I recently changed my daily walking routine, because of time restaints. Instead of walking the entire trail, I walk up and down one hill. I did a google search and found this interesting table on calorie burn.
http://www.nutristrategy.com/activitylist3.htm
1 hour activity / calorie burn
Walking 4 mph / 345
Walk uphill 3.5 mph / 518
Carry 15lb load / 302
There was a receent thread on whether you should train with or without a pack. From a calorie burn presective. carring a load doesn't seem all that benificial.