Disregarding physics for a second, let's imagine that at some point in the future a time travel machine is invented. It requires 3 MW of energy to use, every time, but it opens a hole in time and space to the past.
So, on May 1st, you purchase 30 MW of energy in some portable form (portable nuclear reactor - hey, it's the future, right?), and decide that on June 1st you will open a hole back to May 1st (i.e., the present) and give yourself all the energy you currently have at that point after using the machine.
If there is only a single timeline, you should end up seeing the version yourself from the future very shortly, bringing you lots of energy, which you will store and then give to the past version of yourself in a month.
How much will you get?
So, on May 1st, you purchase 30 MW of energy in some portable form (portable nuclear reactor - hey, it's the future, right?), and decide that on June 1st you will open a hole back to May 1st (i.e., the present) and give yourself all the energy you currently have at that point after using the machine.
If there is only a single timeline, you should end up seeing the version yourself from the future very shortly, bringing you lots of energy, which you will store and then give to the past version of yourself in a month.
How much will you get?