The LED bulbs will physically fit into the 4-foot-long fluorescent fixtures. However, the ballasts will ruin new straight-LED bulbs. Some LED bulb manufacturers offer bulbs that can work with the ballast in place, but they are less efficient and more expensive. 

Here are the steps we took to replace our old T-8 linear fluorescent bulbs in an older kitchen fixture:

 Remove the ballast

Step 1: Be Safe

Turn off the electricity. The “lock-out, tag-out” approach is safest—turn off the breaker that supplies power to that fixture. Tape a note over the breaker that explains you are working on a fixture and to keep the breaker off. Inform other people in the house what you are doing. Also make sure you wear eye protection—this is especially important should an old fluorescent bulb shatter while you are removing it.

Step 2: Remove the Bulbs

You may need to remove a fixture cover to expose them. In some states, fluorescent bulbs are considered hazardous material. They contain mercury, and should not be thrown in the trash but must be taken to a disposal center (some hardware stores serve as drop-off points). See bit.ly/lamprecycle for regulations in your state.

Step 3: Remove the Ballast

Remove the cover(s) from the ballast and wires and unscrew the ballast from the unit. Remove the ballast from the fixture wires, leaving enough of the black (typically “hot” or energized) and white (typically neutral) wires from the center to reach the socket wires. We threw the old ballasts in the trash. There are no regulations regarding their disposal and no recycling programs available for them.

Step 4: Rewire

Next, connect the fixture and socket wires together, then replace the wiring cover. The most straightforward way to rewire the fixture is to twist the wires together with the properly sized wire nuts. In our case, there were two yellow wires on the left side; and two reds and two blues on the right side. Regardless of the colors, the important thing is to put all the wires from one side together securely with one of the leads from the center (i.e., the incoming circuit wires), and all of the wires from the other side together with the other lead.

Some replacement LED tubes are made with both the hot and neutral connection on one side. In that case, you’ll need to rewire the sockets and follow the LED bulb manufacturer’s instructions.

Step 5: Install LEDs

Take the LED bulbs out of their packaging, peel off the protective plastic, and remove the tip guards. Install the bulbs as you would a fluorescent T-8, inserting each end into the slots and twisting to lock each into the receptacle, with the LED string facing down. All bulbs should be tightly seated.

Step 6: Try It Out

Return to the breaker box, remove your note, and turn on the breaker. Test the light and replace the cover, if your fixture has one.

Let There Be Light

If in the future someone mistakenly installs fluorescent bulbs into the fixture, the bulbs won’t work, but won’t be harmed. It’s a lot like what happens when the ballast dies on an old fluorescent fixture—no light. Just in case, consider placing a sticker on the wiring cover noting that the fixture is wired for LED only and has no ballast.

We tested a new two-bulb fixture fresh from the store with the old T-8 fluorescents and with the new LED bulbs. The fluorescents, despite being rated at 32 watts, drew 45 W each, while the LED bulbs (rated at 20 W) drew 19.9 W each. We typically run the lights four hours per day, 365 days a year, and our electricity costs us $0.17 per kilowatt-hour. In this case, our annual savings will be $6.23. Our LED bulbs cost $12 each, so it will take a couple of years to recover the cost of the replacement.

The light quality in the kitchen is very good—the bulbs provide the same amount of light as the old fluorescents, but with a nicer color cast and no flicker. The lights take about 1 second to come on fully.