Solar Spectral Irradiance: AM0, AM1.5G, AM1.5D

The American Society for Testing and Materials developed and defined the solar constant 1366.1 W/m2 u (also known as the total sky irradiance) and reference spectrum ASRM E490. This AM0 solar spectral irradiance is based on data from satellites, space shuttle missions, high-altitude aircraft, rocket soundings, ground-based solar telescopes, and modeled spectral irradiance.

The reference spectrum ASRM E173 AM1.5G and AM1.5D provides terrestrial uses in simulating and evaluating photovoltaic device.


The International Electrotechnical Commission (IEC)’s IEC60904-3, a terrestrial standard testing condition of the spectral distribution of the irradiance of AM1.5G, is also frequently used in photovoltaic device measurements.


ASTM E173 and IEC60904-3 AM1.5G reference spectrums are very similar. The difference in total irradiance is 4/10,000. These two are almost identical.


IEC 60904-3 is more common in measurements for terrestrial photovoltaic devices and related realm.


AM1.5G Irradiance is 1000 W/m2 which equals to 100 mW/cm2.


Solar Condition International Standard IPower Density(W/m2)
AM0 ASTM E490 1366.1
AM1.5G/D ASTM G173 1000.4/900.1
AM1.5G IEC 60904-3 1000

AM Irradiance and International Standards.