When you plug in or hook up a new appliance, behind the wall, down the wire, is a power plant. That power plant will have to burn more fuel to generate the extra electricity you will use and the exhaust products from that extra fuel adds to air pollution and global warming. Most of this electricity was used by major household appliances in our homes and apartments. Additionally, as you and your neighbors add more and more new appliances to the system, the power plant cannot handle the new load and another power plant has to be built. When this has to happen depends, in part, on how many new appliances are bought and the efficiency of each.
Efficient appliances are good for consumers and the environment.
By themselves, they won't solve our energy woes, but they are an important step in the right direction.