How to reduce your ecological impact at the flick of a switch

Over the course of one year, leaving on just one light overnight costs around £24 and accounts for as much greenhouse gas as driving 335 miles—that's the distance from Cambridge to Paris.

Neglecting to turn off lights (as well as other electrical appliances) can produce thousands of pounds of unnecessary carbon dioxide emissions. In fact, the Energy Saving Trust estimates that turning off unneeded lights could remove 171kg of CO2 emissions per year.

But it’s not just our homes that have an impact, offices also play a big role in have wasted energy.

Though businesses are becoming wiser to the financial and ecological impacts of leaving on lights, it’s still common to see empty office buildings lit up after hours.

The Energy Saving Trust found that leaving office lights on overnight will typically use enough energy over a year to heat a home for five months, while just one night of unnecessary office lighting wastes enough energy to heat water for 1,000 cups of tea.

Surely that’s incentive enough for any office manager to ensure that everything’s off when the last person leaves for the night.

As well as energy consumption, light bulbs also emit, well, light, and our skies at night have become increasingly brighter thanks to the effects of light pollution. People now travel great distances to find a truly dark sky, and in the UK we have several designated dark sky reserves, which aim to keep the sky in that area as natural as possible.

Dark skies attract stargazers and astronomers from far afield, but light pollution isn’t simply about stargazing. Artificial light at night is also compromising the health of humans and the planet’s ecosystems as a whole.

Over-light skies disrupt our natural body clock, or circadian rhythms, which are essential for cell regulation and hormone production, among other things. Health risks associated with disrupted rhythms include mental health and heart problems as well as cancer.

The wider effects of light pollution are quite startling.

Christopher Kyba, a research scientist with a special interest in light pollution, describes the effects of artificial light on animals and the ecosystem: “the introduction of artificial light probably represents the most drastic change human beings have made to their environment.

“Predators use light to hunt, and prey species use darkness as cover,” he explains “Near cities, cloudy skies are now hundreds, or even thousands of times brighter than they were 200 years ago. We are only beginning to learn what a drastic effect this has had on nocturnal ecology.”

If you click here, you will find a map, this map shows the spread of light pollution in our skies. It might seem like an insurmountable problem, but like all conservation, it begins with changing simple behaviours—and even a basic Google search will show you that ‘reducing light pollution’ always starts at home—with your very own light switch. By turning off lights that aren’t needed, especially outdoor or porch lights, you can help contribute to darker night sky.

Finally, if you’re yet to be convinced by arguments of disrupted ecosystems and excessive carbon dioxide, perhaps the chance to save some hard-earned money will help you flick that switch.

The UK wastes £170 million a year by leaving lights on unnecessarily, and the average household can also save around £13 a year by using lights only when they’re needed.

In 2013 we began transitioning from halogen bulbs to the more efficient CFL (compact fluorescent light) bulbs, with the former being banned from the EU by 2018. However, when it comes to saving money, there are better options, still: LED bulbs are even more energy efficient and an average household swapping entirely to LED lights are looking at savings of around £35 per year.