Here is the short answer: a security light only works if it is mounted between 2.5 and 3 metres and aimed down and across the approach — not out at the horizon. Get that wrong and you have bought an expensive way to dazzle yourself, annoy next door and light up absolutely nothing a camera can use.
The mistake we see every week at the Villa Road counter has nothing to do with the light itself. Someone buys a 100W floodlight, bolts it under the soffit at four and a half metres because that is where the ladder reached, and points it straight out. The result: glare at head height, a driveway still in shadow, and a PIR that triggers on next door's cat and nothing else.
We have been selling exterior lighting to Birmingham's electricians from this counter since 1975. What follows is what we actually tell them.
1. Deterrence comes from contrast, not brightness
A burglar is not put off by lumens. He is put off by being visible — by being the only lit object in a dark space, with no shadow to stand in.
That is why aiming beats wattage. A 20W head pointed down across a driveway lights anyone crossing it from above — face and hands visible, nowhere unlit to stand. A 200W floodlight blasted outwards gives you a sheet of glare, a blown-out camera image, and a deep shadow directly under the unit, which is precisely where somebody stands to work on your door.
So the rule is: light the ground people walk on, not the air above it.
Which raises the question everyone gets wrong next — how much light you actually need.
2. How many watts you really need (it is far fewer than you think)
Domestic jobs almost never need more than 20–30W of LED. Here is the honest scale we work to at the counter:
- Back door, side passage, bin store: 10–20W. Anything more and you will be the house that lights up the whole street.
- Standard driveway, one or two cars: 20–30W.
- Long drive, double garage, small yard: 50W.
- Commercial yard, loading area, industrial unit: 100W and upwards — and at that point you are into a proper lighting layout, not a single head.
The Knightsbridge SL20CCTB sits exactly where most homes land. Twin adjustable heads mean you can cover the drive with one and the door with the other rather than compromising between them.
The SL20CCTB is a 20W twin-head unit with an integral PIR sensor, IP65 rated, in black, with adjustable CCT — so you can set the colour temperature on the unit rather than committing to it at the point of purchase.
Trade tip: if you are lighting for a camera as well as for the eye, set an adjustable-CCT head to its cooler position. Warm light flattens contrast on a sensor and makes number plates and faces harder to resolve; cooler light holds edge detail. If the light is purely for people walking to a back door, run it warm — it is far less hostile to live with.
3. PIR sensors: the three settings nobody adjusts
Every sensor-fitted security light leaves the factory on settings chosen to look impressive in a showroom, and almost nobody changes them. There are three, and all three matter:
Lux
This decides how dark it must be before the unit will trigger at all. Factory default is usually near-daylight, which means the light fires at four in the afternoon in November and you conclude the sensor is faulty. Wind it towards the moon symbol until it only works after proper dusk.
Time
How long it stays on after the last movement. Default is often ten minutes or more. For a driveway, one to two minutes is plenty and it stops the unit sitting on all evening because a hedge is moving.
Sensitivity and angle
The single biggest cause of nuisance triggering is not sensitivity — it is a sensor pointed at a road, a footpath or a neighbour's garden. PIR detects heat crossing its field of view, so it sees movement across the beam far better than movement towards it. Angle the sensor so that the approach path cuts across it.
The Knightsbridge FL16ABK gives you a 180° PIR on a twin-spot head, which is the right shape for a wall between two zones — drive on one side, gate on the other.
The FL16ABK is a 230V twin-spot LED security light rated IP55, using 2x8W CREE emitters for 1300 lumens, with a 180° PIR sensor and a black finish.
And when you want the sensor to be somebody else's problem, there is a simpler route.
4. Sensor built in, or sensor separate?
Our position after fifty years: for a single head on a single wall, buy the light with the sensor in it. Fewer joints, fewer cable entries, fewer things to go wrong in a Birmingham January.
Buy a separate sensor only when you are switching more than one luminaire from one detection point, or when the sensor needs to live somewhere the light cannot — round a corner, under an eave, at the top of a drive. That is a real scenario and it is worth the extra part, but it is not the common one.
The ESP NH30BS-CL is the straightforward integrated answer at the larger end of domestic.
The NH30BS-CL is a 30W LED security light with an integral sensor, in black. ESP also list the same body without the sensor if you are switching it from a plate or a separate detector — see the full floodlights and security lights range.
5. When you genuinely do need a floodlight
Yards, workshops and unit frontages are a different job. You are lighting an area to a level rather than triggering a pool at a door, and a sensor is often a nuisance — you want the area lit for the whole shift.
The Knightsbridge FLN50 is our most-shifted mid-size floodlight for exactly this.
The FLN50 is a 50W LED flood light rated IP65 in a die-cast aluminium body, producing 5430 lumens of cool white. Note it has no sensor — that is deliberate for area lighting. Step up again and the FLHL100 is a 100W unit producing 15500 lumens in cool white, rated IP66.
Trade tip: IP65 and IP66 are not interchangeable on an exposed elevation. Both resist jets, but IP66 is specified against powerful jets — which in practice is the difference between a sheltered wall and a gable end that takes horizontal rain off the Clent Hills all winter. On an exposed face, pay the extra.
6. The four mounting mistakes that cost people money
- Too high. Above roughly three metres the beam flattens, the pool spreads thin and the PIR starts looking over people's heads. Soffit height is convenient, not correct.
- Aimed outward. Lights the neighbours, blinds your camera, leaves a shadow under the unit.
- Above the camera, facing the same way. The camera meters on the brightest thing in frame — which is now your own light — and everything else goes black. Offset them.
- Straight into a window. Yours or theirs. Both end badly, and one of them ends with a complaint to the council.
Your Security Lighting, Summarised
| Job | Output | Sensor? | WME pick |
|---|---|---|---|
| Back door, passage, bins | 10–20W | Yes, integral | SL20CCTB |
| Two-zone wall (drive + gate) | 16W twin spot | Yes, 180° PIR | FL16ABK |
| Larger drive or frontage | 30W | Yes, integral | NH30BS-CL |
| Yard or workshop area light | 50W / 5430lm | No — runs on | FLN50 |
| Commercial yard, unit frontage | 100W / 15500lm | No — runs on | FLHL100 |
Where DIY stops
Replacing an existing exterior luminaire on an existing switched supply is generally within reach of a competent DIYer. Running a new circuit outdoors, or adding a new outdoor supply, is notifiable work under Part P and needs a registered electrician to certify it. Knowing where DIY stops is the mark of doing it properly, not a failure.
Expert Help in the West Midlands
We have been on Villa Road since 1975, and the counter is still the fastest way to get this right. Bring a photo of the wall and a rough measurement of the drive and we will tell you the wattage, the mounting height and the aiming angle in about ninety seconds — and we will tell you when the 20W is enough and the 50W is money wasted.
Browse the full floodlights and security lights range, the wider LED floodlights selection, or separate PIR and motion sensors if you are switching multiple heads. Trade accounts welcome. Get in touch if you would rather we specced it for you.
Frequently Asked Questions
How high should security lights be mounted?
Between 2.5 and 3 metres for domestic work. High enough to be out of easy reach, low enough that the beam still lands on the ground as a defined pool and the PIR sees people rather than looking over them.
Do security lights actually deter burglars?
Well-aimed ones do, because they remove the shadow to work in and make an intruder visible from the street. Badly aimed ones can make things worse by creating glare and a deep shadow directly beneath the unit.
Why does my PIR security light keep coming on for no reason?
Almost always the lux setting is too high, the sensor is angled at a road or footpath, or the time setting is so long that separate triggers run together. Adjust lux towards the moon symbol first — that fixes most cases.