How to select the correct LED corn bulb

Many times we find that people who needs to replace a metal halide bulb, a high preasure sodium or an halogen chose the wrong kind of LED corn bulb. Here is a guide on how to use the right one.

The first thing we should look at is the fixture where the bulb will be used. The most comon one is the high bay aluminum reflector or acrylic reflector. For this type the cillindrical corn bulb is one option, but the other option is the conical shape with the base at the wide side of the LED corn bulb. This shape will direct the light more downwards with a 140° x 360°, thus being more efficient if the light is needed below the bulb, specially when using nthe acrylic reflector or no reflector at all.

If you need to replace a bulb in a top of post, like inside a globe or an acorn, you can again use the cillindrical type to go as far as possible or you can use a conical shaped LED corn bulb where the base is on the thiner part of the cone. These LED corn cobs shine light all around but downwards, Most applications are on posts in comunities where most likely the bedrooms are on the second floor and you want the street and sidewalk well illuminated without bothering people sleeping. 

For those fixtures with reflectors definitively you need to use a one side or 180° LED cob light. If a 360° or cillindrical corn bulb would be used, the light bouncing back from the reflector will be lost as light and instead converted into heat, this will raise the LED corn bulb temperature and will "cook" the LEDs reducing their expected life thus reducing the duration of the product. About 40% of the light will be lost. If the cillindrical LED corn cob is let's say 50 Watts with 6500 lumens, still will burn 50 Watts but only about 3900 lumens will shine.

With current efficacy about 140-160 lumends per Watt and using the correct LED corn bulb you can estimate to replace a metal halide or HPS with 1/5 the power in LED, saving more than 80% in electric bill. For Halogen estimate 1/8th the power and incandescent 1/10th.