85% watertube boiler

Joye Chizek

...who answered my previous post trying to understand a new watertube boiler that has 7 sq. ft heating surface to achieve 85% efficiency. While everyone brought up good points, I'm still puzzled. I looked up the new High Efficiency models side by side with old models that were advertised as 83% efficient and the boilers have the exact same jacket dimensions but looking at a 8000 MBH input the new boilers have 1541 sq. ft. heating surface as opposed to 972 and have a shipping weight of 18652 lb. vs. 13459 lb. I would think the factory cost of adding that much steel would have to be reflected in the price. I know oil prices are through the roof but how much is 2% of advertised efficiency (as opposed to realized efficiency) worth to engineers and end user? Thank you...Joye