Considering I am looking at having to install complicated ducting to get a hood vented to the outside..and am willing to jump through all sorts of hoops to do it...and you already have the venting installed, I would most definately put in a real hood and find someplace else for the microwave. From what I understand, the changeout isn't too hard. The microwave is held in by a couple of screws.

Do a search on OTR microwaves and you will find out quickly the consensus is that they don't really work too well.

My MW was recirculating. I removed the MW and ran ducting to the outside to add a vented range hood.

I looked at Vent A Hood and really liked them but found a great deal on a KA range hood. I have KA appliances so it matches.

I absolutely love having the range hood vent to the outside.

The MW was donated to Habitat and I bought a new MW that fits in my island.

I do not do a lot of major cooking so if you cook a lot, you may want a more powerful vent hood.

If you are lucky enough to have no studs behind the vent rectangle, AND not moving the cooktop's location, it's very doable.

You already have power there obviously, perhaps an outlet, but the range hood needs to be hardwired most likely. Cabinetry needs to be modified to mount the hood and cutout for the duct. unlike OTR microwave that mounts on the wall.

You may need the help of a pro to bend the rectangular ducting for you, depends on the route it needs to make.

A "fairly easy" to install one would be a tiny one that is easy to lift up.

Mine took a little work because I replaced everything including the vent outside the house, and I had to move it a few inches to centered it to the new cabinet.

Thanks for the responses. It seems like it's going to be a lot more involved and expensive to do this than to just get another OTR microwave because it's going to require electrical work, carpentry, maybe drywall repair, buying a vent hood AND a microwave -- and we don't have anyplace to install one elsewhere, or even a good place to put one on the counter. We have a smallish kitchen with no island.

I think it's back to trying to pick out an OTR model for me.

Harrietthehomeowner, I replaced my BRAND NEW OTR MW with a hood about 3 months after I installed the OTR MW in my brand new kitchen. I really detested that MW. I think you said you already have the ductwork, right? Then I don't know why you believe you'll need electrical work (the MW needs electricity, so if you already have the electricity for the MW you don't need more electrical work), carpentry (why?) and drywall repair (why?).

The biggest expense in my replacement was the hood itself. Countertop MW's these days are pretty low-cost. I bought a large countertop MW, with actually bigger interior space than my OTR MW, with all the bells and whistles like sensor cook, several defrost modes, etc., except convection (I didn't want convection). That Sharp countertop MW cost me about $120. I put my MW on a shelf in my pantry. The other expense was tiling. I had a backsplash up to where the OTR MW was. But the hood is higher, and so I needed to bring my tile guy back to fill in that space, I think it was 3-4 rows, 30" width, so wasn't that big of a deal. Luckily, I had plenty of extra tile from when he did the backsplash in the first place. I sold my OTR MW on Craig's List, which wasn't too hard since it was practically new, although I could have also donated it to Habitat for Humanity, but it didn't occur to me at the time.

Here's why I detested my OTR MW:
- OTR MW's just have a couple of little mesh screens for exhaust, very inadequate.
- capture area is a joke. Since the MW only hangs over the back burners, it can't capture anything coming from the front burners, and even the back burners are inadequately captured, given the little mesh screens I already mentioned.
- my OTR specified 300 cfms, but hardly exhausted anything.
- little mesh screens got clogged very quickly, since they are so small, making the exhaust even less effective than it already was.
- as a short person, I found it awkward trying to peer up into the MW to check on things cooking.
- OTR MW is really noisy. My replacement hood isn't dead silent either, and in fact I believe no hood is unless it has a remote or in-line fan. But that OTR MW exhaust fan was like having a 747 in my kitchen.

I do understand that in a small kitchen, sometimes the only spot for a MW is OTR. But barring that, I wouldn't recommend one.