Energy efficiency encompasses the policies or practices which help us evaluate the full cost of our energy choices and which help us get more output from a unit of energy. This category includes cogeneration and efficient natural gas-burning turbines, among other technologies. This category includes nearly all electricity-using and thermal technologies, such as motors, lighting, heating, ventilating, air conditioning, and appliances. It also includes technologies that help conserve or better use energy, such as insulation and controls.
Renewable energy includes sources of power that are replaceable and often locally accessible.
Active and passive solar technologies use the sun's energy for cooking, space heating, and water heating. Photovoltaic cells convert solar energy into electricity.