http://www.aaa3.net/how-to-scale-trailer/

How many calories do I burn while cycling and towing a trailer?
I can find calculators that tell you how many calories you burn while cycling, but none while towing a trailer. After an 11 mile ride today, I weighed all my equipment.
Fully dressed and equipped, I scaled in at 185 & my bike at 34 lbs. I was towing a trailer that also weighed 34 lbs and my son weighed 38 lbs.
So not only was I moving myself and my bike (220 lbs) but pulling another 72 lbs (total moved weight = 292 lbs!).
Any way to quantify the overall calorie burn per minute or hour?
You need to add the weight of the trailer to your weight, as well as the weight of the bike.
RC 1/5th scale trailer