Short answer: Irradiance — measured in mW/cm² — is how much light energy reaches your skin at a given distance. It is the single most useful number for comparing panels, but only if it is measured honestly at a stated distance.
What irradiance measures
mW/cm² tells you how much light lands on each square centimetre of skin. Higher numbers mean more intensity, which mainly affects how long a session needs to be — not necessarily a better result.
Why distance matters
Light spreads out as it travels, so intensity drops with distance. A figure measured touching the panel looks huge but is meaningless for real use. A figure measured at a realistic distance — for example, 15cm — reflects what you actually get. Always check the distance a number is quoted at.
How much do you need?
For home use, a realistic figure in the region of 40–100 mW/cm² at 15cm is effective. Chasing ever-higher numbers mostly just shortens session time.
How to spot inflated claims
No distance stated? Treat the number with caution. A figure measured “at the surface” (0cm) is not usable in practice. And look for independently or spectrometer-tested figures — Dermfix RLF panels publish spectrometer-tested output at 15cm (82–92 mW/cm²) on each product page.
FAQ
What is a good mW/cm² for a home panel?
Roughly 40–100 mW/cm² at a realistic 15cm distance.
Why do some brands claim huge numbers?
Often because they measure at the surface (0cm) rather than a usable distance. Always check the distance.
Is higher always better?
No — beyond a point it mainly shortens session time rather than improving results.