How to Convert a T12 Fluorescent Fixture to a T8

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In an effort to promote energy efficiency and protect the environment, the U.S. Department of Energy banned the production of magnetic ballasts for T12 fluorescent lamps in 2010 and the production of T12 fluorescent lamps in 2012. One alternative is to replace or retrofit existing fixtures with more efficient and more environmentally friendly electronic ballasts and T8 fluorescent lamps.

Differences Between T8 and T12 Lamps

  • A 48-inch T8 lamp produces 2,600 design lumens using 32 watts, while the same size T12 lamp produces 2,520 design lumens using 40 watts. Although brightness is basically the same, less energy is used by the T8.
  • T8 lamps have a 1-inch diameter and T12 lamps are 1.5 inches in diameter. Because of their smaller size, T8 lamps trap less light within the fixture and create more usable light.
  • Because a T8 uses rare-earth phosphors, the light emitted has superior color characteristics and the lamp has a higher efficiency compared to the T12, which uses less-expensive halophosphates that typically provide only good color quality or high efficacy.
  • The T8 lamp uses an electronic ballast that produces 265 milliamperes as opposed to the 430 milliamperes magnetic ballast used on T12 lamps. The higher frequencies produced by an electronic ballast create 10 to 12 percent more light output than the magnetic ballast operating a T12 lamp at 60 hertz. The electronic ballast also produces less flicker and noise in addition to less heat, which helps to prolong lamp life, slow lumen depreciation and reduce additional energy use for air conditioning. One electronic ballast can operate up to four lamps. A magnetic ballast typically operates only up to two lamps.

T8 Retrofit Conversion Kits

Converting a T12 fixture into a T8 fixture can be easily done with a retrofit conversion kit. Kits are readily available and can be installed with a few basic electrical tools. Most kits come with all material needed to convert a 4-foot or 8-foot T12 light fixture and complete instructions, which vary by fixture size and lamp count. Some parts are pre-wired and will require only ballast leads to be connected. Because you have recycled your original fixture, the process is economically and ecologically friendly, and energy savings can be as much as 40 percent.

Although a complete replacement of your existing T12 fixture with a new T8 fixture is an alternative, it may not be the cheapest or easiest solution. Evaluate your particular situation and environment to determine what will work best for you.

How to Install a T8 Retrofit Conversion Kit

Things You'll Need

  • Wire cutter/stripper

  • Nut driver

  • Wire nuts

  • Screwdriver

Step 1

Turn off power to the fixture at the circuit breaker.

Step 2

Open the lens cover on the fixture, if applicable.

Step 3

Remove the ballast cover from inside the fixture. This is usually a raised metal cover that runs down the center of the fixture and is secured in place by screws or tabs.

Step 4

Cut the wires that lead from the old ballast. Using a nut driver or screwdriver, remove the nut or screw securing the ballast to the fixture. Dispose of used ballast properly.

Step 5

Remove the socket brackets and sockets from the fixture. These may be screwed to the fixture or secured by tabs. 

Step 6

Install the new T8 ballast in the fixture using the nut or screw and the applicable tool.

Step 7

Connect the wires from the ballast to the new sockets supplied with the retrofit kit; follow the schematic on the T8 ballast. Install the sockets into the new brackets, then install the brackets into the fixture per the instructions included with your conversion kit.

Step 8

Connect the line voltage wires that supply power to the fixture to the ballast with wire nuts and ground the fixture. Refer to the schematic on the ballast and the instructions provided by the manufacturer of your kit.

Step 9

Reinstall the ballast cover and install new T8 bulbs. Reinstall the lens cover, if applicable. Reset breaker.


Check your local laws for the proper disposal of your T12 magnetic ballasts and bulbs.


Using a T8 lamp with a T12 ballast will result in premature lamp failure due to overheating. Using a T12 lamp with a T8 ballast will result in premature ballast failure due to overheating.


Bill Goodwin

Bill Goodwin has more than three decades of experience in commercial, residential and industrial building maintenance and construction. He has been certified in refrigerant recovery, recycling and transition. Goodwin has been the author of numerous home improvement articles from 2008 to the present.