Will the company offer an ARI Certified combination? The Air-conditioning & Refrigeration Institute certifies product efficiency. If you are replacing your air conditioner or heat pump, a reputable contractor will present you with a certification of performance from ARI. Without replacing the condensing unit (outdoor unit) and the evaporator (air handler or indoor unit), a contractor cannot promise you will receive the efficiency you pay for, or even that the system will operate correctly over time. Will the contractor permit equipment replacements? If you replace your heating or cooling system, you should insist that the job is permitted. When jobs are permitted, a municipal inspector will review the installation to ensure the job can at least meet current building codes. Like licensing, building codes are the minimum standard. Is the company willing to provide references? If you do not know anyone who has done work for a company, ask for references. The contractor should be willing to provide you with three to five recent customers you can call. Will the company provide you with a copy of a "load calculation?" A load calculation is a method of sizing equipment. It’s often called a “Manual J®” for the Air Conditioning Contractors of America's Manual J®, the standard for sizing residential equipment. Once measurements are taken, load calculations can be conducted quickly using computers. Contractors should be able to show and review the load calculations and provide you with a copy if you authorize the company to proceed with the replacement.