Security lamps, porch lights and garden strings all spill into the dark around a home. UK planning guidance and lighting experts agree on a simple rule: light only where you need it, when you need it, and no more.
Pick a common type of outdoor light to see how it measures up against the five principles of responsible lighting. The bar shows how much light it is likely to spill into the night.
Based on DarkSky and the Illuminating Engineering Society's Five Principles and GOV.UK planning guidance on light pollution. General information only.
TWO NUMBERS WORTH KNOWING
Few dark skies, fewer caterpillars.
One figure on the sky above us, one on the insects below the lamps.
≈ 5%
People who saw a truly dark sky
Almost 4,000 people counted the stars they could see in Orion in February 2023. For just over half of them, severe light pollution obscured the night sky.
STAR COUNT 2023 · CPRE
52% fewer
Moth caterpillars in hedgerows under LEDs
Hedgerows under white LED streetlamps held 52% fewer caterpillars than unlit ones, against 41% fewer under yellow sodium lamps. The study sampled 55 sites in the Thames Valley.
STREETLIGHTS · UKCEH
Butterfly Conservation notes that the total abundance of moths in Britain has fallen by a third over the past 50 years. The study's authors say LEDs can be dimmed and filtered far more easily than sodium lamps.
FOUR THINGS TO TRY
Darker outside, no less safe.
These are mostly about where your existing lights point and when they are on, not about buying new ones.
Walk round after dark
Look at each outdoor light from the garden and the street. Ask what it is for and whether it shines past your boundary.
Tilt and shield
Point lamps down at the ground or path. A hood or shield stops light reaching the sky, the hedge and the neighbour's window.
Add a timer or sensor
Planning guidance suggests switching lights off when not needed, for example between midnight and 5am or 6am.
Choose warm and dim
Pick the lowest brightness that does the job and a warmer colour, with less of the blue-violet light that affects wildlife.
AI-generated image, not a photograph of a real person or place.
WHY DARKNESS MATTERS
The night shift needs the dark.
AI-generated image, not a photograph of a real person or place.
Moths, bats and migrating birds all rely on darkness. CPRE says artificial light confuses migrating birds, often fatally, and interrupts the feeding and breeding of pollinating insects and bats. The Bat Conservation Trust notes that the light-avoiding species include all of the UK's rarest bats.
People notice it too. In a CPRE survey, half of respondents said light through their bedroom window disrupted their sleep. In England, artificial light from premises can count as a statutory nuisance that councils must investigate.
Questions
Questions people ask
What counts as light pollution?
CPRE describes it as artificial light shining where it is neither wanted nor needed. It names three types: skyglow over towns, glare from overly bright lamps, and light intrusion spilling over a property boundary.
Are LED lights worse for wildlife?
In a UK field study, hedgerows under white LED streetlights had 52% fewer moth caterpillars than unlit hedgerows, compared with 41% fewer under sodium lamps. The authors add that LEDs are easier to dim and filter.
Will turning lights off make my home less safe?
The guidance is not about removing light that has a purpose. It asks for light that is aimed where it is needed and controlled, for example with a motion sensor, rather than left on all night.
What can I do about a neighbour's dazzling light?
A friendly word is often the first step. In England, artificial light from premises can be a statutory nuisance, and councils must investigate complaints about it.
What is the Star Count?
CPRE's annual citizen science survey asks people to count the stars they can see inside the constellation Orion. The 2023 count ran from 17 to 24 February and almost 4,000 people took part.
