Lighting represents a significant portion of energy consumption in commercial buildings, surpassed only by HVAC in most cases. Many upgrade projects focus on indoor lighting, but significant savings are also possible by upgrading outdoor fixtures. In many buildings, outdoor lighting fixtures operate for more than 12 hours per day.
This articles provides recommendations for outdoor lighting upgrades, with the goal of minimizing electricity consumption while providing optimal performance. LED lighting is almost always a good investment, thanks to its low power consumption and long service life.
Most outdoor fixtures use HID bulbs (high-intensity discharge), which have a potent light output but a low efficiency. These bulbs also suffer from a short service life, which means they require frequent replacements. As an example, consider a commercial building that uses 50 outdoor fixtures with HID bulbs, having the following features:
450 watts per luminaire, which results in a total consumption of 22.5 kW
Metal halide (MH) bulbs with a rated service life of 10,000 hours
An operating schedule of 12 hours per day (4,380 hours per year)
Since a load of 22.5 kW operates 4,380 hours per year, the estimated annual consumption is 98,550 kWh. For a building owner paying 15 cents/kWh, this results in an outdoor lighting cost of $14,782.50.
Based on the rated service life of 10,000 hours, you can expect the MH bulbs to last slightly over two years. However, MH bulbs are characterized by a quick degradation of their lighting output, typically losing 30% in just 5,000 hours of use. Considering this factor, you may find that a lighting replacement is necessary in less than two years.
The MH400 bulbs used by these luminaires normally cost over $10 each, which means you must spend over $500 for a complete replacement. If you hire an electrical contractor for the lamp replacement, you must also consider labor costs.
A typical LED upgrade for this outdoor lighting system would offer the following characteristics:
150 W per luminaire, 7.5 kW in total
Rated service life of 50,000 hours
This means that electricity consumption is reduced by 67 percent, while the service life becomes five times longer. The lighting expenses would be reduced to $4,927.50/year, and the LED fixtures can operate for more than 10 years without a replacement.
Assuming an upgrade cost of $600 per fixture, the entire project has a budget of around $30,000. Since the LED upgrade saves around $10,000 annually, the payback period is around 3 years. Most commercial lighting products now come with a warranty of 5 years or more, which ensures a return on investment.
Not all lighting fixtures have the same beam shape: while some products spread their output over a wide area, others produce a narrow beam that is concentrated downward. When purchasing outdoor lighting fixtures, make sure they cover your property without causing glare for neighbors, drivers or persons walking by.
A very important design decision is the lighting distribution produced by the fixture. In the case of LED lighting, there are six main types:
|
LED Distribution Type |
Description |
|
Type I |
Concentrates the lighting output towards the sides, with minimal output towards the front and back of the map. |
|
Type II |
Concentrates light at 25° angles towards the front. |
|
Type III |
Concentrates light at 40° angles towards the front. |
|
Type IV |
Concentrates light at 60° angles towards the front. |
|
Type V |
Emits light in all directions, in a circular pattern. |
|
Type VS |
Also emits light in all directions, but in a square pattern. |
For instance, a Type V distribution is suitable in the middle of your parking area, but not on the edge of your property, since it may project unwanted lighting outside. A Type IV fixture would be more suitable at the property limit, since it minimizes the amount of light sent backward.
Glare is the visual impairment caused by a concentrated light source, and the glare performance of outdoor lighting can be described with the BUG rating. People often assume that the BUG rating is related with insects, but actually it uses the first letters of backlight (B), uplight (U) and glare (G).
Each letter has a scale from 0 to 5 based on lamp performance.
The best possible score is B0 U0 G0, while the lowest performance score is B5 U5 G5.
The best recommendation to achieve optimal lighting is getting a professional design. This ensures that you will be using the most suitable fixtures for the outdoor areas of your building.
There is a large number of LED vendors in the market, and a lighting upgrade can yield poor results if the fixtures installed are of low quality. The best recommendation is looking for lighting products labeled by ENERGY STAR or the DesignLights Consortium (DLC).
Note than ENERGY STAR focuses on residential lighting, while DLC focuses on commercial lighting. When a specific lighting product is eligible for both labels, ENERGY STAR takes priority because the program is run by the US Environmental Protection Agency.
Both programs have stringent requirements, and their labels indicate that lighting products have been subject to demanding laboratory tests. If there is a lighting rebate program from your local government or electric company, it is very likely that only labeled products are eligible.
When outdoor lighting is controlled manually, the fixtures may be left on during daytime, which represents a waste of energy. A lighting control ensures they will only be used when necessary.
Some lighting control systems have daylight sensors, and outdoor fixtures are automatically switched off in the morning. An advantage of these lighting controls is that they activate outdoor lighting when a cloudy day is particularly dark. There are also time-based controls that use a simple lighting schedule, but they require manual activation if you need outdoor lighting on an overcast day.
An outdoor lighting upgrade is an excellent energy efficiency measure, but only if you select adequate fixtures for your property. A professional inspection of your outdoor lighting is strongly recommended before proceeding with an upgrade.
LED lighting offers an excellent return on investment and a long service life, reducing the need for frequent lamp replacements. Purchasing high-quality LED products with an optimal beam shape is very important, and you can optimize their operation with a lighting control system.