer up front — A motion sensor answers "is something moving?" and a presence sensor answers "is anyone here?". A passive infrared motion sensor detects changes in heat across its field of view, so a person sitting still becomes invisible to it; mmWave radar detects the micro-movements of a breathing body, so it can still know the room is occupied. That difference decides whether an automation works when you are reading on the sofa or asleep in bed. It is also why presence sensors cost more and mount higher. One important caution up front: Aqara's FP400 spatial sensor was released globally on 16 September 2026 and its listed retail channels do not include Malaysia, so availability here must be confirmed.

Every smart home owner has hit this: the hallway light switched itself off while you were standing still, or the bedroom aircon switched off in the middle of the night. The usual explanation is a fault. It usually is not a fault. It is a motion sensor doing exactly what a motion sensor does, and the gap between that behaviour and what you wanted is the entire subject of this article.

The difference in one sentence

Motion sensors detect change. Presence sensors detect occupancy.

A passive infrared sensor, or PIR, is a passive device: it sits behind a plastic lens, splits the infrared light coming from the room into zones, and watches for a difference between the zones. Warm something moving across a boundary and the pattern changes, so it triggers. Stand still and the pattern stops changing, so after its timeout it decides the room is empty. A cat, a curtain in the breeze and a person walking past all look the same to it, because from its point of view they are all just moving heat.

A mmWave radar sensor sends out a low-power radio signal in the 60 GHz band and measures how the reflected signal changes. A breathing body produces a small but continuous movement — the chest rises, micro-movements persist. That is enough to distinguish "a person is sitting very still" from "the room is empty", and it is why presence sensing is the more accurate of the two.

What that changes in practice, room by room

The pattern is worth stating plainly: motion sensing is still the right tool for corridors and staircases, where passing through is the event. Presence sensing earns its cost in the rooms people sit or sleep in — which, in a Malaysian home, is most of them.

How mmWave presence sensing actually works

Aqara's Spatial Multi-Sensor FP400 is the most complete public example of this technology in Aqara's range. It was announced at CES 2026 and released on 16 September 2026. In summary, from Aqara's own product material:

• 60 GHz mmWave radar with an upgraded AI sensing algorithm
• Tracks the real-time position of up to 10 people simultaneously
• Verified coverage up to 10 m depth × 8 m width, with a 120° wide field of view
• A room can be divided into up to 8 zones
• Distinguishes posture — standing, sitting, lying down
• No camera. Aqara's stated privacy argument is precisely this: it senses presence without producing images
• IPX5 rated; operating temperature −10 °C to 50 °C; operating humidity 0–95% RH, no condensation
• Side, corner and ceiling mounting; 64 × 64 × 29.5 mm; USB-C powered
• Thread and Zigbee dual protocol

The no-camera point deserves emphasis for Malaysian homes, particularly for bedrooms and children's rooms. Presence sensing answers "is someone there" without generating a picture of anyone. It is a genuinely different privacy posture from a camera-based occupancy solution, and it is the reason this class of sensor is credible for private rooms.

Availability in Malaysia — confirm with us. Do not assume it is on the shelf at a local store. Aqara announced global availability on 16 September 2026 and listed Aqara's own store plus Amazon in Belgium, Canada, France, Germany, Ireland, Italy, the Netherlands, Poland, Spain, the UK and the US. Malaysia was not in that list, and a scan of local marketplace listings in September 2026 found no FP400. Treat it as something to ask about, not something to go and buy.

The coverage geometry, exactly

Presence sensors need height, and the numbers matter if you have a high ceiling or a low one.

• Recommended installation height: 3–4 m
• At a 3 m mounting height, the area covered directly below the sensor is up to 5 × 6 m for motion and 4 × 5 m for presence
• Verified detection reach extends to 10 m depth and 8 m width overall, within a 120° field of view

That geometry is not cosmetic. In a landed house with a high-ceilinged living room, ceiling mounting at 3 m or above is what makes a single sensor viable. In a condominium with a 2.7 m ceiling, the same maths does not work the same way — the sensor sits closer to head height, its 120° field spreads much wider across a short distance, and you may need more devices or a different mounting position. We would rather tell you that during a survey than after installation.

Our installation guide for presence sensors covers placement in detail, and our hub compatibility matrix covers which hubs will actually run one.

The limitation nobody writes down

Here is the detail that matters most if you are planning to put a presence sensor into Apple Home, Home Assistant or another third-party platform, and it is the part most competitor articles omit.

When the FP400 is integrated over Thread, it exposes only 1 overall presence sensor and 1 illuminance sensor. You lose the per-person tracking, the zone data and the posture distinction — the three capabilities that made it worth considering in the first place. It still knows whether the room is occupied. It stops knowing who, where and in what posture.

Two related requirements come with that. An Aqara hub is essential when integrating the FP400 into third-party Matter platforms in Zigbee mode. And using it in a third-party Matter platform requires a Matter Controller and a pre-configured third-party Thread Border Router supported by the target ecosystem.

Which means the hub choice decides how much of the sensor you actually get. In the native Aqara path on a supported hub, you get zones, posture and per-person tracking. In a third-party Thread path, you get presence and illuminance only. That is not a minor difference and it should be part of the purchase decision, not discovered afterwards.

There is also a hard hub floor. To experience FP400 features you need an M3, M100 or M200 hub running at least firmware 4.5.70, and compatibility varies by model, region and firmware.

That last row is worth pausing on. If you already own a Hub M2 or an older G3, an FP400 will not work on it, and no firmware update will change that.

What this page does not claim

• It does not claim the FP400 or FP400 Pro is available to buy in Malaysia. Confirm with us.
• It does not give a price for the FP400, the FP400 Pro, the FP300, the Thermostat Hub W200 or the Hub M3. Confirm with us.
• It does not claim fall detection, medical monitoring or any clinical function.
• It does not claim presence sensing is right for every room. Corridors do not need it.