lightbulbThe cliché most commonly used to describe a guiding principle behind UK energy policy is "keeping the lights on". I say: let's turn them off instead. Based on what other countries have done, we could save £1.192 billion every year. And that's just the start of the benefits.

The French have just passed a law on the lighting of non-residential buildings.

Beginning on July 1, it requires shops and offices in France to turn off their lights one hour after the last worker leaves a building. All shop window displays will be turned off at 1 a.m. Shop windows may only be lit from 7 a.m. or an hour before opening time.

Necessary public lighting will not be lit before sunset. Exceptions will be made during Christmas and other significant events, as well as in some tourist and cultural areas.

This is expected to save about two terawatt-hours of electricity every year, about the same as the annual consumption of 750,000 households. Based on the average UK electricity bill that would equal £842.25 million.

It will also prevent the release of about 250,000 tons of carbon dioxide into the atmosphere. The French Environment Minister, Delphine Batho, hopes that the decree will change the public’s attitude towards energy-saving practices and make France a pioneer in preventing light pollution.

It will save money for companies and for local authorities. Should the UK follow suit? Could it go even further?

Turning the lights off in streets and non-residential buildings would have many benefits. Most species of bird use the position of the stars to migrate and to navigate at night, but artificial light can lead them off-track and away from their migration routes.

In Slovenia, they have spotted a direct connection between the lighting of public buildings, which began following independence, and the disappearance of insect life. There used to be 460 species of moths in a church on a hill in Kranj (in north-western Slovenia). Since it began to be floodlit at night, this has dwindled to no more than twenty.

Light pollution is opposed by the Campaign for the Protection of Rural England, since it ruins our appreciation of the night sky. The Clean Neighbourhoods and Environment Act 2005 made light nuisance subject to the same criminal law as noise and smells. It applies to "artificial light emitted from premises so as to be prejudicial to health or a nuisance".

It does not necessarily cover the nine million or so streetlamps found in the country.

And this is as far as the law goes in the UK: legislation says nothing about energy efficiency or nature conservation.

There is a clear case for public lighting to be curtailed dramatically, providing that safety is not compromised, for three reasons:

• Economics;
• Curbing carbon emissions; and
• Nature conservation.

Slovenia has the toughest light pollution laws in the world, the Slovene Light Pollution Law. It was passed in 2007, following 12 years of campaigning, and has resulted, five years later, in its capital Ljubljana replacing half of its street lighting with new, less powerful versions, saving an estimated 40 to 60% of energy.

Its fundamental principle is: ‘No lighting is allowed to shine above the horizon’. With a population of two million, it is expected that over the first ten years, up to €10 million worth of energy will have been saved.

But with new technology it is possible to go much further than either the French or the Slovenians. Smart, wireless technology can mean that street lighting, right down to individual lamps, could be controlled independently to take care of particular circumstances.

For example, they could be adjusted to respond to weather, individual need and the timing of events such as a concert or sports match.

According to Jacob van der Pol, of NXP Semiconductors in the Netherlands, a company which makes intelligent lighting: "If there is a football match, the lights in the area can be told to come on when everyone is leaving and dimmed after they have gone. The technology allows you to adapt to circumstance."

The German city of Dörentrup has been pioneering this type of solution. By default, every night at 11pm all street lights are turned off.

Inhabitants can then request a light to be turned back on as needed, by sending a code to a special phone number, called Dial4light. Each street has its own code, that can be found either on this website, or on each lamp-post.

It has been proved to be so successful that it has been extended to 11 other cities, but it has not been without controversy and consequent refinement.

Residents originally had to register on the website before being able to use the system, but this requirement met with protests and has been withdrawn. The arrangement even covers the lighting of sports facilities and parks. The request to switch on the light results in the light staying on for 15 minutes after which it goes off automatically, but that may be renewed, and the policy is subject to evaluation.

Following complaints from residents on inhabited streets about safety, the latest tests are confined to streets which are not inhabited. The city of Hennef reckons that, if applied to the entire city, Dial4Light could save about €300,000 in electricity costs per year for street lighting.

Hennef has a population of just 46,342. Based on this, if the policy was applied in a similar way to the whole of the UK (population 62,641,000), it would save the UK £349.52 million per year.

If the UK also adopted the French law, it would save a further £842.25 million, resulting in a total of £1.192 billion each year.

This is not to mention the other benefits on wildlife, light pollution and curbing carbon emissions.

Since cost pressures are forcing many municipalities to save on the lighting of public streets and roads, this would be an excellent and simple strategy to copy in the UK.

And for building managers, installing low-energy, high-performance LED lighting, with controls allowing them to switch off at night or whenever the building is unoccupied, would save a lot of money, reduce their carbon footprint and, done properly, have no negative impact on business operation.

It's an illuminating thought.