Schemerlamp (fotocel)

Dusk-to-dawn vs motion sensor

	Dusk-to-dawn	Motion (PIR/radar)
On when	All night	When someone passes
Best for	Porch, façade lantern, “occupied” look	Path, garage, cellar
Energy	~4–8 W × 12 h/night	Very low average
Deterrent	Constant presence	Sudden light

Where to install

• Outdoor wall lantern with bulb sheltered — luminaire at least IP44.
• Window lamp for holiday presence simulation.
• Enclosed stair with no daylight: photocell may stay dark → bulb always on — wrong product.

Trap: the sensor “sees” its own light

If the cell catches spill from the bulb, it may think it is day and cycle off/on. Point the sensor at open sky or use a fitting that shields it.

Running cost (French regulated example)

5 W × 12 h/night ≈ 22 kWh/year. At the French regulated tariff 0.2001 € TTC/kWh (Base option from 1 August 2026 on the French market) that is about 4.40 €/year. UK: multiply kWh by your p/kWh unit rate.

Example product cited on FR site: Lucide ST64 filament dusk bulb 2200 K — Prijs op Amazon.nl bekijken. Solar alternative: Steinel XSolar.