I have such a problem: it seems like I did everything right, but the value of “_energy” is not taken away every second as I wanted it, but every frame. Thanks in advance to everyone who helped =)
Yoho,
the problem you have is that you start a Coroutine each Frame. Do it in Start instead of Update and you are good to go.
For a more in depth explanation check out this question here where another user had the exact same issue.