Energy or maintenance: where can you save most?

Before we get into the numbers let’s consider what makes an LED luminaire different from other lighting. It's solid state semiconductor technology with no air, glass or fragile filaments - the most robust and efficient light source - and contains no mercury or harmful materials.

The early LEDs used in luminaires were expected to last 20,000 hours, but the current crop can exceed 100,000 hours of lifetime. As they don't shatter or fail like traditional lighting but just gradually fade over time, a top quality luminaire may have a rated lumen maintenance life of L70 at 100,000 hours, meaning it will operate for that length of time before falling below 70% of its initial light output level.

And all reputable LED fitting manufacturers will provide a five or even ten year warranty for their products, so it should easily be possible to achieve payback at least once within the warranty period.

In one case a distribution warehouse achieved a 1.1 year payback from savings on energy alone by lighting with a 150W LED high bays in foreground and 400W HPS at back.

Previously the facility had a mix of 136x250W and 100x400W high pressure sodium (HPS) high bays actually drawing 280W and 430W each. The lights were in use 24/7, partly because they took so long to re-strike after switching off.

By replacing them with only 126x150W LED high bays the Watts/sqm came down from 3.85 to 1.05 and annual CO₂ reduction was 271 tonnes. Annual energy savings amounted to £42,000, but additional savings could also be accounted from avoidance of carbon tax, reduced lamp maintenance and replacement and by claiming Enhanced Capital Allowance.

If dimming and proximity sensors were also introduced, even greater savings could be achieved, but the project manager admits to keeping that initiative for next year when his board will ask him to deliver even greater energy savings.

In the dark: Before the LED high bay installation

In another example, a bulk storage facility lit by 8 LED high bays achieved 1.3 years payback from savings including maintenance. Previously, it had 13x400W HPS which were drawing 440W each. The lights were only in use 8 hours a day, 5 days a week, 50 weeks a year, so by replacing them with 8x172 LED high bays the energy savings amounted to only £695 against an investment of £4,320.

The picture changes, however, when maintenance is taken into account. The heat generated by the HPS was burning cargo dust onto the polycarbonate lenses and greatly impairing their performance. The annual maintenance of lighting in the bulk store involved the cost of two men for one week plus the hire of a cherry picker, the cost of 13 replacement polycarbonate lenses and 4-5 lamp changes amounting to £2,297 annually.

All of this can now be eliminated by using LED high bays which can be expected to last for 10 years or more on such low usage, so they continue to pay for themselves in combined energy and maintenance savings throughout their lifetime.

So it’s clear that in some cases the financial savings made possible by improving energy efficiency are only a part of the bigger picture. Maintenance efficiency can often eclipse energy efficiency to increase the financial savings while also reducing disruption to the business, so it’s worth exploring this aspect fully when trying to calculate your likely payback period.

Summing up the benefits of LED technology:

• It consumes less power.
• It has instant-on ability.
• It performs better in extreme temperature conditions.
• It lasts longer to reduce maintenance costs.
• It contains no mercury or hazardous material.
• It generates a better quality of light.
• It provides better ROI compared to conventional technologies.
• It’s ready for integration into ‘smart’ lighting solutions like dimming and remote monitoring.