Calories burned with and without power meter

Two weeks ago I was traveling for business and rented a bike. Had my Edge 530 and heart rate monitor. Two tempo/sweet spot rides:

  • 2 hours 20 minutes (2.33 hours) @ 1517 calories = 650 calories/hour
  • 2 hours 10 minutes (2.17 hours) @ 1366 calories = 630 calories/hour

Last week on trainer:

  • 630 calories/hour for 60 minutes with 3x10 (30 min) sweet spot
  • 660 calories/hour for 60 minutes with 4x8 (32 min) sweet spot and 16 short sprints (~550W for 5 seconds)

The heart rate only ones seem a bit high on cals/hour. Those rides had average HR around 139bpm and the trainer rides were 3-4bpm higher.

Don’t know if matters, I’ve configured my Edge with correct LTHR and FTP.