Entirely wrong, I'm afraid. Power meters give a realistic calculation of calories burned. Were I to be burning 120 kcal per mile, which is the implication of what you are suggesting, then that would amount to an expenditure of 1800 kcal per hour when merely idling along at 15mph. And the implication of that would be a weight loss of approximately one pound for every two hours of cycling. I wish it were so, but it emphatically is not.

About 30 kcal per mile is a reasonable rough estimate.