There are much better options for kitchen ventilation than an OTR microwave. They barely function and if they are on recirculate, they are virtually worthless (this is true of other fans as well if on recirculate).

What you need is dependent upon what type of cooking surface/unit one has. If it is a gas range, IMO, the cfm of the ventilation unit needs to be a minimum of 400 cfm (or larger depending upon range size). If over an electric cooktop, then a 400 cfm would be nice or something slightly smaller would work.

Have you checked out down-draft exhausts?

The previous posters have all made very good comments. One additional comment is that most OTRs must be set 18"-24" above the cooking surface in order no conform to the manufacturers warranty. Makes if very hard to see into the posts on the back of the range. Also, read the manufacturer's specifications on the cooktop/range to verify what distance they require a hood be from the cooking surface so that you do not void your warranty on the cooktop/range.

I had an OTR microwave and I despised it. I am short and while I could reach it, it was not convenient for me.

There was also plenty of steam that would circle up and hit the cabinets above the microwave because the fan was too weak.

If you couldn't tell from this, I wouldn't recommend one to most anyone, unless you use the microwave more than the stove and stand over 5'3". :-)

just bought a house that has an mw over a gas range. I was like, where's the vent? No vent, I was told, only a filter which you have to change. But I was told I "if I cooked a lot" I had the option to take it out and put a hood in vented to the roof. Hmm. . . wonder how much that would cost!

cloudlb, my condolences. Expect to pay $300-$400 for the roof penetration, ducting and roof cap. You can probably install the hood yourself, not too challenging.

yeah. I'll put it on the list. Meanwhile, I'll enjoy having a smaller mw that doesn't take up counter space. And change that filter regularly!

@mbme and @cloudlb:

Microwave range hoods don't work. Period. They're too undersized and their filters are too ineffective to make them anything other than an afterthought. Downdrafts are slightly better, but still do not measure up to a full-size, ducted range hood.

Adding an outside duct and installing a full-size overhead range hood might be expensive, but it makes a lot of sense in the long term. Besides the immediate benefit of removing the smoke & grease from cooking, a range hood that's ducted to the outside offers a few other bonuses.

Check out this article we wrote explaining the benefits of range hoods:

http://www.futurofuturo.com/rangehood-FAQ-10-reasons-to-have-a-range-hood.php

(copy the link & paste it into your browser address bar if it's not clickable).

...

"A Kitchen That Works LLC" is right, you can save some $$ by installing the actual hood yourself. The ducting and electrical supply will have to be done by a professional, by to install a wall-mount hood, you don't need much more than 2 people, a power drill, a level, and a screwdriver.

I'm altitude confused. I think if you can find a otr mircrowave with 400+ cfm then that might suffice. The rule of thumb is 100 cfm for every 10,000 btu. Add up all the burner btu's and divide that by 100 and you get the cfm rating for York vent. This of course assuming that you will vent external.

I have a Bosch gas range 3 years old. I researched microwaves extensively until I found a ge otr micro. It had the highest cfm out of all the other otr micros @ 400 cfm. No problems with gas fumes either. And the fan will suck a piece of copy paper right out of my hand! Just make sure the micro is at the correct height per your local codes. Sure I would have rather had a nice futuristic vent hood, but when the house was built in 2015 the builder side vented the micro like the rest of the other houses in the subdivision and I didn't want to spend the extra money to punch a hole through the roof. Model # JVM7195SKSS and a few other models have the 400 cfm fans as well.