Solar Meter vs Spectrometer: Why Red Light Irradiance Claims Are Inflated

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Cheap solar power meters often read red and near-infrared LEDs at roughly twice the value a calibrated spectrometer measures. That is the main reason seller irradiance claims of 150–200+ mW/cm² look so much higher than the 70–100 mW/cm² that spectrometer-tested panels report at 15 cm.

Same panel, two instruments

Some brands publish both numbers. They show the gap clearly:

Panel Solar meter Spectrometer / lab Distance Source (brand data, as of Oct 2026)
MITO LIGHT Expert 5.0 140 mW/cm² 80 mW/cm² 15 cm mitolight
MITO LIGHT Biohacker 5.0 145 mW/cm² 82 mW/cm² 15 cm mitolight
MITO LIGHT Mitohacker 5.0 165 mW/cm² 90 mW/cm² 15 cm mitolight
BlockBlueLight PowerPanel MEGA 167 mW/cm² 89 mW/cm² 15.2 cm blockbluelight
Mito Red Light MitoMAX >155 mW/cm² >70 mW/cm² 6 in (15.2 cm) mitoredlight
Mito Red Light MitoPRO 300X >130 mW/cm² 38.2 average / 55.9 peak mW/cm² (ISO/IEC 17025 lab) 15.24 cm mitoredlight

In these examples the solar-meter figure is about 1.75 to 2.3 times the spectrometer or lab peak figure, and about 3.4 times the MitoPRO 300X lab average.

Why solar meters read high

  • They are built for sunlight. A solar power meter like the Tenmars TM-206 is calibrated for the broad spectrum of the sun, not narrow LED bands.
  • Their sensor isn't flat across wavelengths. The silicon sensor responds differently at 660 nm than at 850 nm. Without a correction factor for each band, the reading drifts.
  • Corrections are specific. GembaRed compared a TM-206 with an external optical lab: a raw reading of 100 corresponded to 48.8 after correction, with separate factors for red, near-infrared and both together. Those factors don't transfer neatly to other meters or panels.

Other ways a number gets inflated

  1. Distance. A figure "at 0 cm" or "at the LED surface" is far higher than at 15 or 30 cm.
  2. Centre point only. The middle of a panel reads higher than the average across its surface.
  3. Cold LEDs. LEDs give more output at switch-on than after 10–30 minutes, when they are warm.
  4. Narrow lenses. Tight beam angles raise the centre reading but leave hot spots and weaker edges.
  5. No method stated. If the instrument, distance and conditions aren't named, the number can't be checked.

Independent testers report the pattern too: Outliyr (June 2026) found manufacturer claims typically 40–70% above spectrometer readings.

How to read an irradiance claim

Ask the seller for:

  • The instrument: brand and model, spectrometer or solar meter.
  • The distance in cm.
  • Centre reading and average over the surface (a 9-point grid is common).
  • Red only, near-infrared only and both together.
  • Whether readings were taken after warm-up.
  • The full report or raw data, not just one number.

A claim with all six is checkable. A big number with none of them isn't.

Our commitment

We don't publish an irradiance figure for Rubrawell panels yet. The manufacturer's listing doesn't include a spectrometer report we can verify, so we won't repeat its numbers. Instead we will:

  • measure each size with a calibrated spectroradiometer, naming the instrument;
  • publish values at 15, 30 and 45 cm, centre and multi-point average;
  • report red only, near-infrared only and combined;
  • measure after warm-up and state the conditions;
  • publish the raw data alongside the summary.

When the measurements are published, we will add the date, lab and instrument here and on each product page.

Sources

  • MITO LIGHT spectrometer and solar-meter figures: mitolight brand site, as of Oct 2026.
  • BlockBlueLight PowerPanel MEGA figures: blockbluelight brand site, as of Oct 2026.
  • Mito Red Light MitoMAX and MitoPRO 300X figures: mitoredlight.com product pages, as of Oct 2026.
  • TM-206 vs optical lab comparison: GembaRed, published study page, seen Oct 2026.
  • Manufacturer claims vs spectrometer: Outliyr light therapy testing methodology, June 2026.

Last updated: 16 October 2026. The Rubrawell team.

Questions

Are solar power meters accurate for red light panels?
Not without correction. They are calibrated for sunlight, and published side-by-side figures show them reading red and near-infrared LEDs about 1.75–2.3 times higher than a spectrometer.
What irradiance is realistic for a red light panel at 15 cm?
Spectrometer-tested panels from EU and US brands report roughly 70–100 mW/cm² at about 15 cm (brand data, October 2026). Claims far above that usually come from solar meters or zero distance.
Why don't Rubrawell pages show mW/cm²?
Because we haven't measured our panels with a spectrometer yet, and we won't repeat unverified seller numbers. We will publish our own measurements at 15, 30 and 45 cm.
Is the "W" rating the same as light output?
No. Watts describe electrical power. Light reaching you is irradiance in mW/cm², which depends on LED efficiency, lenses and distance.
What is the difference between peak and average irradiance?
Peak is the highest single reading, usually at the centre. Average is taken across several points on the surface and is lower. Both are useful; average tells you more about coverage.
Can I measure my panel at home?
You can track relative changes with a solar meter at a fixed distance, but absolute numbers need a calibrated spectroradiometer or a correction factor for your exact meter and wavelengths.