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Presence sensor vs PIR

Updated: 23 October 2026

The light dies while you are still at the desk, and the fitting in the hall has done this for years without annoying anyone. Presence sensor vs PIR is that split. A PIR watches a change in heat, so it sees you walk and then loses you when you sit. A radar presence sensor is sold to keep the room occupied from smaller movement. The ten indoor rows on the [presence detector comparison](/hub/electronic-surveillance/presence-detector) are the radar side of that choice. This page also includes buying none of them. Peter F., editor for DIY & tools, did not run a detection test. A qualifying purchase can earn a commission at no extra cost to you.

The light dies while you are still at the desk, and the fitting in the hall has done this for years without annoying anyone. Presence sensor vs PIR is that split.

Our top picks

SONOFF SONOFF SNZB-06P24

Best overall

SONOFF SONOFF SNZB-06P24
8.1/10about £21.85
View offer
Meross Meross MS600

Best value

Meross Meross MS600
6.6/10about £29.99
View offer
SONOFF SONOFF SNZB-06P

Alternative

SONOFF SONOFF SNZB-06P
6.7/10about £24.96
View offer
On this page
  1. 1.What switches the light off
  2. 2.What the public test showed
  3. 3.When a PIR is the right buy
  4. 4.When these radar rows earn the socket
  5. 5.What you take on with radar

What switches the light off

A PIR looks for a warm body moving across its zones. When you sit, the heat stops changing, and the lamp goes off after the timeout. Waving an arm makes the PIR look healthy. That is the fault in a living room, and it is not a fault in a hall. Motion, for a PIR, is the walk. Presence, on these boxes, is the claim that a stationary person still counts. A longer timer does not create that second behaviour. The buying guide is where hub and power come in, after you accept that you need radar at all.

What the public test showed

Texas Instruments’ SSZT759 used their own boards, not any ASIN here. Their PIR detected walking and missed typing and breathing. Their millimetre-wave board detected walking and typing. At about 5.1 metres, only deep breathing still registered. That is one room, not a score for SONOFF, Meross or SwitchBot. SONOFF’s SNZB-06P24 page says still detection is best within about 3 metres, facing the unit, and that sleep is not reliable. Radar is for a seated person nearby. A hall does not need that result.
SONOFF SONOFF SNZB-06P24

Testsieger

SONOFF SONOFF SNZB-06P24
8.1/10about £21.85
View offer

When a PIR is the right buy

Keep the PIR on a hall, a landing, a loft ladder or a cupboard. You enter, the lamp comes on, you leave, it goes off. BREEAM’s knowledge base, a commercial scheme and not domestic law, accepts PIR in corridors because occupancy is transient. The same idea applies at home. Walking across the zones works better than walking straight at the sensor. Legrand’s guide, written for commercial 230 V fittings, makes that point. Do not buy a 24 GHz box to repair a bad angle. None of these ten ASINs is a hard-wired occupancy sensor. If the fitting already works for people who keep walking, leave it.

When these radar rows earn the socket

A desk or a sofa is where the PIR timeout becomes the complaint. UK reviews of the two SONOFF rows describe lights that stay on while someone sits, and also a state that sticks on Detected. Radar moves the failure. It does not delete it. One MS600 review says dogs were ignored. You still need the radio: a Zigbee coordinator, a Thread border router, or 2.4 GHz Wi-Fi and the MS600 lead. Who buys which row is the best presence sensor page.

What you take on with radar

Radar notices movement a PIR never asked about. Legrand says microwave sensors can see through glass, wood and plasterboard, and a UK review describes plants beyond a wooden wall holding an SNZB-06P occupied. Do not aim it at a party wall. The SNZB-06P is 5.8 GHz. Several rows print 24 GHz. The SwitchBot table prints 60 GHz. 24 GHz is not automatically better. Keep a PIR where people walk through. Use radar only where someone sits, on a radio you already run. A dual box is not a PIR with a longer timer.

Common questions

Why do the lights go off when I sit still?
The sensor is almost certainly a PIR. It saw the heat change when you walked in, and that change stopped when you sat. The timeout then does what it was set to do. Waving your arms creates a new change, so the lamp returns and the PIR looks fine. A longer timeout delays the dark. It does not detect the person who stays still.
Will mmWave see me reading or sleeping?
Reading, close to the sensor and facing it, is the case UK reviews of the SONOFF rows describe as an improvement on PIR. Sleep is weaker. SONOFF says the SNZB-06P24 cannot reliably detect a sleeping person, and the TI note, on a different board, already lost ordinary breathing at about 5.1 metres. Do not buy a radar row on a promise that it watches breathing in every room.
Is a PIR enough for a hall or landing?
Yes, if people only walk through. The lamp should come on as you enter and go off after you leave. A radar sensor can hold that lamp because of movement on the other side of the wall. Leave the PIR unless someone actually sits on the landing.
If radar sees through walls, is that a reason not to buy it?
It is a reason to aim it and to cut the range, not an automatic reason to keep a PIR on a sofa. Through-wall detection is how a seat sensor also sees the kitchen. If you cannot place it so the zone is the chair, and not the next room, a PIR with a timeout you accept may still be the calmer lamp.
Is a dual PIR-plus-radar box just a PIR with a longer timer?
No. The MS600, MS605, Lafaer and SwitchBot bullets describe two sensing methods, and they claim the PIR side helps ignore fans or pets. A longer timer only delays the off. Dual sensing can still stick on, or still clear while you sit. You buy it for the seat, not as a timer upgrade.

Related pages

Presence sensor false triggers

Presence detector

Best presence sensor UK for the hub you already have

Presence sensor buying guide: hub before gigahertz

How to set up a presence sensor on the hub you have

Sources

Public UK sources from the digest first, then the amazon.co.uk listings compared on this page. Prices and stars were taken on 21 October 2026.

  1. ICO, Home CCTV systems (retrieved 21 October 2026)
  2. GOV.UK, Electrical Equipment (Safety) Regulations 2016 (retrieved 21 October 2026)
  3. SI 2016/1101, Electrical Equipment (Safety) Regulations (retrieved 21 October 2026)
  4. Ofcom IR 2030 (retrieved 21 October 2026)
  5. GOV.UK, When you do not need building regulations approval (retrieved 21 October 2026)
  6. IET, Part P frequently asked questions (retrieved 21 October 2026)
  7. Texas Instruments SSZT759, mmWave and PIR on their board (retrieved 21 October 2026)
  8. amazon.co.uk, smart presence sensor (retrieved 21 October 2026)