About 99% of the energy output of the sun comes from the various p-p chains, with the other 1% coming from the CNO cycle.According to one model of the sun, 83.3 percent of the 4He produced by the various p-p branches is produced via branch I while p-p II produces 16.68 percent and p-p III 0.02 percent.The difference is apparently due to slightly different assumptions about the composition and metallicity of the sun.