BOILER INSTALLATION COSTS. If you’re replacing an old boiler, expect boiler installation costs for mid-efficiency system to cost about $2,500 to $4,000 (80 percent efficiency), and boiler installation costs for a high-efficiency system to cost between $5,000 to $9,000 (90 to 97 percent efficiency).owever, there are other factors that could swing boiler installation costs higher or lower. 1  You may need a new chimney liner if you’re upgrading to higher efficiency boiler. 2  Generally, this costs about $300 to $700 for gas and $700 to $1,800 for oil. 3  Removal of the old unit can range from $300 to $1,500 or more.