What is Energy? Published Oct. 5, 2009 By officials at the 86th Civil Engineer Squadron RAMSTEIN AIR BASE, Germany -- Energy is the ability to do work. It comes in different forms -- heat (thermal), light (radiant), mechanical, electrical, chemical and nuclear energy. There are two types of energy -- stored (potential) energy and working (kinetic) energy. For example, the food you eat contains chemical energy and your body stores this energy (potential energy) until you release it when you work or play (kinetic energy). All forms of energy are stored in different ways in the energy sources we use every day. These sources are divided into two groups -- renewable (an energy source we can use over and over again) and nonrenewable (an energy source we are using up and cannot recreate in a short period of time). Renewable energy sources include solar energy, which comes from the sun and can be turned into electricity and heat. Wind, geothermal energy from inside the earth, biomass from plants and hydropower from water are also renewable energy sources. However, we get most of our energy from nonrenewable energy sources called fossil fuels -- oil, natural gas and coal. They are called fossil fuels because they were formed over millions of years by heat from the Earth's core and pressure from rock and soil on the remains, or "fossils," of dead plants and animals. All of these sources provide us the energy we need to live our busy lives. We use all these energy sources to generate the electricity we need for our homes, businesses, schools and factories. Electricity "energizes" our computers, lights, refrigerators, washing machines and air conditioners to name only a few uses. Energy is in everything. We use energy in everything we do, from making a jump shot to baking our favorite cookies to sending astronauts into space. Energy is there making sure we have the power to do it all.