Calculating photosynthetic efficiency?

Question

While calculating photosynthetic efficiency, do we take into account the Gross Primary Production or the Net Primary Production ?

Answer 1

Think that would depend on what you are studying.

If just interested in the efficiency of extracting energy from sunlight, would go with Gross.

If interested in the plant's ability to turn sunlight into useful products (sugar) would go with net. There are side reactions that need to be cleaned up that reduces the plant's overall efficiency.