Wow - am having exactly the same problem.....My 35 year old Thermador measures 25.5" wide x 51" tall on the outside. I believe the hole is 24" wide - and the inside wall-to-wall cabinet measurement is 25.5" wide. That's too small for a "27-inch" wall oven (the cutout hole needs to be about 25-25.5")- and I believe it is recommended to have some air space around the body of the oven (although none of the manufacturers say this in their documentation). A "24-inch" wall oven needs about a 22.5" or so cutout - as mine is 24" that's too big. Would be a big job, and very noticeable to try to put a larger piece of wood on the face of the cabinets - would be impossible to remove the old and put in a new one and stain it to match.

I've had no luck with any appliance dealers helping me find one that will fit the hole, at least width wise! I'll let you know if I find something...

Check the online installation instructions for the 27" models you're interested in, which will indicate the exact interior dimensions of the cabinet required. Generally, a 27" oven will fit into a 26" opening, as the 27" measurement includes the flange that overlaps around the front edge.

When we were replacing our wall oven, I also struggled with this. Outside measurements don't tell you what the cutout measurements are, you have to pull the oven slightly out in order to get these numbers.

We got a 27" Elux wall oven and needed about 1/4" extra width which we were able to get by shaving 1/8" off the cabinet opening on each side. No-one sees the opening once the new oven is installed. Behind the cutout in our cabinets, there is extra width so there is air space, although this is not specified in the installation instructions.

In order to accomodate the extra height, we had to move the shelf above the oven opening. A good cabinet person should be able to take care of all of this.

Cheryl

Thanks for the info...I would love to use a 27" but my concern is that generally they are about 25.5" on the inside, which is the exact measurement of the inside width of my cabinets - that means if it can be shoved in there (after widening the cabinet opening all the way to the edge of the side pieces), there will be NO air space - the oven will be right up against the cabinet walls - seems like a really bad idea - does anyone know if the outside walls of the oven are warm or hot to the touch while in operation? Thanks!

Again, check the installation details for a model you're interested in: they will indicate the minimum opening size. If they say the size is OK, then it's OK: they've determined the safety of the fit. If it needs a tiny air space, their installation minimum opening size will take this into account.
They manufacture the product: they know what's required. After all, if anything goes wrong, they're the people you'll be sueing.

What Sara says is true. If the unit is designed for 0 clearance, then it will have been tested this way in order to get its UL approval.

However, it is always a good idea to leave a little room on each side to allow for wiggle when inserting and removing.

Same problem here, a 1986 Thermador that has a 24-3/8" opening. Nothing out there that I could find, so I'm switching to a Range...