What do you want the air conditioner in your house to do? That’s an easy question to answer—you want it to keep your house cool when it’s hot outside. But if your air conditioner drains a huge amount of energy doing that, much more than it should, it’s not doing its job the best way it can.
This is where efficiency comes in. An efficient air conditioner is one that maximizes how it converts electrical power into cooling power. You may have an AC that’s effective at giving you cooling but still be highly inefficient.