Whilst we don’t envisage having to answer this question in 3 or 4 years’ time, it still often comes up at the moment – What is the Return on Investment for installing LED lighting? However, to answer this we have to go a lot more deeply into the application of the lighting, rather than just what we are replacing.
Broadly speaking, in comparing LED to LED there are typically two ways of driving LED’s – for effectiveness (maximum light output) or for efficiency (maximum lumens/watt). When running LED’s for effectiveness, you are driving them hard to get as much light as possible from as small an area as possible. This typically reduces the size and weight of the heat sink and the number of LED’s. In this scenario a 5W LED may be operated at 5W. Whilst this gives the maximum light output per cm2, the LED’s are not running very efficiently from an electricity-usage perspective. This is due to the fact that LED’s lose efficiency as they get nearer their maximum output. Therefore a 5W LED running at 1W may well be twice as efficient in terms of lumens/watt, compared to the same LED running at 5W. This means that to have a lamp designed for efficiency means more LED’s, bigger surface area, more weight and, obviously, more cost.
The other comparison factor would from metal halide to LED. A well designed metal halide fitting like the Phillips MVP is a very efficient module in terms of lumens per watt. When new, a traditional 2kW metal halide needs a minimum of 1600-1700W of LED to come close. For a LED fitting this size it means that the LED could well be double the price of the MH units. Multiply this by 24, 48 or whatever is required for your lux levels, and this could be a significant amount of money.
So, when we come to the question of ROI we have to look at the application. In a warehouse with dozens of high bays which are running 24 hours/day, the criteria are very different to a sports pitch which is only used a few hours a week. In the warehouse there is no airflow, the lights are on for long periods of time and are often inaccessible. Running 100 x 150W lamps for 24 hours a day, 365 days of the year equates to 360kW/day, or 131mW (million watts) per year. By comparison, a football club using the field for training a few times a week would use around 10mW/year. The club therefore should be more concerned about the cost of the fittings and the poles. If a club were to spend an extra $20000 on a more ‘energy efficient’ system due to increase in luminaire weight and the consequent pole strength, it would take a long to time to get the value back.
This brings us back to the ROI question for sports fields. As seen in the above examples sports lights are designed around output rather than efficiency due to the short time they operate in a year. ROI therefore has to be calculated on the cost over the whole life of the project. In this way efficiency or ‘use of electricity’ becomes much less important and maintenance and hassle factor takes over. Whilst metal halide fittings perform extremely well and are cost-effective to buy and run, they don’t operate at peak performance for very long – typically around 400 hours. This means that after 400 hours the output is nearing about 75% of what it was at new. The bulbs then turn from orange to pink and finally stop working. Although the actual cost of the bulbs is not that high, bulbs for some older fittings are more and more hard to find and certain models are no longer made. Having said that, for those that can get bulbs, the bulb is the cheap part – fitting them becomes expensive. The costs would include the electrician and some form of high lift apparatus. For many rural towns a boom lift to 30m may be many kilometres away, adding to the cost significantly. This can result in bulb replacements costing over $5000/year, even if they are batched together. Over a 10 year period this significantly increases the cost of what looked like a really inexpensive option. By contrast, LED fitting typically come with a minimum of 5 year warranty. If the contract is locked down well, most (reputable) companies offer the warranty to cover parts and labour, including high-lift equipment. This means that there is an average saving of $25000 for the first 5 years, even for a relatively small club.
Conclusion
Don’t take the face value of the raw dollars comparison of metal halide versus LED. Do the calculations carefully and make sure there is still an advantage after 10 years. The other risk factor is many metal halide suppliers have stopped manufacture of their fittings so spare parts like ballasts and bulbs may not even be available in 10 years. This may result in you having to buy spares and keep them in stock which further adds to the costs. Add the extra hassle of delayed start-up of metal halid.
