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Guide

How to Choose a Solar Irradiance Meter

An irradiance meter is the other half of every solar test: it says how much sun the panel had when you measured it. The choice is between a cheap pocket meter that is adequate for comparisons and a commissioning instrument that adds temperature, tilt and compass for reports.

By the Akermin Editorial Team · 3 min read

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Choose a solar irradiance meter with a silicon sensor (a reference cell or filtered photodiode) so it responds to the same spectrum a panel uses, a range to at least 1,200 W/m² (1,500 for reflective or high-altitude sites), stated accuracy of ±5 percent or better, and a sensor head that reads correctly at an angle (cosine-corrected) with a way to hold it in the plane of the array. For commissioning, add panel temperature (external probe), a tilt sensor and compass, and logging. Pocket meters (TENMARS, DANOPLUS class) suit DIY comparisons; the Fluke IRR1 and Seaward Solar Survey class suit reports.

Sensor type

Sensor Responds to Best for Notes
Silicon photodiode with diffuser Roughly the PV spectrum Handheld panel checks Cheap; accuracy depends on filter and calibration
Silicon reference cell Matched to crystalline PV Commissioning, performance ratio Tracks panel response closely; often with temperature
Thermopile pyranometer Full spectrum, 300 to 2,800 nm Weather stations, research The reference instrument; slow; costly

For deciding whether a panel is performing, the silicon types are the right match. See what solar irradiance is.

Specifications

  • Range: 0 to 1,200 W/m² minimum; 2,000 W/m² on some meters covers cloud-edge enhancement and snow reflection.
  • Resolution: 1 W/m².
  • Accuracy: ±5 percent or ±10 W/m² for field use; ±2 to 3 percent with certificate for reports.
  • Cosine response: a diffuser dome so angled light is weighted correctly; matters when the sun is not square to the sensor.
  • Temperature: ambient built in; external probe for panel back temperature, which the performance calculation needs.
  • Tilt and compass: to document plane of array and to set the meter to the panel angle.
  • Units: W/m²; BTU/(ft²·h) on some.
  • Hold, max/min, averaging: irradiance flickers under cloud.
  • Logging: for a day’s profile or for commissioning records.

Using it

  1. Hold or mount the sensor in the same plane as the panel, same tilt and azimuth.
  2. Take the reading at the same moment as the panel measurement; under broken cloud, take both several times and pair them.
  3. Note panel temperature for the correction.
  4. Expected panel power = rating × (irradiance ÷ 1,000) × temperature factor. See solar irradiance vs panel output.

Picks

Use Choose
DIY panel checks and comparisons Pocket meter with ±10 W/m² accuracy, hold and max (TENMARS, DANOPLUS, AquaHorti class)
Installers doing performance checks Meter with external temperature probe and tilt (Fluke IRR1)
Commissioning and reports Reference-cell instrument with logging and calibration certificate (Seaward Solar Survey class)

Calibration

Silicon sensors drift slowly and their filters age; check yearly against a reference or a known clear-sky value (a clear noon at sea level in summer gives about 1,000 W/m² on a surface facing the sun). Meters with certificates state a recalibration interval. See how to read a calibration certificate.

Pair the irradiance meter with a PV tester; see how to choose a solar PV tester and best solar panel testers.

Fluke IRR1 Solar Irradiance Meter

Fluke IRR1 Solar Irradiance Meter

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Solar Power Meter, 2000 W/m² Range Handheld Solar Irradiance Meter with Dual Units, MAX/MIN Tracking, Data Hold, Manual Zeroing, Digital Sun Meter for Solar Panel Evaluation and Site Testing

Solar Power Meter, 2000 W/m² Range Handheld Solar Irradiance Meter

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Solar Power Meter Digital Solar Meter, Solar Irradiance Meter for Solar Energy Testing, Solar Transmission Meter with Accuracy Drift<1.5%/Year&Btu/(ft2-h)& W/m² Units for Meteorology Sun Measurement

Solar Power Meter Digital Solar Meter, Solar Irradiance Meter for

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Products shown because their documented specifications fit this guide. Price and availability are on Amazon and can change.

Frequently Asked Questions

What is the difference between an irradiance meter and a pyranometer?

A pyranometer measures total solar energy across the spectrum with a thermopile; it is the meteorological reference. A handheld irradiance meter uses a silicon cell or photodiode that responds like a PV panel, which is what you want for comparing panel output with available light.

How accurate does an irradiance meter need to be?

±5 percent or ±10 W/m² is adequate for panel comparisons and fault-finding; ±2 to 3 percent with a calibration certificate for commissioning and performance-ratio calculations.

Should I measure irradiance horizontally or in the plane of the panel?

In the plane of the panel, tilted and oriented the same way, so the reading is the light the panel actually receives. A tilt sensor or bubble level on the meter helps.

Affiliate disclosure: Akermin earns a commission from qualifying Amazon purchases made through links on this page. Our editorial picks are based on documented specifications and owner feedback, not commissions.