Choosing the right lamps for a lighting upgrade is very much a matter of horses for courses and there is no one size fits all solution. LEDs are a case in point, says Simon Dixon of Riegens Lighting.
In the current economic and environmentally aware climate many building operators, and the specialists they employ, are faced with something of a balancing act. On the one hand they need to reduce energy consumption and carbon emissions. On the other hand, capital budgets are tight and a sensible return on investment (ROI) is vital.
Consequently, lighting upgrades are proving particularly popular because they often represent a quick win with a relatively short ROI. However, it’s still important to ensure that the best solution is selected and this doesn’t always seem to happen.
Cost of ownership
A case in point is LED lighting, which undoubtedly has a growing number of uses but in my view is still not a universal panacea for every lighting application.
Yet the publicity that LEDs have received is leading some end users to believe that they must install LED lighting to be sustainable.
It seems to me, therefore, that consulting engineers have an important role, and something of a challenge, in educating end users. And to do that they will have to be able to explain the factors that contribute to the total cost of ownership mantra that currently prevails.
Clearly there are several aspects to cost of ownership, and these need to be sufficient to compensate for the much higher price of LED fittings. After all, LED sources typically cost at least ten times as much as the lamp they are replacing!
Energy consumption is the ‘headline act’ but the ROI is also influenced by maintenance/re-lamping costs and lamp disposal. Many ROI calculations involving LEDs depend heavily on these latter two criteria because of the long life of LED light sources.
This means that there are certain lighting applications where LEDs are an obvious choice. For instance, replacing 50W halogen lamps with 7W LED sources gives such a huge energy saving that this is the main contributor to the ROI and maintenance is less of an issue.
When looking at replacing fluorescent or indeed HID lighting with LEDs, the calculations aren’t so clear-cut because the difference in installed electrical load isn’t as marked. For example, there are 600mm x 600mm LED fittings on the market that generally consume more power than a 600mm x 600mm fluorescent fitting, and produce less usable light.
In these cases the ROI is all down to the maintenance aspects and the lighting needs to be in use for considerably longer than the payback period to make it worthwhile. In other situations, though, the maintenance savings are a major benefit. An obvious example is street or amenity lighting where re-lamping is a particularly costly procedure because of access difficulties. The fact that LEDs perform particularly well at low ambient temperatures is also a bonus.
Make it pay
I am suggesting, therefore, that every project should be assessed on its merits rather than simply following a trend that has a feel good message. In our experience, most end users are receptive to a well-reasoned argument that shows them how they are getting the most cost-effective solution that also helps them reduce their carbon emissions.
To give an example of this, there are still many office lighting installations that are still using T8 fluorescent lamps. In most cases the lowest cost of ownership, taking everything into account, will result from upgrading these to T5 lamps. Simply replacing 3 x 14W T8 fittings with 2 x 14W T5 luminaires will reduce the electrical load by as much as 47% with a relatively low capital cost – and extended re-lamping cycles into the bargain. So this solution will deliver a fast ROI within the life of the installation.
As an aside, it’s also worth pointing out that retrofit LED tubes, for replacing fluorescent tubes, tend to have major thermal management problems and are six times as heavy as fluorescent tubes – putting a strain on the lampholders.
In a different situation, 400W SON lamps in a high or low bay fitting can be replaced with anything from a 3 x 28W to a 4 x 80W T5 fittings (depending on mounting height) to reduce energy consumption while maintaining illuminance levels. In this case of course, because of the mounting height, LEDs would probably give a faster ROI because of the reduced maintenance costs. However, they would not be able to maintain the required illuminance levels.
So I would urge anyone who is involved in the specification of lighting to give due consideration to the latest light sources, and make full use of them when they offer real benefits. But I would also urge them not to adopt a single type of light source as their default position.