I really don’t care how many watts it consumes as long as i can keep a stable temperature of 37 degrees C.
Watts are a measure of energy (heat) and a resistor dissipating 100W will put-out the same amount of heat as a 100W light bulb.
Power (Watts) = voltage x current
Power = voltage2/R
Power = curren2 x R
Of course, the actual temperature is not as easy to calculate - A small insulated box will get hotter than a large insulated box. You can’t warm-up a room with a 100W light bulb.
And, you get a certain heat rise so without feedback (a thermostat), if the ambient temperature changes by 1 degree, the internal “37 degree” temperature will also change by 1 degree.