When the machine is out of power it says the recipe is not found. Yes, I'm aware the power requirement is part of the recipe but can this be separated out to let the user know that's why it's not working. Since there is not power indicator anywhere, this would be a really nice addition.

Consider having some amount of recipes for a built machine.

Now the recipe check runs over all of them, essentially finding no recipe that "matches".
Recipe 1 needs 2 items as input and outputs "something", doesn't need power at all.
Recipe 2 needs 1 item and power as input and outputs "something". needs power obviously.

What to display? "Not enough energy"? "Missing items"?

Sounds like bad recipe design for the same machine to me, if one requires power and the other doesn't for the same machine, so maybe an irrelevant concern there.

Aggreed-on solution: If all recipes for a given machine have a energy-requirement, it'll print the power-warning if that's preventing a recipe. Otherwise, it'll not print that and behaves like it does now. (Behavior extrapolated from the "Either all recipes need power, or none do"-statement)