How to Retrofit a 400 Watt HID Fixture

Where do you start? What are the options? Should you consider a Retrofit kit or use a 360 degree post top screw in bulb? Here are some of the things you should consider before you purchase...

You’ve heard that switching to energy efficient lighting can save money, but where do you start?

Old 400W HID (Metal Halide and High Pressure Sodium) systems are installed almost everywhere in commercial and industrial applications. You see them in parking fixtures, flood lights, wall packs, cobra heads and for lighting indoor spaces like factories, warehouses and gymnasiums. Energy costs are rising, so how can you take advantage of converting to LED?

Well there are options available for you. What works for you is totally dependent on your fixtures and your goals. You can expect at least 50% energy savings. You should expect more. Add controls, and you can achieve up to 90%. 

Things to Consider before the HID to LED Conversion

Who will do the installation?

Some options require the use of a licensed electrician. Other options allow you to screw in a bulb into the existing socket. But this should not be the determining factor in your decision.

What retrofit options do I have?

Typically, you have 3 options to convert from HID over to LED

  1. New fixture – Maybe your fixtures are old and are failing. Replacing them would be your best option.
  2. Bolt in Retrofit Kits – Requires removal of bulb, ballast, reflector and socket. Kit contains everything you need to add LED Head and LED Driver.
  3. Screw in LED lamps. This would require you to remove the ballast and direct wire the socket to the power source. Post Top Bulbs are a good example of this type of retrofit.

How much does it cost?

Not as much as you think. Prices have come down a lot over the past few years. Rebates may be available to help offset the purchase price. Rebates can be obtained for both new fixtures and retrofit options. Once we understand your goals and needs, we can help you find the best option including looking for rebates.

What are the Differences between LED and HID?


HID is a relatively old technology, consisting of several bulb types that include low pressure sodium, high pressure sodium, mercury vapor and metal-halide.

When you convert from HID to LED, you have to take into account 'ballast draw' of the HID bulb. What this is is the amount of energy the ballast consumes to power the bulb. It can add as much as 15% to the entire draw of the bulb. So a 400W HID bulb actually consumes about 460W of energy. A great deal of the energy consumed produces heat.

HID  bulbs are omni-directional. They distribute light in every direction. It requires a reflector to "gather" all the light and redirect it to the ground.

400W HID bulbs are commonly found in fixtures not mounted higher than 30 ft above the ground. Anything higher than that, we typically find 1000W HID (or the equivalent in LED)


Never buy a LED bulb based on watts to replace HID. Determine the amount of lumens you need, and get the most efficient LED bulb / fixture that produces that amount of lumens.

LED does not generate a lot of heat. It does generate some, the lights can get warm, but it is significantly less them HID lights. That is one of the reasons LED is more efficient, it uses the energy to produce light instead of heat.

LED Light is directional. The light goes where its needed. You need less LED Lumens to replace a 400W HID light that requires a reflector to gather the lumens and direct them where they need to go. Reflected light is less efficient than directional light.

5 Easy Steps to Convert from 400W HID to LED

Step 1: Do you have a 400W HID Fixture/Bulb?

These bulbs are rather big and there are 2 sizes. One is larger than the other. The smaller of the two is 8-9" long, the larger bulb is about 11-12 inches long. Somewhere on the bulb, you should see the bulbs identification markings, and it should say 400 (to identify 400 watts HID)

Step 2: Determine the voltage

Not that this is terribly important at this point, but you need to order your solution with the right voltage. LED comes in basically 2 driver options, 100-277V and 277-480V. They are auto-switching, so it will figure out what voltage you have and switch the first time it is used. But, make sure you have the right range selected or you will toast your driver.

Step 3: What is Your Goal?

A. Is it Energy Savings?

Reduction in energy spend up to 75% is a compelling reason to convert from 400W Metal Halide to LED. That should significantly reduce your utility bill each month.

B. Reduction in Maintenance Costs?

LED's life span is much longer than HID. Large commercial facilities can spend a lot of time and money. If you are not changing bulbs, you are saving money.

Increase / Decrease in light levels (brightness)

Maybe your area is under lit? Over lit? Photometric reports done before you lets you adjust the light so there is no guess work. You simply use the software to help you decide what the best outcome for your area is.

Step 4: What Type of HID Fixture do you Have?

For the most part, our Retrofits are designed to replace a 400W Metal Halide or HPS bulb and will fit into the fixture cavity without issue. If you use one of our directional light replacement kits, you can make even more space by removing the reflector. Besides creating more installation space, it has 2 other side benefits.

  1. Creates more air space to keep the fixture cool
  2. To preserve the warranty, the reflector is not needed and the extra air space helps keep things cool.

For the most part, the standard Retrofit kit should be chosen over a post top bulb except in acorn style post top fixtures where a 360 degree pattern is required.

Step 5: Make Your Selection

Unlike some online companies, we offer both new and retrofit solutions, so we are not biased in one solution over another. Many times we have heard some customers call us and tell us 'Company A' claims the only solution is a new fixture. And when you go to their site, that's all they have. Naturally, they are going to recommend what they have over what they don't. In our case, there are many factors that you need to consider to come up with the best solution for you.

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