Determining how many high bay lights you need comes down to two important factors, are they for a retrofit installation or for a new installation.
When it comes to a retrofit installation, you need to take note of what type and how many fixtures you currently have installed. Since LED lights require less energy to deliver the same kind of light output as HID, or metal halide, chances are you do not want to base your decision on wattage. For example, a 400-watt high bay with LED technology produces the same light output as a traditional 1000-watt high bay with HID technology. So if you have 10 - 1000-watt HID high bays in your space, you would want to replace them with 10 - 400-watt LED high bays to ensure you have the same amount of light as before.
Now, if you are working on a new installation project its a little bit different. For instance, if you're going with high bay lights with LED technology then you would look at the lumen output they produce. Here are some examples:
• 20-29 feet you will need a high bay light that produces 20,000 to 29,000 lumens
• 30-39 feet you will need a high bay light that produces 30,000 to 39,000 lumens
• 40-49 feet you will need a high bay light that produces 40,000 to 49,000 lumens
The correct spacing of high bay lights is an important factor in determining how the light output will be dispersed throughout an area. Below are some examples of some spacing options to get the best light output for your space:
• At a mounting height of 20-feet, if the high bay lights are spaced every 15-feet, the light output would be bright. If you space them every 18-feet apart, the light output would be normal or adequate.
• At a mounting height of 30-feet, you can bump the spacing up to 20-feet apart and still have a bright light output. However, if your just looking for a normal light output, then 25-feet spacing would be sufficient.