I just checked my bike computer for yesterday's easy commute.
15.8 mph, so close to the correct speed.
403 kJ per hour measured at the rear hub.
Humans burn about 1.1 calories per kJ work on the bike.
403*1.1 = 443 calories per hour *moving time*
1.5 hours * 443 cal/hr = 665 calories for round trip.