mivey:
Our discussion is not about whether the OP requires MV supply or not but about the industrial practice i.e the statement
To conclude:
80% loading of transformer is an industrial practice. This may be adopted in the OP's case.
is applicable or not.
Really? So we come full circle?
The load calculations include safety margins for things like power factor estimates, parasitic loads, etc. This is the reason Laszlo said he would not load a transformer to 100% because there was not room for safety margins given the sketchy information from the OP. That went completely over your head.
As part of our load estimate, we often include known near-term growth in the load calculations as well. We also include things like room for load swapping in emergency conditions. After these base loads are estimated, it is generally acceptable to include a factor for unknown growth if it is reasonable to do so and this is where we get the 80% practice. This number may be higher or lower based on experience with the particular load type.
You started out stating the OP should use this industrial practice of 80% loading. That practice is to allow room for growth above the current load. Well guess what?: A static load needs no allowance for growth. When called on that you came up with the silly notion that the practice was not for growth but for other things like losses. On the contrary, losses are included as part of the base load calculations.
We went down the whole road of demonstrating why this loss goofiness was a premise based on ignorance of the topic. We would not reach a 20% loss under reasonable conditions. Even if we did with a goofy scenario, this size load would be calculated as part of the base load since it is not something you would ignore and account for in the slop. A parasitic load this big would not be left up to some wild swing using some percentage grabbed out of the air.
We are now back to the beginning where you propose that the OP buy more transformer than they will ever use. What possible reason will you give now?