Brand ratings don't exist for central air-conditioners or furnaces because variables such as home size, climate and insulation make it to difficult to produce reliable ratings for these products. Publications such as Consumer Reports provide advice on purchasing furnaces and central-air systems, but don't give product ratings or comparisons.
Consumer-Search Web site, an aggregator of product reviews on the Web, gives an overview of what buyers should consider when purchasing a central-air conditioner or furnace and explains why consumers won't find brand ratings for these products.
Consumer Reports does not have a nice list of recommended furnaces and air conditioners like it does for other products for the reasons mentioned above. The Web site does provide a list of products it has never tested and an index of products ratings that are no longer current on their Web site.
Remember, you have to pay for product ratings from the Consumer Reports Web site, but you can get reports for free through the Library's subscription to Consumer Reports online. All you need is a library card and PIN.