1. 1.The bahavioural paradigm in which cold-exposed animals can work for pulses of infrared radiation has been extensively used in the literature, but a formula to calculate the amount of heat obtained has not been advanced. 2. 2.This paper describes a computational formula for heat influx in rats: E = 3.64 · 10 −6 · n · d · I · M 0.6 where E is heat influx (kJ), n is number of rewards, d is reward duration (sec), I is irradiance (mW/cm 2), and M is body mass (g).