Mid-efficiency furnaces are being phased out in Ontario. After 2009, these will no longer be available. While high-efficiency systems are great, they can be difficult to install in some homes, due to venting requirements.  Mid-efficiency furnaces are less complex and less expensive than high-efficiency furnaces. Replacement of an older conventional or mid-efficiency furnace in 2009 with a new mid-efficiency may make sense for many homeowners.