Everything You Need to Know About LED Tube Lights

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Replacing your fluorescent tube lights with LED retrofits can be a confusing and daunting process. We've put together this guide to demystify all of the ins and outs of replacing your fluorescent tubes with LED tube lights.

1) Advantages of LED tubes over fluorescent tubes

The many advantages of LED tubes over fluorescents are covered quite extensively, so we won't go into depth, but the three primary advantages are:

  • Higher efficiency, energy savings (up to 30-50%)

  • Longer lifetimes (typically 50k hours)

  • No mercury

2) Fluorescent tubes sizes and LED tube light retrofitting

Because fluorescent fixtures are often mounted into ceilings and connected directly to mains electricity, they are relatively expensive and difficult to replace completely.

As a result, it oftentimes makes the most economical sense to simply use the same fluorescent fixture, but replace the fluorescent tube with an LED tube light.

Therefore, it is important to understand the types of fluorescent tubes that were developed, so that the correct LED tube light can be retrofitted in place.

Over the years, fluorescent tube manufacturers developed many varieties of sizes and types.

  • T8 4-ft: Four-foot T8 fluorescent lamps are the most commonly used type today. They are 48 inches in length, and have a 1 inch lamp diameter.

  • T12 4-ft: Four-foot T12 fluorescent lamps are less efficient compared to T8 lamps. They are the same length as T8 lamps, but have a larger 1.5 inch lamp diameter.

  • T5 4-ft: Four-foot T5 fluorescent lamps are typically the most efficient, and some of the newest types of lamps introduced in the 2000's in the USA. They are commonly designated T5HO (high output) and provide more brightness than their T8 counterparts. They are slightly shorter than four feet (45.8 inches). T5 lamps come in a variety of lengths such as 1-ft, 2-ft and 3-ft versions and are commonly used in non-ceiling fixtures such as table lamps.

T8 and T12 tubes are also available in other lengths such as 8-ft tubes, but 4-ft lengths remain the most common types.

LED tube lights replicate the mechanical dimensions to ensure that they can be true retrofit replacements, and adopt the same form factor names (e.g. 4-foot T8 LED tube light).

T8 and T12 fixtures are generally the same length and use the same pins, so mechanically they are usually cross-compatible.

T5 fixtures are NOT cross-compatible with T8 and T12 lamps due to their different pin sizes and actual length.

3) Fluorescent ballasts and LED tube light retrofitting

All fluorescent tube lights use a device called a ballast to regulate the lamp's brightness as it warms up. These devices are necessary for fluorescent lamps, and differ from incandescent lamps which can be connected directly to mains electrical circuits.

Fluorescent lamp fixtures typically house the ballast inside the fixture, and is not accessible without removing the fixture from the ceiling. Alterations to the fluorescent lamp ballast should be done only by those comfortable and knowledgeable with electrical work.


T5, T8 and T12 fluorescent lamps operate slightly differently, and therefore have different fluorescent ballast types.

LED lamps, on the other hand, operate differently from fluorescent lamps, and do not utilize a ballast (but do utilize electronic components that make up the LED driver).

Early LED tube lights required removing or bypassing the fluorescent ballast. Now, many LED tube lights are designed to be compatible with fluorescent ballasts, allowing for a simple replacement of the fluorescent tube, without re-wiring the fixture. Below, we discuss the common terms used for each of these configurations.

3A) UL Type A LED tube light - Ballast Compatible

Commonly designed "UL Type A" - these LED tube lights are designed to be compatible with fluorescent ballasts. They are the most straightforward to implement, since it does not require rewiring the fluorescent fixture.

The UL Type A LED tube light essentially behaves the same a fluorescent lamp, and is a straightforward swap-in.

Ideal for: Consumers not comfortable with or preferring to avoid electrical wiring work, lighting installations where electrician labor costs are high

Disadvantages: Fluorescent ballasts can fail, requiring continued maintenance and eventual replacement or bypass of the ballast; potential issues with fluorescent ballast compatibility; lower overall electrical efficiency due to ballast.

3B) UL Type B LED tube light - Ballast Bypass

LED tube lights that have  a "UL Type B" specification are not compatible with fluorescent ballasts. They cannot be used with the fluorescent ballast, and must be connected directly to mains electricity. The LED driver, however, is integrated into the LED tube itself.

UL Type B LED tubes can further be categorized as single-ended or double ended.

In a single-ended configuration, only the two pins on one end of the tube are used (one pin = live; one pin = neutral), and the two pins on the other end are not electrically functional, and only used for holding the lamp in place.

For single-ended configurations, the direction in which a lamp is installed is important - incorrect configurations can lead to a lamp that does not illuminate, or a potentially hazardous fire risk. Single-ended configurations will typically have a sticker label on one end of the tube with the words "AC INPUT" or similar. Some single-ended configurations can accept power from either end.

In a double-ended configuration, the two pins on each side of the tube are the same polarity. Therefore, the lampholders on one end of the tube must be connected to [neutral], while the other must be connected to [positive].

Ideal for: installations where electrical rewiring is an option; higher efficiency and lower maintenance costs.

Disadvantages: requires comfort with and and knowledge of fixture wiring and electrical safety.

3C) UL Type C LED tube light - Remote Driver

UL Type C LED tubes are relatively uncommon, but offer the most flexibility and efficiency for a lighting system. Unlike a UL Type B LED tube, these do not have the LED driver integrated into the LED tube, and therefore requires a separate LED driver device to be connected between the LED tube and mains electricity.

Ideal for: lowest maintenance costs as LED drivers can be replaced without replacing the whole LED tube; more LED driver options such as 0-10V dimming and other IoT connectivity.

Disadvantages: Requires the most electrical work as the fluorescent ballast needs to be removed, then replaced with an LED driver.

