How does a grow light work? Useful selection criteria

A grow light provides light for plants. Choosing one means distinguishing power consumption, spectrum and the light that actually reaches the growing area.

Watts, lumens and horticultural measurements

Watts describe electrical power, not the light reaching a leaf. Lumens describe light according to human visual sensitivity. Read a product’s PPFD maps alongside their measurement distance, coverage area and setting; do not use a universal lux-to-PPFD conversion.

Distribution and mounting

Optics, position and area affect coverage. A “full spectrum” label does not prove that a light provides UVB or can heat a terrarium. See the guide to LEDs, UVB and heat for these different functions.

Choose the right setup

The reference guide for indoor plants and the use-based comparison help structure your choice. Browse plant lights for product details and use the energy-use calculation guide to estimate electricity costs.

Editorial review: 3 October 2026 · TerraLED. Set up your equipment according to its instructions and the needs of the species.