HID or LED Lighting, Which Is Better?
HID lighting – high intensity discharge lighting – replaces the filament of a light bulb with a capsule of gas. The light is produced by an arc discharge between two closely spaced electrodes. This discharge is sealed inside a small glass tubular capsule and requires a ballast to carefully regulate the voltage supplied to the capsule of gas.
LED – light emitting diodes – are light sources utilizing diodes that emit light when connected to a circuit. LED is housed in a plastic bulb, release a large number of photons outward in a concentrated light source.
It’s easy to find a report or an article that lists the substantial benefits of replacing HID lighting with their higher energy savings counterparts, LED. But what makes that so?
Comparing the efficiency can be a little tricky. HID lighting is typically evaluated based on source efficiency, which is measured with a bare lamp at room temperature. But this approach doesn’t account for the impact on lamp performance in the location in which it is installed. You may recognize the measurement lumens per watt, which reflects the amount of light produced by the source, divided by the power required to operate it. In some cases, some forms of HID lighting such as high pressure sodium and metal halide can appear very efficient. However, it doesn’t accurately reflect how much light is delivered from the light source to the target area. And that can be a huge discrepancy in the case of a street light or a parking lot.
System efficiency is measured based on how many lumens actually reach the target area, not simply how many lumens are emitted from the source. System efficiency is always lower than source efficiency due to:
Trapped light – the ineffective light that cannot be redirected to its targeted location
Protective covers and lenses – luminaires almost always have protective covering to safeguard it from the environment
Operating temperature – especially with outdoor lighting, temperatures can vary to all extremes. Source efficiency is measured at a standard 77-degree Fahrenheit. Any other environment will perform differently.
Power supplies – different light sources require different ballasts or drivers to convert into light
HID lighting may have a source efficiency around 120 lumens or higher. But when operating under the four conditions above, they can quickly reduce to 30 lumens or less.
LED lighting has a source efficiency of 100 lumens or higher, but there are no losses from trapped light due to the focused output of LED. LED also requires less protective covers and lenses for production, and the power drivers are generally more efficient than HID ballasts. Temperature efficiencies remain about the same.
Thinking about making the change from HID lighting to LED lighting for your commercial property or parking lot? Give us a call today.