Comparing 80% to 97% Efficient Furnaces

When considering your next furnace purchase, here are some purchase payback comparisons between a 97% Efficient, 2-Stage, Variable Speed Furnace and a standard 80% efficient, single stage, single speed furnace.

Cost: The installed price of a 97% Efficient 2-Stage, Variable Speed furnace may initially cost $1400 – $1500 more than an 80% efficient model, BUT…

A 97% Efficient, 2-Stage, Variable Speed furnace operates on low stage the majority of the time. Here are 3 reasons that’s important:

  1. Longer periods of low speed fan operation keeps the air moving and circulating. Comparing that with the 80% furnace running for shorter periods of time but on high speed means that the slow, almost continuous, circulation warms or cools the air evenly, even in the dead spots in the corners of the rooms making the whole house more comfortable, and it’s operation is quieter too.
  2. Older 80% furnace models had one fan speed – High, so resistance and back pressure builds up quickly in the duct system and this is especially true if the installed ductwork was undersized thereby restricting airflow and ultimately reducing energy efficiency.
  3. This one is important! A Variable Speed 2-Stage furnace can almost eliminate an undersized duct problem because it operates on low speed the majority of the time so the low speed operation does not exceed the ductwork airflow capacity. It will operate on high due to an immediate demand such as a door being left open longer than necessary (kids will be kids) but as soon as demand is satisfied, it ramps right back down to low speed.


This is a unique website which will require a more modern browser to work! Please upgrade today!