We live in Orange County, California (mild climate) and need a new gas furnace, with 80% efficiency. Our old one is probably 70-80% (has igniter, metal duct) Will we need larger cold air supply when we switch? Is there a model that comes on quieter and then goes to higher blower setting? Our present Carrier is too noisy.

The variable speed model is a bit quieter BUT after the warranty is over the motor and controls if proven defective cost big $$$$. Go for the 95+ percent unit.

Thank you for the tip, hvac1000; is the 95% better because its motor and controlsare better? Generally, will the new furnace require larger cold air return; our present one is 192 sq. in.of room air and a larger opening in the subfloor.