Solar energy is broadly defined as the total energy that the sun radiates through visible light and other unseen electromagnetic waves. Solar energy systems refer to any technology that converts the sun’s energy into another form of energy, such as heat or electricity. Solar energy includes passive solar systems, solar thermal systems for water or space heating, and solar power.
Solar power is a a subset of solar energy, a more narrow term that typically refers to the conversion of the sun’s rays to electricity. The two main kinds of solar power systems are photovoltaic (PV) systems, which convert sunlight to electricity directly with a semiconductor material, and concentrated solar power (CSP) systems that first convert sunlight to heat before using the heat to generate electricity.