Your contractor is basically correct - he's referring to the GE PEM31 - (I have the previous model JEM31). The trim kit is needed to enable the MW to vent out the front. Without the trim kit, you'd have to leave enough room around the MW for venting.

The one other model that can be built into an upper cabinet is the Sharp R-1214. I don't think it uses a trim kit but it needs to vent out the bottom.

Thanks a lot for your Reply. Will shop around.

I'm starting a renovation and have been looking around for options. I can't vouch for the Frigidaire microwaves (other than I am leaning towards Frigidaire for everything but my cooktop), but they seem to be another option for you.

Frigidaire FGMO205KF - http://www.appliancesconnection.com/i132027-frigidaire-fgmo205kf.html#tabs

30" or 27" Trim Kit seem to be available for another $150.

Looks like the combined prices are about the same. One appliance guy I've spoken to thinks GE Microwaves are solid, but the Frigidaire is a solid performer, too. He advised to go with what matched better. If it's really a toss up, he says to stick with the GE.

that Frigidaire MW is over 19" deep - can't be built into an upper cabinet - only into a full depth oven cabinet

Built in appliances with relatively short lives like microwaves are relatively expensive over time. My mother has a "hole" in her kitchen with a cheap microwave sitting on foam blocks because the cost of replacement with the trim kit was excessive.

Today, I would get a free standing stove and counter top microwave to avoid this issue in the future. While not as trendy, when I need to replace them in my retirement with less income, it will be financially possible and won't leave me with a "hole" in my kitchen.

I put our countertop microwave into the upper MW cabinet -- it's just a normal 24" wide cabinet with shorter doors so that the bottom shelf is exposed. It comes with a slightly deeper shelf insert so that a MW that is deeper than the cabinet will fit. The MW doesn't look built-in because there is no trim kit. Many countertop microwaves will fit with the shelf insert; the depth is the limiting factor otherwise. Anyway, my years-old midsized (1100 W) GE microwave fits nicely in there and I don't expect any problems finding another one to fit when it finally dies. In fact I have already found a nicer-looking (meaning newer-looking) Sharp that's the same dimensions and power; just haven't bought it because we don't actually need it. If you go this route using a countertop model, it's probably a good idea to check clearance requirements behind the microwave. My old GE doesn't have any clearances specified (I double checked) and so far so good.

A lot of people put their microwave into a finished hole or sleeve a/k/a "cubby" in the new cabinets, with a plug on the back wall for a countertop model. It is done on a regular basis around here. Go to houzz.com, select Kitchens, and in the search feature type in "microwave" and you'll see some photos.

There is a frigidaire model #FFCM0934LS, 19" x 13 3/8 deep x 11 3/8 high, 900 watts power. This would work well on a shelf and its on my list to check out.

The Sharp 1214 is an over-the-counter microwave oven. It "wants" to mount to a cabinet that is shorter than others (top-to-bottom) so that the bottom of the microwave is level with the other cabinets. Sharp has some literature showing mounting approaches. It vents to the bottom, as noted, and has to have an air gap at the back. It has lights on the bottom for counter illumination.

I have one. I deliberately reinforced the wall for it when rebuilding the kitchen (the microwave is fairly heavy), but this may not be required. The back attaches to a plate mounted to the wall; the front is held to the cabinet by two screws from the top. These screws can strip if the front weight of the unit is being pulled up with them. The unit should be propped into place when tightening the screws. (A cabinet jack works well, but a stack of books would also work.)

The unit has worked uneventfully since early 2008. One trim piece has fallen off, but it just awaits my taking the time to clean its sticky side and reattach it with some automotive trim tape.

The only design defect I have noticed is insufficient back-up storage power for the clock, which loses track of time after mere seconds without power. (My Wolf ovens, on the other hand, do not have this problem.)

kas