Motion sensor or dusk sensor for outdoor lighting in winter

Why it matters in winter

Around the shortest day the sun in the Netherlands sets at about half past four and only rises after half past eight. Outdoor lighting that burns from dusk to daylight is then on for around sixteen hours a night. In June that is less than eight hours.

So in these months the way the lighting switches really counts. A floodlight at a loading dock or a wall light at the staff entrance does not need to burn at full output all night when nobody comes after closing time.

Three ways of switching

• Dusk sensor (daylight sensor): the light switches on when it gets dark and off at daylight. Suitable for lighting that must burn all night, such as a walkway or the entrance of a building used at night.
• Time switch or astronomical clock: switches at fixed times or at sunrise and sunset. Useful to switch the lighting off at, say, 23:00 when the site is closed.
• Motion sensor with daylight sensor: the light only switches on in the dark and only when someone enters the detection area. After a set time it switches off again. Suitable for entrances, loading docks, bicycle sheds and container areas.
• HI-LO (dims when vacant): an in-between option. The light burns at a low level all night and goes to full output on movement, so the spot is never completely dark.

Calculation: how much energy does a motion sensor save?

An example with a 50 W floodlight:

• Dusk sensor, on all night: 50 W x 16 hours = 0.8 kWh per night. Over 120 winter nights (November through February) that is 96 kWh.
• Motion sensor, on for 1 hour per night in total: 50 W x 1 hour = 0.05 kWh per night, 6 kWh over 120 nights.

At an electricity price of, for example, 0.30 euro per kWh that is 28.80 euro against 1.80 euro per floodlight per winter. How many hours the light burns in practice depends on how often someone passes and the run-on time you set. Use your own electricity price and burning hours; with ten floodlights on a site the difference adds up quickly.

Winter pitfalls with sensors

• Own light on the daylight sensor: if light from the luminaire itself or a neighbouring one falls on the sensor, it can keep switching on and off. Point the sensor away from the beam.
• Dusk level too high or too low: on a grey winter day a threshold set too high can switch the light on in the middle of the day. Set the threshold to the moment it really gets dark.
• Moving branches and traffic: a microwave sensor also sees movement behind thin walls and from branches or passing cars. A PIR sensor reacts to heat differences and is often calmer for a defined path or a door.
• Dirt, cobwebs and snow: a dirty sensor lens detects less well. Include cleaning in the annual check.
• Run-on time: too short and the light switches off while someone is still loading; too long and the benefit disappears. Start with a few minutes and adjust.

Which luminaires and sensors fit

• Compact FLUX floodlight with plug-in sensor: the 30 W with 4,000 lm in 2700K from 38.19 euro or the 50 W with 6,500 lm for 46.35 euro, IP66, also in 4000K and 5000K. The plug-in sensor is fitted in ten seconds: the PIR with daylight sensor for 12.99 euro or the microwave with daylight sensor for 16.35 euro.
• Wall lantern for an entrance or staff door: the Coach Lantern with LED package 600 and 4000K, IP44, with photocell for 85.68 euro, with PIR motion sensor for 94.01 euro or with HI-LO PIR for 101.15 euro. For a front door the Half Lantern with PIR, 6 metre range and 110 degree detection angle for 83.30 euro.
• Street lighting on the site: for luminaires in the VIA line the 40 W AstroDIM driver for 19.25 euro, which dims back automatically at night without a separate control cable.

All prices excl. VAT. Items from stock are delivered within 5 working days. More on choosing a floodlight in choosing a floodlight for site and facade and on lighting in the dark months in site lighting in the dark months.

Frequently asked questions