Microwave Sensors vs Passive Infrared Sensors (PIR)

March 20, 2024

When searching for light fittings with sensors you’ll often find that there are two popular options. Microwave Sensors (MWS) and Passive Infrared Sensors (PIR). Both are designed to detect occupancy and trigger lighting accordingly, but they operate on different principles.

Both can actively trigger floodlights, high bays or general linear fittings to come on when they detect motion and movement. Both have their purpose in the world of lighting so stay tuned and we’ll go into further detail about what the differences are.

Understanding Microwave Sensors (MWS)

Microwave Sensors employ continuous waves to detect motion within a designated area. Unlike PIR sensors, which rely on heat signatures, MWS emit microwave signals and analyse the reflections to determine occupancy. This makes them highly sensitive to movement and capable of detecting even subtle changes in the environment. Additionally, MWS can penetrate certain materials such as glass, allowing for more versatile installation options.

Understanding Passive Infrared Sensors (PIR)

Passive Infrared Sensors, on the other hand, detect heat emitted by humans and animals. When a warm body enters the sensor’s field of view, it triggers the lighting system to activate. PIR sensors are known for their reliability and cost-effectiveness, making them a popular choice for various applications ranging from residential to commercial settings. However, they may be less effective in environments with fluctuating temperatures or where line-of-sight may be obstructed.

Key Differences Side By Side


  • MWS: Highly sensitive to motion, capable of detecting even minor movements.
  • PIR: Relies on heat signatures, making it less sensitive to non-thermal movements.

Installation Flexibility

  • MWS: Can penetrate certain materials like glass, offering more installation options.
  • PIR: Requires direct line-of-sight and may be affected by obstacles.

Environmental Factors

  • MWS: Less affected by temperature changes and air currents.
  • PIR: Susceptible to fluctuations in temperature, potentially leading to false triggers.

Application Scenarios

Office Buildings

In office environments where precise occupancy detection is crucial, Microwave Sensors offer an advantage. Their ability to detect subtle movements ensures that lighting is only activated when needed, optimising energy efficiency without sacrificing comfort.

Generally speaking, Microwave Sensors can also cover much further distances when compared to most Passive Infrared Sensors. This is something to take into consideration when specifying your lighting designs and security measures.


In warehouses with high ceilings and complex layouts, Passive Infrared Sensors provide a cost-effective solution if your light fittings are at lower levels (8m and under). While they may be less sensitive to minor movements, their reliability and wide coverage make them well-suited for large, open spaces where consistent lighting control is essential.

On the other hand, some warehouses may require full 360° triggers and motion detection through metal racking at much greater heights (8m and above). That’s where a Microwave Sensor is the better option.

Outdoor Areas

For outdoor lighting applications such as car parks or pathways, Microwave Sensors excel due to their ability to penetrate obstacles and withstand harsh weather conditions. This ensures reliable performance and enhanced security without compromising on energy efficiency.


In the debate between Microwave Sensors and Passive Infrared Sensors, there is no one-size-fits-all solution. Each type has its unique strengths and considerations, depending on the specific requirements of the application. By understanding the differences between MWS and PIR sensors, you can make an informed decision to maximise energy efficiency and enhance lighting control in your space.