Light gathering in M43 vs FF

BSweeney wrote:

Same ISO, Same FOV, Same transmittance of the lens, same exposure.

If you want to use the sensor to generate electricity, as a very expensive solar cell, the Full-Frame sensor will generate more electricity. Easier to buy a solar cell at Radio Shack for that purpose, and use the camera for photography. For that purpose: the size of the sensor is irrelevant.