500 Factor

The 1000 factor is a factor calculated theoretically as the limit of possible increase of energy by humans, without suffering from ecocide.

This number is a number that allows for solar energy to power all natural processes such as weather phenomena, natural life, along with human-made processes such as the conversion of solar energy into useful power for industrial processes, indoor heating/cooling, transportation, etc.

Plants are the largest users of solar energy. Plants use only 1-2% of the incoming solar spectrum [1], and the earth's coverage with plants is about 30% [2]. Since only plants can use solar energy, and animals build ecosystems upon plant energy - the plant energy is the primary energy important to overall solar energy usage. Ie, animals do not use solar energy, outside of the heat - a component of weather. Bottom line - the amount of total energy required to sustain the ecosphere is under 1% of the total incoming radiation.

.

Source: [3]]