PIR Sensors vs. Microwaves: Which One to Choose?

How presence sensors work

Presence sensors automatically turn lighting on and off based on the detection of people in an area. The two dominant technologies are PIR (Passive InfraRed) and microwave (HF, High Frequency). They differ in physical principle, sensitivity, range, ability to detect through obstacles and false positive rate. The correct choice depends on the geometry of the environment, the type of occupancy and the level of automation required.

PIR sensors: principle, advantages and limitations

The PIR sensor is passive: it does not emit anything, but detects variations in infrared radiation (heat) produced by the movement of a body in its field of view. It is composed of a pyroelectric element and a segmented Fresnel lens that divides the area into detection zones. When a warm body crosses adjacent zones, the signal variation activates the sensor.

Advantages:

• Low cost (€5–25 for standard sensor)
• Very low stand-by consumption (0.3–0.5 W)
• Very low false positive rate if well oriented
• Available in many versions: recessed, wall, ceiling, outdoor IP65
• Long life (10+ years)

Limitations:

• Does not detect through glass, walls, furniture
• Requires direct line of sight
• Stationary people (sitting still, at desk) are not detected
• Works worse in warm environments (above 28 °C) where thermal contrast decreases
• Can give false positives near heat sources (radiators, vents, sunny windows)

Microwave sensors: principle, advantages and limitations

The microwave sensor is active: it emits electromagnetic waves typically at 5.8 GHz or 24 GHz and analyzes the frequency of the reflected echo. When a body moves in the area, the echo returns with a slightly altered frequency (Doppler effect) and the sensor activates the output. Sensitivity is adjustable via trimmer or DIP-switch.

Advantages:

• Very high sensitivity: detects minimal movements (hands typing, breathing)
• Works through glass, thin drywall, plastic, light wood
• Independent of ambient temperature
• Precise detection even in warm environments or with people seated for long periods
• Excellent for suspended ceilings and hidden installations

Limitations:

• Higher average cost (€15–60 per sensor)
• Higher stand-by consumption (0.8–1.5 W)
• False positives if installed near thin walls, fans, pipes with running water, dimmable lamps with electromagnetic interference
• Requires adjustment of sensitivity and detection range, otherwise it "sees" beyond the limits of the environment
• Not recommended next to EMI sources (routers, motors, inverters)

Comparative table PIR vs microwave

Recommended applications by environment

Each sensor is suitable for different uses and environments, let's see which ones.

PIR recommended for

• External entrances of houses, garages, gates
• Condominium stairs and stairwells
• Warehouses, archives, storage rooms
• External parking lots and yards
• Basements, taverns, technical rooms
• Perimeter security lighting

Microwave recommended for

• Bathrooms, showers, locker rooms (people often stationary or semi-hidden)
• Offices with desks and fixed workstations
• Long and narrow corridors
• Meeting rooms and conference rooms
• Suspended ceilings with plenum (hidden sensor)
• School classrooms, libraries, study rooms
• Retail areas where customers move slowly

Combined PIR + microwave sensors (dual-tech)

For professional applications, dual-tech sensors are increasingly common, which require simultaneous consent from both technologies to activate the output. Advantages: practically zero false positives, microwave sensitivity maintained, but need for PIR thermal coverage for confirmation. They are the standard in: healthcare corridors, high-end tertiary buildings, intrusion detection systems integrated with lighting, smart buildings with DALI-2 or KNX protocols.

Impact on energy savings

According to industry studies (Ledvance, Osram, Lighting Europe), the integration of presence sensors in environments with discontinuous occupancy brings typical savings of:

• Corridors and stairs: 50–70% on lighting consumption
• Bathrooms and locker rooms: 30–60%
• Open space offices: 20–40% (combined with daylight dimming)
• Warehouses: 40–80% (compared to always-on lighting)

The average payback of a Ledpoint sensorized system, in tertiary environments, is between 18 and 36 months depending on the electricity tariff and opening hours.

Reference standards

Microwave sensors must comply with EN 300 440 on short-range radio emissions, EN 62311 on exposure limits to electromagnetic fields and EN 61347-2-11 on auxiliary devices for lighting. UNI EN 15193 on energy performance of buildings (LENI – Lighting Energy Numeric Indicator) assigns a favorable correction factor to systems equipped with presence control, contributing to the building's energy class. All Ledpoint sensors are CE certified, RoHS compliant and compatible with DALI-2 / KNX systems where applicable.

Ledpoint case study

FAQ

What is the difference between PIR and microwave sensors?

The PIR (Passive InfraRed) sensor detects variations in heat emitted by moving bodies and is passive. The microwave sensor emits high-frequency electromagnetic waves and detects motion via the Doppler effect, even through thin obstacles like glass or drywall.

Which sensor is more sensitive to small movements?

The microwave sensor is significantly more sensitive: it detects minimal movements such as a seated person typing or breathing deeply. The PIR needs a larger movement of the body or limbs to activate and may not detect stationary people.

Do microwave sensors give more false positives?

Yes, they can be triggered by movements behind thin walls, glass panels or doors, and by nearby electromagnetic sources. For this reason they require careful adjustment of sensitivity and timer. The PIR is more selective because it only sees what is in the direct optical cone.

Which sensor consumes less energy?

The PIR has typically lower stand-by consumption (0.3–0.5 W) compared to microwave (0.8–1.5 W) because it is passive. The difference is marginal on the total system, but relevant in installations with hundreds of sensors.

Which one to choose for a bathroom or locker room?

For bathrooms, showers, locker rooms and environments with people often stationary or semi-hidden, microwave is preferable because it detects small movements and works through thin partition walls. PIR risks turning off the light with a stationary user.

Can I use a PIR sensor outdoors?

Yes, there are PIRs with IP44–IP65 rating for outdoors. They should be oriented away from heat sources (vents, streetlights) and protected from wind and moving leaves, which can cause false detections. For entrances and perimeters, PIR remains the most widespread standard.

Are microwave sensors dangerous to health?

No. They emit powers in the order of 0.2–1 mW, thousands of times lower than a smartphone or Wi-Fi router, and well below the limits of European standards EN 300 440 and EN 62311. There are no documented risks for prolonged exposure.

PIR vs microwave sensors: a functional choice.

The choice between PIR and microwave is not between a "good" sensor and a "bad" sensor but between two tools with different strengths.

We can therefore conclude by indicating the Ledpoint practical rule:

• PIR sensor where you enter and exit (entrances, stairs, warehouses, outdoors)
• Microwave sensor where you stay still (bathrooms, offices, meeting rooms, low-traffic corridors)
• Dual-tech sensor where zero false positives is essential (healthcare, high-end tertiary, smart building).

Always combined with fine adjustment of sensitivity, timer and when possible daylight dimming to maximize savings.