In this article it is claimed that photosynthesis efficiency could be up to 60%.

The closest process to artificial photosynthesis humans have today is photovoltaic technology, where a solar cell converts the sun’s energy into electricity. That process is famously inefficient, able to capture only about 20% of the sun’s energy. Photosynthesis, on the other hand, is radically more efficient; it is capable of storing 60% of the sun’s energy as chemical energy in associated biomolecules.

The claim has been repeated by many news outlets around the world, it seems they all took the claim at face value without any verification.

However on Wikipedia it is claimed that the actual efficiency is much lower.

Plants usually convert light into chemical energy with a photosynthetic efficiency of 3–6%

Furthermore another Wikipedia article linked in the first comment to this question notes that the even the theoretical maximum efficiency is way less than the claimed value.

For actual sunlight, where only 45% of the light is in the photosynthetically active wavelength range, the theoretical maximum efficiency of solar energy conversion is approximately 11%.

Why there is such a difference? What is the actual efficiency of Photosynthesis?

  • 6
    The difference is in exactly what kind of efficiency is being reported. If you consider the ratio of the energy involved in fixing CO2 by the plant to the total solar irradicance, you get the smaller number. If you take the microsopic efficiency of the chemical processes directly involved (ie. photon+chlorophil+CO2+H20 => C6H1206) then you get the higher number. This is what the first part of the wiki article is saying.
    – Dave
    Jun 21, 2021 at 18:54
  • 6
    So to some extent, the problem is in specifying what "actual efficiency" refers to.
    – Dave
    Jun 21, 2021 at 18:54
  • 4
    @Dave that looks like an answer Jun 21, 2021 at 19:10
  • 1
    You may have better luck with this on the biology stack, one problem you will run into is it varies by quite a bit depending the plant and form of photosynthesis, all plants don't use the same process. You will also run into the issue of defining efficiency. this question may help you get started biology.stackexchange.com/questions/97772/…
    – John
    Jul 11, 2021 at 20:07

1 Answer 1


The difference is in exactly what kind of efficiency is being reported. If you consider the ratio of solar energy that falls on a leaf to the energy in the resulting biomass, you'll get a lower number. If you consider the ratio of the energy of the photons interacting with chlorophyll to the energy of the resulting NADPH you'll get a higher number.

I haven't seen efficiencies as high as 60% reported for photosynthesis, but have seen indications of >50% molecular-level efficiencies for respiration, which is, in many respects, just photosynthesis run backward.

  • 1
    The linked article and all the copy articles published around the world make a comparison between photovoltaic efficiency which is calculated according to the first criterion you mention and photosynthesic efficiency calculated according to the second criterion. Am I right?
    – FluidCode
    Jun 26, 2021 at 10:45

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