Energy input and heat in the "thermodynamic system", versus energy output and heat remaining stays in balance. If energy input (in electric current) is higher

Energy input and heat in the "thermodynamic system", versus energy output and heat remaining stays in balance. If energy input (in electric current) is higher than energy output, then heat is added to the system. If energy input is lower than energy output, then heat is lost from the system. All it takes is the ability to channel some of the light (energy output) away from the reservoir of heat to show that the reservoir of heat will decrease. Ultimately you'd expect a temperature gradient at the system boundary to start transferring heat back into the system. through the first law of thermodynamics.