3D) Shunted vs Non-shunted Tombstones

Tombstones are the "sockets" or lampholders that the LED tube lights will be installed into, providing both the mechanical support as well as electrical current.

Tombstones have two electrical contacts to match the two pins on a fluorescent/LED tube light. The two electrical contacts can either be:

i) not connected to any electrical source

ii) one connected to live, the other connected to neutral

iii) both connected to live or neutral

Scenario ii) is called non-shunted, while scenario iii) is called shunted. "Shunting" refers to the joining of two separate circuits into one. The result of shunting is that both tombstone contacts connect to the same electrical polarity.

In general, fluorescent fixtures that have never been altered for LED or instant-start ballasts have non-shunted tombstones, while those that have been altered for LED or instant-start ballast may have shunted tombstones.

Sometimes, tombstones are externally shunted, as shown in the photo above, where the wire inputs are only open on one side. In some cases, however, tombstones can be internally shunted, where the wire inputs on both sides are open, but are connected inside the tombstone.

Since some tombstones are internally shunted, visually checking the tombstones does not provide a conclusive result. We strongly recommend testing the two tombstone contacts with a voltmeter to determine whether a closed or open circuit exists. A closed circuit will indicate shunted tombstones.

3E) Determine if your LED tube light is compatible with the shunted or non-shunted tombstone configuration

If your LED tube light is single-ended, it is NOT compatible with shunted tombstones. This is because each of the two contacts in the tombstone must be opposite polarity for a single-ended LED tube light to work. In a shunted tombstone, however, this is not possible as there will be an internal short circuit.

If you have shunted tombstones, you will need to rewire or replace them and connect them to match the single-ended LED tube light manufacturers' wiring diagram.

If your LED tube light is double-ended, it is likely compatible with both shunted and non-shunted tombstones. The reason is that the two pins on each end of the LED tube light expect the same polarity, so whether or not they are shunted should have no influence on the final resulting circuit.

Keep in mind this section discusses whether or not the tombstone itself is shunted vs non-shunted - be sure to connect the wires into the tombstone correctly to match the manufacturers' wiring diagram to ensure safe installation.

3F) What if you don't want to worry about all of this?

Installing the wrong type of LED tube can result in premature failures and potentially dangerous short-circuits and fire hazards.

We recommend looking for LED tubes that are compatible with any of the potential electrical configurations in a fluorescent fixture - for example, Waveform Lighting's T8 3-in-1 LED tubes.

Commonly called 3-in-1 compatible, these LED tubes are compatible with any of the following configurations:

i) Without removing the fluorescent ballast (UL Type A / ballast compatible)

ii) With removing or bypassing the fluorescent ballast (UL Type B / ballast bypass) and shunted or non-shunted tombstones (dual-ended)

iii) With removing or bypassing the fluorescent ballast (UL Type B / ballast bypass) and non-shunted tombstones (single-ended)

4) Photometric specifications for LED tube lights - color temperature (CCT), lumens and CRI

Commonly characterized as the core photoelectric specifications, it's also important that the emitted light qualities are similar or exceed your current fluorescent tube lighting.

Correlated Color Temperature (CCT)

Most fluorescent tube lights have a correlated color temperature (CCT) of 4000K or 5000K, as they have been considered to be most suitable for retail and office environments, respectively. Many fluorescent lamp phosphor developments over the years, however, have enabled a wide range of color temperatures.

Similarly, LED tube lights are also available in a wide range of color temperatures. Generally, the color appearance will be similar between an LED tube light and fluorescent tube light with the same color temperature rating.

Luminous Flux

Luminous flux, measured in lumens, measures the total amount of light emitted from a lamp, and is the best measure to determine the brightness of a lamp.

The best way to make an apples-to-apples comparison is to compare the luminous flux value of the fluorescent lamp with the LED tube light. Generally, a 35W T8 fluorescent lamp emits about 2500 lumens.

One thing to note about LED tube lights is that they tend to direct light downward, rather than a full 360 degrees in a fluorescent lamp. Therefore, when installed in a ceiling fixture, an LED tube light may provide more useful lumens, since the light is directed downwards rather than back into the fixture as in a fluorescent lamp.

Color Rendering Index (CRI)

CRI measures the extent to which objects' color appear true and accurate under a light source. Most fluorescent lamps have a CRI rating of 80 or so, and the majority of LED tube lights also come in at around 80 CRI as well. 80 CRI is acceptable for most applications, but for enhanced color quality and environments where color perception is important, look for a higher CRI rating in an LED tube light.

5) LED tube light costs and financing

Finally, we'll talk a bit about the cost considerations for making an LED tube light purchase. In recent years, LED tube lights have come down in price to a level that competes with fluorescent lamps, so the purchase price of the lamps makes LED tube lights a very appealing option.

If, however, the LED tube light you selected is not a UL Type A lamp, you will incur electrical rewiring labor costs. For a large or commercial installation, these costs may be significant depending on the complexity of the rewiring necessary for the fluorescent fixture. Typically, it can take a trained electrician 15-25 minutes per 4-lamp fluorescent fixture.

If we assume it takes an hour for an electrician charging $100 per hour to complete the rewiring of 3x 4-lamp fluorescent fixtures, we can calculate a labor cost of more than $8 per lamp. You can see how labor costs quickly add to the initial costs of the project - adding to the appeal of UL Type A compatible LED tube lights.

Calculate the amount of electricity and maintenance costs that LED tube lights will save, and determine the payback period. Generally, the shorter the better!

Also, consider the warranty terms of the manufacturer. Ideally, the payback period is shorter than the warranty, as that way, you are insured against any premature product failures that jeopardize the cost savings of going with LED tube lights.