What if all the UK's streetlights were upgraded with LEDs?

What if the UK’s 5.5 million streetlights were converted to LED? I reckon local authorities, government bodies and the Highways Agency would save about 770,000,000kWh a year and prevent the emission of 430,000 tonnes of carbon dioxide.

That calculation is based on conservative assumptions – after all, there is a huge range of LED wattages and associated lumen outputs. There are essentially two reasons for this: LEDs could be fitted as retrofit LED lamps or integrated LED lanterns, and many different types of streetlights are used throughout the UK.

To simplify the calculation I have assumed an rating of 100W for a typical UK streetlight. Taking into account summer and winter hours, I have assumed 4,000 annual operating hours.

To calculate efficiency I have compared a number of LED replacement options. For example, the Light Efficient Design 35W LED luminaire will replace a 55W SOX and represents a 36 per cent saving. Some manufacturers claim higher savings, but I have assumed a saving of 35 per cent. This does not allow for gear losses, but even without this percentage the scale of the estimated energy saving is significant.

One 100W streetlight operating for 4,000 hours a year, replaced with LED sources, saves 140kWh a year, assuming a saving of 35 per cent.


Now imagine 5.5 million streetlights each saving 140kWh a year. For local authorities, government bodies and the Highways Agency this is the tip of the iceberg.

The financial savings generated from reduced maintenance are the key to achieving ROI, although many organisations find it difficult to assess maintenance costs accurately.

There is a trend towards turning streetlighting off from midnight, a practice that affects both motorist and pedestrian safety. The introduction of LED technology not only improves energy efficiency but also enables dimming. I am not suggesting that streetlights are dimmed to 10 per cent, the contrasts may be too great, but dimming to 30 per cent will save energy while leaving the area illuminated. There are a number of Wi-Fi systems that will enable lighting control from a central base. Perhaps something streetlighting managers should consider.

A word of warning. I have, on my travels around the country, seen a large number of LED lanterns that are either not operating at all or left on 24/7. If an LED is operating 24/7 you are throwing away most of the energy efficiency benefits. Also, there are lanterns that have turned through 90 degrees because of the lantern design. The introduction of LED streetlighting does not mean zero maintenance, some organisations have clearly not read the small print.

Perhaps this is another message for the government.

Comments 6

Useful article. Could you point to the study results (which presumably exist), pertaining to your assertion that turning off lights at 12:00 impacts motorist & pedestrian safety?

It would be great if they lit the road evenly (and not everyone's front gardens too), with little glare, lasted a long time (some of the 1960s SOX lanterns are still going strong, so that's a good target for longevity), and had replaceable LED modules and drivers which won't go obsolete in a couple of years.... it could be done, but I've got a feeling I'm going to be disappointed...

It would be great if they lit the road evenly (and not everyone's front gardens too), with little glare, lasted a long time (some of the 1960s SOX lanterns are still going strong, so that's a good target for longevity), and had replaceable LED modules and drivers which won't go obsolete in a couple of years.... it could be done, but I've got a feeling I'm going to be disappointed...

Councils need to plan far enough ahead to do this on a rolling replacement to avoid unmanageable up front capital cost. Essex County Council are currently top dressing all their roads because they can't afford to resurface them properly (resulting in a noisy surface for drivers and an unpleasant one for cyclists) so I can't see them doing a proper job of lamp replacement. Does anyone have payback periods for this? I've seen average figures of around 6 years mentioned?

Southend Borough Council are doing this. They are using grants to replace every single lamp with an LED unit, centrally controlled. This will save them huge amounts of money. In contrast, Essex County Council have been turning off their lights at night increasing the perception of reduced safety. It will be interesting to see the results in 2017.

The only way this is going to work is if the local authorities put sufficient resource in place to carry out proper design of these schemes, the public perception will not be favourable. I have just had a discussion with my local authority, which has received several hundred complaints, and was advised that 8 different versions of one particular luminaire is sufficient to adequately illuminate 90% of the road network. Unfortunately, in many cases, there is a hot spot directly below the luminaire and virtual darkness in between. Unfortunately, we will have to wait until October or November to undertake a meaningful night time survey

Leave your comment