T8 vs T5 Tube Lights: Which Is Better for Plants?

What are T8 and T5 tubes?

T8 and T5 are names for fluorescent tube sizes. The number after the T refers to the diameter in eighths of an inch: a T8 tube is 1 inch across, and a T5 tube is 5/8 inch across. These are standard sizes used in many indoor lighting fixtures, including shop lights and under-shelf lights.

When you see T8 or T5 on a grow light listing, it tells you the tube shape and size, not the light output or spectrum. Two T5 tubes from different makers can have different wattages and coverage areas. The listing title and bullet points are where you read those details.

Fluorescent tubes have been used for indoor plants for a long time. The University of Minnesota Extension notes that many types of artificial lights are available in different styles and sizes to fit your needs and budget. T8 and T5 tubes are one option among many. For a modern alternative, see our guide to LED grow light strips.

Size and mounting compatibility

The main difference between T8 and T5 is the tube diameter, which affects the fixture you need. A T8 tube will not fit a T5 fixture and vice versa. Before buying, check the listing to see what fixture the tube is made for, or whether the tube comes with its own housing.

Many T5 and T8 grow lights are sold as complete fixtures with a reflector and a power cord. Some are designed to hang from a ceiling or shelf, while others sit directly on a shelf. The listing will say what mounting hardware is included, such as hangers or clips.

If you already have a fluorescent fixture, you need to match the tube size. If you are buying a new light, you can choose the size that fits your shelf or rack. For a seed starting rack, a 2-foot or 4-foot tube length is common, but the exact length is stated on the listing. Learn more about mounting options for grow lights.

Efficiency and wattage

Efficiency in lighting means how much light a fixture produces for the electricity it uses. T5 tubes are often described as more efficient than T8 tubes of the same length, but the actual efficiency depends on the specific model. The listing may state the wattage of each tube, and that is the number to compare.

When you read a listing, look for the wattage of one tube, not the total for a pack. A pack of 4 tubes at 20 watts each draws 80 watts total. The listing will say whether the wattage is per tube or for the whole pack. For more on reading wattage, see wattage vs actual light output.

The DesignLights Consortium, a lighting program, verifies the performance and efficiency of horticultural lighting products. You can check their Qualified Products List for energy-efficient options, but the site does not provide specific efficiency numbers for the models in its guides.

Spectrum and light quality

Plants use light in the photosynthetically active radiation (PAR) range, which is roughly 400 to 700 nanometers. Fluorescent tubes emit light across this range, but the exact spectrum depends on the phosphor coating inside the tube. Some tubes are labeled as 'full spectrum' or 'daylight,' which means they emit a broad range of colors.

The listing may mention a color temperature, such as 5000K or 6500K. A higher Kelvin value looks whiter or bluer, while a lower value looks warmer or yellower. For seedlings and leafy greens, many growers prefer a cooler white light, but the best choice depends on your plants and the stage of growth. Understand more about color temperature in grow lights.

The University of Minnesota Extension explains that plants need light for photosynthesis, and that too little light can make plants leggy. The light quality from a tube is one factor, but the intensity and duration also matter. The listing will not state PPFD or DLI, so you cannot compare those numbers directly. Learn what PPFD and PAR mean.

T5 vs LED strips

LED grow light strips are a modern alternative to T5 and T8 fluorescent tubes. LED strips are often thinner, more energy-efficient, and may have a longer lifespan. They come in similar lengths, such as 2 feet and 4 feet, and can be linked together to cover a shelf.

If you are comparing T5 tubes to LED strips, look at the wattage and coverage area on each listing. LED strips often have a lower wattage for the same length, but the light output may be different. The listing will state the coverage area in square feet, which helps you decide how many you need. See our best LED grow light strips for options.

For a seed starting rack or a shelf of houseplants, both T5 tubes and LED strips can work. The choice depends on your fixture, your budget, and the stated details on the listing. Read the maker's manual for mounting instructions and safety guidelines. Compare with LED grow light bars if you need wider coverage.

What to check on a listing

When you compare T8 and T5 tube lights, check these details on the listing: the tube size (T8 or T5), the wattage of one tube, the length in feet, the coverage area in square feet, whether it is dimmable, and whether it has a timer. These are the facts you can compare.

Also check what is included in the box: the tubes, the fixture, the power cord, and any mounting hardware. Some listings sell tubes only, while others sell a complete fixture. The listing will say.

If a detail is missing, such as the coverage area, the seller may not state it. In that case, you can contact the maker or read the maker's page for the model. The site's guides compare lights on stated details only, so a missing detail means it is not part of the comparison. For a full list of options, see our best LED grow lights.

What to pick for your job

Questions

Can I use a T8 tube in a T5 fixture?

No, T8 and T5 tubes have different diameters and are not interchangeable. Check the fixture's label or the listing to see which tube size it accepts.

Are T5 tubes better for plants than T8?

T5 tubes are often more efficient, but the best choice depends on your fixture and the specific model. Compare the wattage and coverage area on the listing.

Do T8 and T5 tubes provide the right spectrum for plants?

Fluorescent tubes emit light in the PAR range, but the exact spectrum varies. Look for tubes labeled 'full spectrum' or 'daylight' for a broad range.

How many T5 tubes do I need for a seed starting rack?

The number depends on the coverage area of each tube and the size of your rack. Check the listing for the coverage area in square feet and plan accordingly.