Presence sensors for hotels: 4 technologies, which to pick, and why

There's a question that looks simple and turns out to be one of the hardest to get right in a hotel:

How do I know if a guest is inside a room?

Get it right, and you can do 4 things that change operations:

• Automate climate and lights so you don't waste energy when nobody's in
• Optimise housekeeping routes to avoid disturbing the guest
• Reduce unnecessary communications (no checkout alerts to guests still in)
• Detect presence when there shouldn't be anyone (security)

Get it wrong, and you create false positives (system thinks someone's in and nobody is, AC stays on) or worse, false negatives (thinks it's empty and housekeeping walks in at 11 AM with a guest sleeping).

In this guide we compare the 4 most used presence sensor technologies today, their pros and cons, and when each makes sense in a hotel.

Why the checkout button doesn't solve the whole problem

Before getting into sensors, worth clarifying: the checkout button (one of Controlá's products) solves part of the question, but not all of it.

The button tells you when the guest leaves (with 80% reliability, since that share presses it). But it doesn't tell you:

• If the guest went out for breakfast and will come back
• If they dropped things and re-entered
• If they're inside sleeping at an unusual hour

For those, you need a continuous presence sensor. That's where the 4 technologies come in.

Technology 1: PIR (Passive Infrared)

PIR sensors are the most common and cheapest. They detect heat changes in their field of view. If a person moves within range, the sensor registers it.

How it works: the sensor measures infrared radiation (heat) from the environment. When something warmer than the background (a person) enters the field, the sensor detects it.

Advantages:

• Very cheap (€5-20 per sensor)
• Low power consumption (battery lasts years)
• Mature tech, no surprises

Critical limitations for hotels:

• Doesn't detect static presence. If the guest is sleeping or sitting still reading, the sensor does NOT detect presence. It's the main problem for hotel use: a sleeping guest can be interpreted as absent.
• Sensitive to sudden temperature changes (heaters, open windows)
• Only detects within its field of view (typically 90-110°)

When to use in hotels: common areas, hallways, bathrooms (where people move). NOT recommended as sole sensor in rooms.

Technology 2: Microwave (motion radar)

Microwave sensors emit a radio frequency signal and measure how it changes when bouncing off moving objects (Doppler effect).

Advantages:

• Detect subtle movements (more sensitive than PIR)
• Pass through non-metallic surfaces (thin walls, glass)
• Work in any temperature condition

Limitations:

• May detect motion in adjacent rooms (false positives)
• Also don't detect static presence
• More expensive than PIR (€30-80 per sensor)
• Some countries require RF emission certification

When to use in hotels: long hallways, large areas (gym, lobby). Useful combined with other sensors, rarely as sole solution.

Technology 3: Ultrasound

Ultrasonic sensors emit sound waves above the human audible range and measure the echo bouncing off objects.

Advantages:

• Detect static presence (a sleeping guest IS detected, because waves bounce off the body)
• Very precise in enclosed spaces
• Not affected by ambient temperature

Limitations:

• Sensitive to ambient noise (other ultrasonic sources can interfere)
• Some animals (cats, dogs) perceive them — not a health issue, but can trigger reactions
• Medium cost (€40-100 per sensor)
• Limited coverage (typically 3-5 metres)

When to use in hotels: medium-sized rooms, where detecting static presence is critical. Good option to complement PIR.

Technology 4: mmWave (60 GHz)

mmWave sensors are the newest and most advanced. They use millimetre waves (60 GHz frequencies) to build a real-time "map" of the space.

How it works: they emit very high frequency signals that bounce off objects. By measuring the return pattern, the sensor can distinguish between a sleeping person, a sitting person, a fixed object (furniture), or nothing.

Advantages:

• Detect static presence with very high precision. Even a person sleeping in bed is clearly "present".
• Distinguish humans from objects (don't get confused by a fan or curtains moved by air)
• Pass through thin fabrics (a blanket, a towel) without losing detection
• Can even measure breathing rate (some models)
• Low visual profile (some are coin-sized)

Limitations:

• Cost: €80-200 per sensor, depending on model and supplier
• More complex setup (angle and detection zone calibration needed)
• Relatively new tech, less firmware maturity in some models

When to use in hotels: when detection quality matters more than cost. Premium rooms, suites, accommodations where a false positive is unacceptable.

The combination we recommend at Controlá

After testing all 4 technologies in real installations during 2024-2025, at Controlá we typically use this combination:

For standard hotel rooms:

• mmWave on the ceiling, pointing at the bed → detects continuous presence (including sleeping guest)
• Complementary PIR at the desk area → detects general motion

For short-term rentals:

• mmWave in the living/main area
• Door opening sensor on the main door → detects entry/exit

For common areas (hallways, lobby):

• PIR + microwave combined → balance between cost and precision

What the sensor CAN'T do (and why it matters)

There's an honest limitation no presence sensor solves:

It can't tell a registered guest from someone who shouldn't be there.

If the system detects presence in a room that should be empty (between two bookings), it can alert you. But it can't say if it's housekeeping, maintenance, or someone unauthorised.

For that you need to cross sensor data with other systems: the PMS (active booking?), the access control system (who opened the door?), or the housekeeping dashboard (anyone marked "cleaning in progress"?).

At Controlá we do exactly that: presence sensors are a piece of the puzzle, not the whole puzzle.

Common mistakes in hotel projects

Many try presence detection and get it wrong the same way. The three most common mistakes:

1. Using PIR alone in rooms

The guest complaint hits in the first week: the AC turned off while they were sleeping. PIR doesn't detect static presence. It's the number one source of complaints about badly executed hotel automation.

2. Trusting 100% on the sensor without redundancy

Any sensor can fail. A dying battery, interference, furniture blocking the field. Automation logic must have a fallback: if the sensor reports "empty" but the door hasn't opened in the last X hours, DON'T turn anything off.

3. Not calibrating per room

Furniture layout, room size, bed position, all affect how the sensor "sees". A generic calibration for 100 different rooms guarantees problems.

What does it cost to do it right?

A typical hotel room deployment with the mmWave + PIR combo costs between €80 and €150 in hardware + installation. Monthly subscription depends on total deployment size.

Payback considering energy savings and housekeeping improvements is usually between 8 and 18 months (Controlá internal data, 2025 installations).

Want presence sensors in your hotel?

If you manage a hotel or short-term rentals and want to:

• Automate climate and lights without disturbing the sleeping guest
• Optimise housekeeping routes with real-time data
• Detect unwanted presence in empty rooms

Book a 30-minute call. We'll help you pick the right combination for your case.

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This guide synthesises accumulated experience from Controlá installations during 2024-2025 in hotels and short-term rentals in Barcelona, Granada and Andalucía. Prices are indicative and depend on supplier and deployment volume. Payback figure comes from the Controlá internal log.