What efficiency levels can I expect from a propane boiler?

Several hundred propane boiler models qualify for the Energy Star label. This means that the boilers have an efficiency rating of at least 85 percent, as rated by their AFUE. An 85 AFUE rating is actually just the start, as more than 200 of these boilers are also rated as “Most Efficient” within the Energy Star program — achieving efficiency ratings ≥ 95 percent AFUE.