EPA now has the list of approved boilers in a searchable database format. One thing to note when comparing efficiency ratings is most of the boilers in the list are using different test methods. To understand if the efficiency number can be directly measured you would need to research what test method was used for a particular model you are comparing. All the Varmebaronen Vedolux wood boilers were tested with Method 28-PTS.

This is what it looks like if you search for Varmebaronen. Search to see what boilers are currently approved for 2020.