Condensing boilers continue to grow in popularity across Canada, due in large part to their high energy efficiency. Many models offer about 90 per cent thermal efficiency, although some are rated as high as 98 per cent. The efficiency with which these boilers burn gas or oil compares very favourably to the 70-80 per cent ratings offered by traditional, non-condensing boilers. System design and installation are key to maximizing energy savings, so a comparison of what local contractors can offer is advisable.