Green Motor or Energy efficient motors use less electricity as they have better design and use high quality materials to reduce motor losses therefore improving motor efficiency.
The improved design results in less heat dissipation and reduced noise output and last longer than other motors of same size.
For example motor used in TDA350 has a efficiency of 87%. This means 87% of electrical input energy is converted into 87% of mechanical energy. The rest of 13% of the electrical energy is converted into heat which is seen with rise in motor temperature.