HVAC folks have a special language just like any other profession. Unless you are in the business you really are not going to be able to get a truly clear understanding of all of their terminology. That is not a bar to getting a decent price. Many AC vendors are proposing units that exceed the government standards for energy savings. By exceeding the standards they assure you that you can get the $1500.00 tax credit offered by Federal Tax Credit for Energy Efficiency. If you have used the tax credit for any other Energy Star improvement, you can NOT use it again. It is a once and done tax credit, no matter what the salesman tells you. Also remember it is up to 30% of the purchase or a maximum of $1500.00 for most Energy Star improvements. Solar panel installs fall under another category so look that up if you are interested. The tax credit is not a refundable tax credit. That is important. A refundable tax credit means that if you owe no taxes and you generate a refundable tax cre...