When purchasing a gas furnace, you generally have two paths: buying (the traditional "full-service" route) or buying the equipment yourself online or from a retailer and hiring a pro for the installation. 1. Full-Service HVAC Contractors

Buying online can save thousands in upfront equipment costs, but many contractors refuse to install units they didn't sell themselves.

ARA Heating & Air Conditioning : 27 years in business; specializes in NATE-certified installations.

HVACDirect.com : Carries brands like Goodman, Trane, and ACiQ . AC Direct : Offers wholesale pricing and free shipping. OnlineSupply.com : Specializes in Goodman furnaces. 3. Big Box Retailers