High efficiency furnaces are generally more expensive to purchase when compared to a low or mid-efficiency model of a similar size. A furnace with an efficiency rating of 80 percent, for example, could cost around $1000 less when compared to a furnace with a 90 percent efficiency rating.
Other costs that are associated with a high efficiency furnace, such as installation, can also be higher. Older homes may also require some retrofitting to make existing plumbing or ventilation compatible with a new high efficiency furnace model. These units, however, can provide significant energy savings over its lifetime, allowing owners to recoup their initial costs from reduced utility bills.