Where should a security light go, and how bright should it be?

Light helps because it removes cover and makes anything happening visible from a window or a passing car. It stops helping the moment it is so bright that everything outside the beam is a black void and anyone looking towards it is dazzled. The aim, not the wattage, is what does the work.

Safety

What you'll need

• A PIR floodlight of modest output
• A registered electrician for any new circuit
• Ladder or tower with a stand-off
• Voltage tester

Step by step

1. Decide what each light is for.Lighting a path so you can walk it, lighting an approach so movement is visible from indoors, or lighting a dark side alley. They want different fittings and different aims, and combining all three in one floodlight does none of them well.
2. Put lights on the approaches, not on the whole house.The front path, the side access, the back door and the shed. A wall washed with light everywhere just creates glare and drowns out the movement you want to notice.
3. Mount at 2.5 to 3 metres.High enough to cast a wide pool and be out of easy reach; low enough that the PIR sees across the approach rather than straight down. Above about 4 metres the detection pattern spreads too thin to trigger reliably.
4. Aim the beam at the ground you care about.Tilt down so the brightest part of the pool lands on the path a couple of metres out. If you can see the lamp itself from the pavement or from a neighbour's window, it is aimed too high.
5. Choose a modest output.Around 800 to 1500 lumens covers a domestic path or drive. Higher outputs are for yards and car parks and they cause hard shadows next to the beam that hide more than the light reveals.
6. Use a warm-white lamp.Around 3000K. Very cold blue-white light is harsher, worse for wildlife, more disturbing to neighbours and no more useful for seeing.
7. Set the PIR to see across the approach, not along it.Passive infrared detects movement across its field far better than movement directly towards it. Aim the sensor so someone walks across its view and it will trigger much earlier.
8. Mask the sensor away from the road and the neighbour.Most PIRs have a sliding shield or you can use a strip of tape on the lens. Removing the pavement and next door's drive from the detection field prevents most nuisance triggering.
9. Set a short on-time.One to two minutes is plenty. Long timers turn a security light into a floodlit garden, which is exactly the complaint neighbours make.
10. Check it after dark from three positions.From your own window, from the pavement, and from the neighbour's boundary. If it dazzles from any of them, tilt it down further or fit a baffle.
11. Think about wildlife and light spill.Continuous outdoor lighting disrupts bats, moths and hedgehogs and is bad practice. Motion-activated with a short timer, aimed down, is much better than a dusk-to-dawn floodlight.

Tips

• A dim light left on low all night at a door is often more useful than a bright one that flashes on — eyes stay adapted and you can actually see.
• Solar PIR lights have become genuinely usable for a side gate or a shed and involve no notifiable work at all.
• If the light is meant to help a camera, put it beside or behind the camera, never in its field of view.

Common mistakes

• Fitting the brightest floodlight available — Glare contracts your pupils and turns everything outside the beam into blackness. It also generates neighbour complaints, which is how security lights end up disconnected.
• Aiming the fitting horizontally — A horizontal beam lights the neighbourhood, dazzles anyone approaching and puts almost no light on the ground you are trying to see.

If it doesn't work

Questions people ask