Do you have to pay the Energy cost of a Power in order to Repeat it?

Do you have to pay the Energy cost of a Power in order to Repeat it?

Not inherently, but most effects that let you Repeat a Power explicitly require you to pay its cost. If an Energy cost is not explicitly required by the Repeat-granting effect (e.g., the "Gift of Strength" Innate Power of Vital Strength of the Earth), then don't pay any Energy.
That being said, if a Power has an explicit "Cost to Use" in its text box, you do still need to pay that cost whether or not the Repeat-granting effect says so.