In most energy transfers there is no loss of energy at all. Historic energy conversion sequences biomass heat esp. Some of that energy is stored as fat some is lost through wastes urine and feces. There are two ways in which we can reduce energy consumption. This means that when energy is converted to a different form some of the input energy is turned into a highly disordered form of energy like heat.
How everything happens energy makes everything happen and every time something happens there is an energy change. Cooking solar heat dry clothes dry food solar is still main light source no need for conversion. Functionally turning all of the input energy into the output energy is nigh impossible unless one is deliberately turning energy into heat like in a heater. In physics energy is a quantity that provides the capacity to perform work think of lifting or warming an object.
For example a roller coaster sitting at the top of a hill is said to have potential energy. An organism acquires energy from the food it eats. Energy transformation also termed energy conversion is the process of changing energy from one of its forms into another. This reduces energy transfer by conduction.
Energy transformation can also be explained in terms of potential energy the stored energy of a system which can be converted into kinetic energy the energy of movement. If one unrealistically assumes that there is no friction or other losses. Different forms of energy can be transferred from one form to another. The concentration of thermal energy is the same on both sides so there is no more energy flow.
There is air or an even better insulator such as argon gas between the two panes of glass. When energy is transformed from one form to another or moved from one place to another or from one system to another there is some energy loss. But most escapes as heat which is produced when energy is transferred from one form to another. This reduces energy transfer by conduction.