Question: I need to cut an access panel on the wall for plumber to replace bathroom drain pipes. The cutting doesn't worry me and I've done all the measurements. My bathroom has tile walls so I have to cut the panel out on the wall opposite the bathroom.

But there's a problem: the access panel would overlap an outlet.

The plumber has requested a 14x14 access, but having the panel centered at the location specified would mean it covers an existing electrical outlet.

What do I do in this situation?

Answer: 
You either come up with different access area for the plumber or you move the receptacle. But even a different access area could get tricky. Let's say the receptacle is at the bottom of the area so you start the 14" vertical 4" higher up. What if the electric cable is coming down from above? Then it is hanging in the middle of the access area!

The good news is that generally speaking there is a lot of flexibility on receptacle placement, particularly vertically. If you have conduit this will be a bit more complicated, but if you have cables (as most of the US/Canada, which would match your measurement in inches) then it shouldn't be too hard:

* Cut a couple of small exploratory holes (e.g., 3" square) within the target area and near the existing receptacles.
* Look inside those holes to figure out whether the cable is coming from below or above. Or sideways. Or more than one cable from multiple directions.
* If there is only one cable (or more than one, but all from one direction) then moving the receptacle should be easy.
* If there are multiple cables then this gets a little more complicated. Cables can (with rare exceptions that are really designed for emergency repairs and not for routine movement of receptacles) only be joined inside junction boxes, and junction boxes must always be accessible (i.e., they can't be hidden behind the access panel, unless the access panel is just a simple door with no tools required to remove it.) If, for example, you have a cable from the left and a cable from the right, you might move the existing box to the left of the access area and add a new box to the right of the access area (so each cable goes for a shorter distance than it currently goes) and add a new cable between the two boxes. If you do that, put a receptacle in the new box and it will make it be useful rather than just a strange blank plate.
The plumber needs *at least* 14x14 inches - she surely won't complain if given more generous access. The reason she's asking for 14 inch width is likely an assumption that studs in the wall are spaced 16 inches on center, meaning the space between two studs is about 14.5 inches. Also because there are plastic access panels which can be installed over a 14x14 hole in lieu of repairing the drywall. Because there's an outlet in the way the access panel "repair" shortcut won't work here.

It's rather challenging to make a nice repair of drywall when there is a joint right next to an opening or an edge (like an electrical outlet box or baseboard). Cut the drywall panel larger to keep clear of the box. Make it two stud-bays wide with that outlet in the center, and tall enough that the horizontal cuts are 6 to 8 inches away from the outlet box. Keep equally far away from the baseboard if possible, or just center the lower cut between the baseboard and outlet box if they're closer than 12 inches to each other.

Make the vertical cuts centered on the wall studs. Use a magnet to locate the fasteners in the section being removed -- there's a fair chance they'll be screws, and if so, you can remove them and then the cut-out panel is likely to remain in condition good enough to be re-installed.