"essential factor in" is correct and usable in written English.
You can use it to describe something that is critical to a particular process or event. For example, "Time management is an essential factor in being successful."
Machiavelli said that "surprise is the essential factor in victory".
Deep cuts in such spending were an essential factor in the economic downturn.
Her physical presence was an essential factor in conveying the music.
"Folate is an essential factor in the synthesis and repair of DNA".
The essential factor in a framed building is the frame's strength.
And they seem to believe that "economic power is the most important and most essential factor in comprehensive national power," as the latest Pentagon assessment of China's military described the Chinese credo.
Mr. Zenkel said the essential factor in luring office workers was to give them the aura of freedom; there was no pretense that they are in an office, even though they might be working intensely for hours.
If my years on the frontline preventing suicide and tic-tacking 35,000km plus across the remote north west, have taught me anything, it is that self-determination is an essential factor in the fight against suicide.
Perhaps the essential factor in celebrating the life of a physician, especially this physician, Dr. Arthur Gray, is to observe that his patients knew that he cared about them, and that so many of them thrived under his care.
The essential factor in early treatment is to seal off the tear in the retina if there is danger of detachment.
Moreover, target-specificity is also an essential factor in the novel sensor development.
