You are converting energy more efficiently. 

In our homes, energy is converted from one form to another, usually to do work for us, and/or entertain us, and/or to make us more comfortable.

We convert electricity to light our homes and yards; we convert electricity to air-conditioning; we convert natural gas to heat our water; we convert electricity to operate a television; we convert electricity to charge our cell phone battery; we convert electricity to do our wash..

Energy costs money. At times, we have to decide just how much money we will spend for comfort, for entertainment, and to do our work.

The more efficient the make our conversion of energy, the more work energy can do for us, the more it can entertain us, and the more comfortable energy can make us.