LED lighting is efficient. LED lighting with occupancy controls is more efficient. But sensors aren’t magic—they need to be selected and placed correctly to deliver value.

Here’s what you need to know.

Why Occupancy Sensors Matter

Lights left on in empty spaces waste energy. Obvious, right? But the scale of waste is often underestimated.

Studies consistently show that commercial buildings have lights on in unoccupied spaces for 20-40% of operating hours. In some facilities, it’s higher.

Occupancy sensors address this by:

• Automatically switching lights off when spaces are vacant
• Optionally dimming to a lower level rather than full off
• Eliminating reliance on people remembering to switch lights off

The energy savings are real and measurable.

Sensor Technologies

Passive Infrared (PIR)

How it works: Detects heat signatures from moving objects (people). When a person moves within the detection zone, the sensor registers the temperature change.

Pros:

• Low cost
• Well-proven technology
• Works through most conditions
• No false triggers from non-human motion

Cons:

• Requires line of sight to occupant
• Sensitive to movement, not presence (a stationary person might not trigger it)
• Detection range drops at distance

Best for: Open areas, corridors, bathrooms, meeting rooms with active occupants.

Microwave (Doppler)

How it works: Emits microwave signals and detects reflections. Movement causes a Doppler shift in the reflected signal.

Pros:

• Detects through non-metallic materials (partitions, some walls)
• Very sensitive to small movements
• 360° detection without line of sight issues

Cons:

• More expensive than PIR
• Can detect movement beyond the intended space (through walls)
• May trigger on non-human movement (fans, curtains)

Best for: Offices with partitions, areas requiring high sensitivity, warehouses with racking.

Ultrasonic

How it works: Emits ultrasonic sound waves and detects changes in the pattern when objects move.

Pros:

• Very sensitive
• Works around obstacles
• Good for spaces with complex geometry

Cons:

• More expensive
• Air movement can cause false triggers
• Sound-absorbing materials reduce effectiveness

Best for: Restrooms, private offices, areas needing high sensitivity.

Dual Technology (PIR + Microwave)

How it works: Combines two technologies. Typically requires both to trigger for “on” and only one for continued “on.”

Pros:

• Reduces false-on triggers
• Maintains sensitivity for occupancy detection
• Best of both technologies

Cons:

• Most expensive option
• More complex

Best for: Areas where false triggers are problematic, high-value applications.

Mounting Options

Ceiling Mounted

Most common for commercial applications. Available in:

• Surface mount (visible housing on ceiling)
• Recessed mount (flush with ceiling tile)
• High-bay mount (for industrial spaces with high ceilings)

Detection patterns are typically circular or square from the mounting point.

Wall Mounted

Often combined with switch replacement. The sensor replaces the light switch.

Pros: Easy retrofit, occupant can override. Cons: Limited coverage angle, affected by furniture placement.

Fixture Integrated

Sensors built into the light fitting itself. Each fitting detects its own zone.

Pros: Simple installation (no separate sensor wiring), granular control. Cons: Higher cost per fitting, potentially excessive granularity.

Placement Strategy

Poor sensor placement is the most common cause of occupancy control failure. People complain that lights turn off while they’re still in the room.

Coverage Patterns

Understand the sensor’s detection pattern:

• PIR: Typically wedge or curtain pattern
• Microwave: Spherical pattern extending beyond the physical space
• Ceiling sensors: Circular cone projecting downward

Ensure coverage overlaps throughout the occupied space.

Avoid Dead Zones

Common dead zones:

• Areas behind furniture or partitions
• Corners not covered by sensor cone
• Areas too far from sensor (at detection range limits)

Walk the space and visualise where someone could be sitting or working. Is that position detected?

Consider Task Behaviour

Different spaces have different occupancy patterns:

Meeting rooms: People enter, sit, may be stationary for long periods. Need sensors that detect seated, minimal-movement occupants.

Corridors: People walk through briefly. Standard PIR works well.

Private offices: Single occupant, may be very still while reading or concentrating. High-sensitivity or dual-tech sensors appropriate.

Open offices: Multiple occupants, activity levels vary. Multiple sensors to ensure coverage.

Warehouses: Large areas, intermittent occupancy, often with tall racking. High-bay sensors with appropriate range.

Time Delays

Set appropriate hold times:

• Too short: Lights turn off while people are still there (annoying)
• Too long: Excessive energy waste during vacancy periods

Typical settings:

• Corridors and circulation: 5-10 minutes
• Meeting rooms: 15-20 minutes
• Private offices: 15-30 minutes
• Restrooms: 10-15 minutes

Adjust based on actual use patterns. Most systems allow tuning post-installation.

Dimming vs Switching

Switching: Lights go fully on when occupied, fully off when vacant.

Dimming: Lights reduce to a low level (e.g., 20%) when vacant, full level when occupied.

Dimming advantages:

• More comfortable transition (no sudden darkness)
• Maintains some light for safety/security
• Can extend LED life (always-on at low level vs on/off cycling)

Dimming disadvantages:

• Less energy savings than full off
• Requires dimmable fittings and drivers

For most commercial applications, dimming to a low standby level is preferable to full switching.

Integration Options

Standalone Sensors

Each sensor controls its own zone directly. Simple and cost-effective.

Networked Sensors

Sensors communicate with a central controller. Enables:

• Coordinated zone control
• Override and scheduling
• Energy monitoring and reporting
• Integration with BMS

More expensive but provides better data and flexibility.

Integrated with DALI

DALI-2 includes standardised sensor interfaces. Sensors communicate on the DALI bus, allowing coordinated control with other lighting functions.

Energy Savings Expectations

Realistic savings from occupancy sensors depend on:

• Baseline occupancy patterns (more vacancy = more savings)
• Sensor sensitivity and placement (well-designed = more savings)
• Time delay settings
• Dimming vs switching

Typical ranges:

• Private offices: 25-40% additional savings
• Open offices: 15-25% additional savings
• Meeting rooms: 30-50% additional savings
• Corridors: 20-35% additional savings
• Restrooms: 40-60% additional savings
• Warehouses: 30-50% additional savings

These are on top of LED conversion savings. So if LEDs save 60% and sensors save another 30%, the total is around 72% reduction from baseline.

Common Mistakes

Insufficient coverage: Don’t skimp on sensor quantity. Saving $200 on a sensor isn’t worth occupant complaints and lost savings.

Wrong technology for application: PIR in a private office where someone sits still won’t work well. Match technology to use case.

Too-short time delays: The number one complaint is “lights turn off while I’m working.” Start with longer delays; reduce if energy is the priority.

Ignoring commissioning: Sensors need aiming and adjustment. Don’t just install and leave.

No occupant education: People need to understand the system. “Wave your arm if lights dim” is better than “the lighting is broken.”

The Business Case

Adding occupancy sensors typically costs:

• Standalone sensors: $80-150 per sensor, plus installation
• Fixture-integrated: $30-60 premium per fitting

For a typical office floor:

• 100 LED panels with occupancy sensors integrated: $3,000-6,000 premium
• Annual savings (25% additional): $2,000-4,000
• Payback: 1-3 years

Combined with LED conversion rebates, occupancy controls often pay for themselves quickly.

The key is doing them well. Poorly implemented controls waste money and create frustration. Well-implemented controls deliver lasting value.

Get the design right. Commission properly. Adjust based on feedback.

It works.