Metal Halide/HID (High Intensity Discharge) lighting has been the traditional lighting solution and standard to light up large interior areas such as retail spaces, warehouses, gyms, and factories. It has also been used for decades in most commercial exterior applications. The initial benefit of HID was the very high lumen per watt output, but that comes at a cost. HID lamps last only about 2-3 years and have a very rapid lumen depreciation over that time period. While they may start out at 100-110 lumens/watt initially, within a very short time period they get down to 50-60 lumens/watt and continue gradually until burnout. This means to keep light levels up you must change out the lamps constantly. Other shortcomings of HID include:
- Slow restrike time - 15-20 minutes once lights are turned off
- Low color rendering index rating (60-65) - the lamps appear to be pink, yellow, blue, white and do not match each other
- Very high wattage due to overengineering - they use 10-20% above their stated wattage with the ballast. Example: a 400W HID really uses 458 watts.
- Heat - HID lamps run so hot that the A/C system needs to work extra hard to keep the building cool.
- Maintenance - must replace lamps and ballasts constantly. Costs commonly include lift rentals, labor, and a lot of time.
In most applications with today's induction technology and costs to do an induction lighting retrofit, it makes sense to replace metal halides. A good starting point is to divide the HID wattage by 2, or take about half the current wattage the HID is using, and that is what you need for an induction lamp to maintain equal light levels. In most cases once analysis is done, you can be more aggresive and save between 60-70% energy to get the same light levels.
Here are a few retrofit examples that we commonly use with a lot of projects:
1. A warehouse has many 400W metal halide/HID high bay fixtures and the owner wants to have a 5-15% increase in current light levels. We would recommend a 200 watt induction lamp retrofit kit or a new 200W induction fixture if they want to replace their existing ones.
2. A facility manager currently has multiple 250W HID parking lot pole lights and wants to save energy and also cut down on maintenance costs, because the current metal halide lamps and ballasts are always going out or failing. They are more concerned about energy savings and the current light levels are adequate, even after 1-2 years of light depreciation from the HID bulbs. We would recommend maximum energy savings by going with a new 100W induction retrofit light kit or a new100 watt induction fixture. This also provides the same light levels as an HID bulb about 6 months to a year into its life.
3. A gym sports center currently has 1000W HID fixtures hung at about 35 ft over its basketball and hockey arena and is looking to save energy while keeping the play areas nicely lit. In this case there is not a 500W single induction lamp available, so the retrofit would have to include doubling up on two 250W induction lamps, or going with a new 500W induction high bay fixture. New high bay fixtures usually make more sense in this situation because even though they cost a bit more, the new fixtures include a 10 year warranty compared to a 5 year for the retrofit, and the new reflector and ballast system is designed specifically for the new induction system, where as retrofitting might be less efficient in terms of design.
Here is an example of a customer who wanted to save energy in a parking lot by replacing 400W HID's with a 150W bulb type induction retrofit kit. The energy savings is 67% in total because the 400W HID really uses 458 watts -
The one area where we caution customers on switching to induction from HID is when there is a need for indirect lighting (light bounces off surfaces or the ceiling and back down to the floor), and very far reaching areas, typically in stadium and field lighting. Examples include indoor tennis centers where players are concerned about light in their eyes and glare, stadiums, and outdoor playing fields. Metal halides put out a tremendous "punch", that can reach 100-200 ft if coupled with enough lights together. Induction lighting does not have the same reach, and in these cases it often makes sense to switch to a pulse start HID system or the newer electronic ballasted HID systems.