What does the energy in an energy pyramid represent?
Each layer in the energy pyramid represents the stored energy in biomass in that layer. This energy is obtained from the previous layer. Because every layer uses a certain amount of energy needed for survival (combustion of sugars and fats through respiratory processes) obtained from the previous layer, each subsequent level is smaller than the previous one. Also, the autotrophs in the photosynthetic layer use up (solar) energy for living. The higher up you get, the more energy is cumulatively taken away to sustain life and growth of the previous layers. Therefore, it's a pyramid shape. 


Energy pyramid. Source: Biocab