Calorie counting on TR vs Whoop

Hi all,
I am new to TR so please feel free to suggest any articles or blogs that might have already been discussed to answer my question. My question is essentially: is TR’s calorie expenditure at the end of a workout in your mind accurate? When I compare to what my Whoop says (which is pure heart rate based), Whoop measures calories burned roughly half of what TR says. I am also wearing a Garmin dual HR monitor and surprisingly the HR monitor is very close to what Whoop says my HR is, so I wonder if TR is accounting for power where Whoop is not? Does anyone know of any research that discusses the impact of force on calories burned vs purely HR? Thank you!

This might be of interest/ help (TR blog on the subject): kJ to Calories Conversion: How many calories do I burn cycling?


Calorie burn calculated from a (working/good) power meter is accurate to about 5%. There is more error in estimating calories burned when using HR only.