"Is there any NET change. Most likely and increase in total cost and energy if you really looked at it. It depends on the cost of this trailer. A 36% reduction in fuel costs, for semi-trailer trucks, is a significant amount of money. For every 8.8 miles of driving, .369 gallon of fuel is saved. So, for every 1000 miles, 113 gallons of fuel saved, at $5 per gallon, $209 per thousand miles, or about 21 cents per mile savings. At an average of 45,000 miles per year, that is a savings of $4,309 per year. We cannot know if there are overall savings unless we know the cost and operating cost of the units."For a true cost/benefit analysis, you also need to factor in the embodied energy of the equipment and disposal costs.