Q. Does boiler excess air reduction really save us on natural gas costs? How much savings can we expect? A. You first need to make sure what the excess air amount is. Before I suggest anything on the boiler excess air, you need to ensure that the boiler load is matched at the proper firing level and that the boiler is cycling is not excessive (i.e. properly sized boiler). There are also so many other questions such as is the boiler properly sized for the load, was it commissioned when originally installed (if the boiler wasn’t adjusted for the load then it could be consuming as much as 30% fuel than it should)?, has there been any significant changes to load? Do you feel that the facility still need that type of steam or hot water production? Does the load vary significantly? Etc.. etc.. Having said all that all boilers should operate at the optimum excess air level. Please contact your licensed boiler service company for a further determination.