Originally Posted by gregf83

Trust the Strava data. For calculating caloric expenditure you should be looking at total work measured in kJ and multiplying by 1.0 or 1.1 to get calories. Weighted avg power is NP and not useful in calculating calories. I believe Strava uses a factor of 1.12 to go from kJ to calories.

Garmin connect doesn't calculate avg power properly and reports moving avg power excluding zeros which happen when coasting. Their total work seems to be accurate so you could just look at the work in kJ and use that number as calories. I don't know how they come up with the calorie number on their site (probably HR based) but it's not correct.