There's no way to even give an aproximatly accurate answer to this question, since it depends on what you do while you're playing and your xp boosts (scrolls/eso+7drinks).
I suggest you figure out how much xp it takes in total, how much xp you gain in one session/hour of your usual activities or grind and do the math then.
The XP required for Champion Point gain is based on the following formula:
(((x / (cap ^ 0.995)) + 0.085) * 400000) if x ≤ cap
(((x / (cap ^ 0.995)) + 0.085) * 400000 * 1.5) if x > cap
x is your current number of Champion Points.
The current cap is 810, and you are unable to spend any points that you have earned above this cap. This means you are able to spend 270 points in each of the three constellations.
Source: https://en.uesp.net/wiki/Online:Champion
Also look here: https://forums.elderscrollsonline.com/en/discussion/222827/xp-needed-per-champion-point-in-eso-2-2-0
I don't grind past daily enlightenment, Would it be doable to get to 810 if I did though?