What happens to the amount of energy available each successive trophic level in a food chain?

As you move up each successive trophic level in a food chain, the amount of energy available decreases roughly by 90%.

This loss occurs because some energy is lost as heat during the transfer from one trophic level to the next. Additionally, not all of the energy in food is assimilated by the organism that eats it. Some of the energy is lost as waste products and some is used for metabolic processes. This phenomenon is known as the "10% rule" or "trophic level efficiency".