The cost of a boiler HVAC system depends on several factors, including the size of the system, the type of boiler, and the installation costs. Generally, a boiler system can range from $2,000 to $10,000 or more. Boilers that are larger and more efficient tend to cost more, while smaller, less efficient boilers are usually less expensive. Additionally, installation costs can vary depending on the complexity of the system and the labor costs in your area.