Grow Light Bulb vs Panel: Screw In Bulbs or Full Fixtures

The short answer

Grow light bulb vs panel comes down to how much space you need to cover. A screw in LED grow bulb fits a standard lamp and lights one or two plants. A panel or bar fixture covers a whole shelf or tent with more even light. Bulbs suit single pots, and panels suit trays and shelves.

Both use LEDs, but they suit very different jobs.

What is a screw in grow bulb?

A grow bulb looks like a regular light bulb. It screws into a standard socket in a desk lamp, clamp lamp or ceiling fixture. Inside, a set of LEDs gives off light plants can use.

The US Department of Energy page on LED basics explains that LEDs make light efficiently and send it in a specific direction. That is why a grow bulb lights a focused spot below it.

Bulbs are cheap and easy. You can add one to a lamp you already own. They work well for a single houseplant, a small herb pot or a seedling or two.

What is a grow light panel?

A panel is a flat fixture with many LEDs spread across a board. Bars are long strips of LEDs mounted side by side, and both hang above plants and light a wide area.

Sources: US Department of Energy, University of Maryland Extension, University of Vermont Extension.

Panels give more even light across a space. Plants at the edges get closer to the same light as those in the center. That matters when you grow trays of seedlings or several plants at once.

The University of Vermont Extension tips for choosing grow lights covers fixture types and how to match them to the plants you grow.

Our post on grow lights for cannabis explains fixture types for larger spaces.

Which light color should you pick?

Both bulbs and panels come in white or in pink and purple blends. The University of Maryland Extension article on fine tuning your indoor plant lighting choices explains that white LEDs give a broad spectrum that works well for most home plants.

White light also lets you see your plants in true color. That makes it easier to spot problems on leaves. In a living space, white light is easier on the eyes.

Our post on choose the right LED lights for your cannabis grow covers spectrum choices in more depth.

How close should each type sit?

Bulbs send light in a focused cone, and most work well within about a foot of the plant. Farther away, the light spreads and weakens fast.

Panels can sit a little higher because they cover more area. The right height depends on the fixture’s power. Check the maker’s guide and watch the plants.

Our post on LED light distance cannabis explains how to judge distance by plant response.

When should you upgrade from bulbs to a panel?

If you add more plants, a bulb won’t be enough. Several bulbs in a row can work for a shelf, but a single bar or panel often costs less in the long run and spreads light better.

If your plants stretch even with a bulb close by, they may need more light than a bulb can give. A panel gives more total light from above.

Do bulbs and panels last as long?

Both use LEDs, which can run for many thousands of hours. In practice, heat shapes lifespan. Panels often have metal backs or fins that shed heat well. Bulbs pack LEDs and drivers into a small shell, so they can run warmer.

Give bulbs open air. A grow bulb inside a closed shade or a tight fixture may run hot and fade sooner. Clamp lamps with open reflectors work better.

Dust both types often. A layer of dust on the lens cuts light and holds heat.

How to: step by step

1. Count the plants you need to light.
2. Use a bulb in a lamp for one or two pots.
3. Use a panel or bar for shelves, trays and tents.
4. Pick white light for living spaces.
5. Set the fixture at the distance its maker suggests.
6. Run lights on a timer for steady days.

Check the socket rating before using a grow bulb in a lamp. Use a bulb within the lamp’s rated wattage.

Troubleshooting

Plants leaning toward a bulb. It’s off to one side. Center it above the plant.

Edges of the tray stretching. A bulb can’t cover the tray. Switch to a panel.

Leaves pale under a panel. The panel may be too close. Raise it.

Plants stretching under a panel. It may be too high. Lower it.

Hot spot in the center. The fixture is too close. Raise it for more even light.

Matching the light to the space holds plants compact and healthy. Kind Seed Co carries cannabis seeds for growers planning a new indoor setup.

Sources

• LED basics, US Department of Energy, LED basics
• Fine tuning your indoor plant lighting choices, University of Maryland Extension, Maryland Grows, Fine tuning your indoor plant lighting choices
• Tips for choosing grow lights, University of Vermont Extension, Tips for choosing grow lights