Chemical actinometry involves measuring radiant flux via the yield from a chemical reaction.
From the en.wikipedia.org
Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux, which includes infrared, visible, and ultraviolet light.
From the en.wikipedia.org
In optics, or radiometry, the term power sometimes refers to radiant flux, the average rate of energy transport by electromagnetic radiation, measured in watts.
From the en.wikipedia.org
The pictures also give information about the total flux of radiant heat from active volcanoes.