Energy in ecosystems flows from producers (photosynthetic organisms) to consumers (herbivores and carnivores). Ecological pyramids of energy usually depict the amount of living material (or its energetic equivalent) that is present in different trophic levels. In this diagram, energy is depicted in kilocalories.
Primary producers convert only about 1% of the energy in available sunlight. The average amount of energy that is available to the next trophic level is about 10%. Because so much energy is utilized in building and maintaining organisms, food chains (series of feeding relationships) are usually limited to just three or four steps. Pyramids of energy can not be inverted. 
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