The Environmental Cost

Amount of additional carbon dioxide pumped into the atmosphere due to inefficient UK street-lights since 1st January this year:
Amount of additional carbon dioxide pumped into the atmosphere due to inefficient UK street-lights in the last 12 months:
This calculation assumes: there are 7.5 million streetlights in the UK; the number of streetlights is increasing by 3.4% per year (the same rate as light pollution, see CPRE); each streetlight has a 100W lamp; 1 kW hr produces 0.43kg of carbon dioxide pollution ( DEFRA's average figure, a mix of coal, gas, nuclear and renewables. e.g. Coal power stations produce 0.9kg/kWh, renewables produce no CO2 emission); that 30% of the light from a streetlight is wasted.

» Use our pollution calculator to find out how much carbon dioxide your lights produce.

Lighting is contributing to an increase in greenhouse gases - the UK causes 3% of global greenhouse gas emissions with only 1% of the world's population. To generate 1 kW hr of electricity uses about 1lb (0.5 kg) of coal and produces 2lb (0.9 kg) of carbon dioxide emissions. The chemical equation is: 4(-CH-)+5O2 -> 2H2O+4CO2+Energy, where CH=hydrocarbons=coal, O=oxygen, H=hydrogen & CO2=carbon dioxide (see also "How stuff works!" internet page.).

» The damage by home "Security" floodlights: Imagine a 500W light is on throughout the night all year: 500W * 4400 hrs/year * 2lb = 4,400 lb of CO2 emission per year! (equal to 312 stones/year, or 2,000 kg/year, or 2 tonnes per year!)
Fortunately, most floodlights are on an infra-red switch, so let us try a more realistic calculation taking this into account. However, most activate needlessly when, for example, a cat walks by, so let us assume that an average light is on for half an hour a night. There are 22 million dwellings in the UK, so if one in ten has a 500W floodlight, then there would be 2.2 million lights. If an average light is on for half an hour a night, then the national statistic is (2.2M x 500 W) x 0.5hr per night = 550,000 kW hr /night. Per year this must be multiplied by 365 = 200 million kWhr/ year. If one kWhr produces 0.9kg of C02, then some 180 million kg/yr of CO2 is produced as a by-product from producing the electricity needed to power domestic floodlights within the UK (80kg per 500W light per year, assuming the light is only on for 30 minutes per night).

» Home floodlights V's cars: A new diesel car would produce the same amount of pollution as a typical single 500W floodlight (80kg per year) in 550 km (150g CO2 per km), and an older car in about 170 km (figures from The Society of Motor Manufacturers and Traders limited). Lighting can be more polluting than most cars! That same diesel car would have to travel 1.2 billion km to produce the same amount of CO2 (180 million kg/yr) as that produced by all home floodlights in the UK! Or, 120,000 cars would have to travel 10,000 km per year. This means that the CO2 produced by domestic floodlights alone is statistically similar to that produced by the car usage of a city of 228,000 persons.
Ironically, park and ride car parks, built to cut road congestion and pollution, often remain floodlit when locked and empty all night, needlessly resulting in the production of the very greenhouse gasses which they aim to help reduce!

» The damage done by excessive street-lighting: There are 7.5 Million street lights in the UK, mean power 100W (ILE figures), that typically waste 15% of their light directly upwards, above the horizontal. Up to a further 15% of the light is spilt where it is not needed or not wanted. This amounts to about 131 kW hr of wasted energy per year per streetlight. Since a coal power station generates 0.9kg of CO2 per kWhr, a single streetlight generates about 120 kg per year of CO2 more than it needs to. Multiply this by the 7.5 Million streetlights in the UK, and a total of 830,000 tonnes of CO2 pollution is produced for the energy wasted by streetlights alone.
The total amount of power wasted above the horizontal is 110 MW, and if the further 15% of wasted light is included, some 220 MW is wasted in total per year. Since the mean generating capacity of a power large power station is 1Gwatt (1000 MegaWatts), and the typical running generation rate is 0.5 G Watt (PowerGen figures), this wasted electricity is equivalent to about half a power station.
If other sources of lighting are included (e.g. floodlights, etc.), this is a far greater number - over a 1 power station worth of energy, money and atmospheric pollution is wasted via lighting.

Related News items

November, 2005
The Guardian: Rome takes a dim view of wasted energy
"Rome is to dim its public lights to save savings of up to 40% could be made."

November, 2005
BBC News: Britain facing large energy gap
"Britain is facing a shortfall in energy supply in the near future, according to a major report.
"...the key to reducing that lies in renewables and energy efficiency."

June, 2005
BBC News: Emission cuts 'vital' for oceans: "Marine species are under threat from rising levels of acidity in the oceans, says the UK's Royal Society. Unless carbon dioxide emissions are cut, there could be irreversible damage to ecosystems, it warns. It is further evidence of the need to take action at next week's G8 summit, says working group chair, John Raven. "Failure to do so may mean that there is no place in the oceans of the future for many of the species and ecosystems that we know today," he said. "

May, 2005
The Guardian: Livingstone's Green Vision
"Mr Livingstone's aims include every development being built on previously used land and that "major developments should be zero carbon emission developments". He also wants all major developments to incorporate hydrogen or fuel cell technology and include gas pipes capable of carrying hydrogen. All insulation materials should be from natural materials. His vision even extends to improving the view of the stars in the night sky by insisting that outdoor lighting is designed to reduce the sodium glow above the city."

April, 13th, 2004
BBC News: Blair 'adrift' on the environment. "The government is being urged to do more to improve the long-term quality of life in Britain. The Sustainable Development Commission (SDC) says the government's "disappointing" efforts on climate change can be seen in the probable failure of the UK to meet its target for carbon emissions by 2010." (also see this related news story).