Boilers with higher efficiency ratings provide better value because they lower your fuel usage allowing you to save money on your energy bills. Boiler efficiency is measured by evaluating the heat output the boiler generates vs the input energy required to generate that heat. Typically half of your annual energy bills can be attributed to boilers, and property owners will see substantial reductions in their heating costs by upgrading from a low efficiency, such as an 80% thermal efficiency boiler, to a high efficiency boiler rated 95% efficient or higher.