This is a subject of much debate. I will tell you what is working for us. We have a 30" GE Induction Range. We chose a 30" insert (Zephyr Vortex). It runs between 200-450 CFM and is vented with a 6" vent. I stir fry, boil water and cook things in a sauce pan with oil. It has exceeded my expectations in every way. And, I just discovered this evening that my cabinetmaker left the installation manual underneath the baffle filter so it was partially covered for the past 2 months!

If you are exhausting the air, why do you care if it has additional filtering?

I don't know about the GE model you cite, but the hoods that I have looked at only had a charcoal filter if they were to be used in recirculating mode, i.e., not vented.

As for vent size, conventional wisdom is that a smaller duct will be noisier than a larger one. If you can put in an 8", you will be better off. It will be quieter and you could upgrade to a larger cfm model in the future if your needs change. Also, induction cooktops can still generate plenty of smoke, grease, and steam!

Just because a hood can run at a maximum of 600 or 900 cfm doesn't mean you always have to run it at that speed. I say err on the side of caution and get something a little more powerful. Also, you say you have high end appliances. If so, then you should not be skimping on the hood.

Corgimum.....I've heard good reports about Zephyrs. But they don't make the style hood we need. We're looking for a chimney style wall mounted range hood. After I posted my question I found the following range hood that I really like a lot:
http://www.overstock.com/Home-Garden/KOBE-Premium-RA-092-Series-30-inch-Wall-Mount-Range-Hood/6789622/product.html That's crazy about your manual!!!

Angie DIY.....read my response above about the type of hood we're looking for.....definitely a vented one, not a recirculating. I think more recirculating fans do have charcoal filters. It just seems redundant to have both filters, and the charcoal filters would be an extra expense. So if some manufacturers make a good hood without the charcoal filter, then I'd rather get that.

I understand the difference now between the 2 size vents....thanks for the explanation.

DCJersey.....I agree....we certainly don't want to skimp on the hood, but at the same time I don't need overkill. And I certainly don't want to spend a fortune. I'd like to stay under (well under, if possible) $1,000. But my modest little kitchen needs something not too bulky or extreme looking. Honestly, the hood is proving to be the most difficult decision I've had to make in my kitchen planning....crazy!

fiddleddd, could you give the model # of the GE fan you were considering (or a link)? I am curious!

when i was researching hoods, i always heard that it is better to get a higher-powered hood even if you don't need to use all the CFMs all the time. because one benefit is that because it is more powerful, it wouldn't work as hard on the lower setting so it would be quieter than a lower cfm hood that you would be using at max power all the time.

The heat from the cook top is not as relevant as the smoke and smells from cooking. If you will be frying bacon, stir frying mean, saut�ing onion and garlic on a regular basis on your induction, you would be better served with an appropriately powerful hood that is 6in wider than the cooktop and at least as deep. You don't have to run it at max power. Just switch it on before you start cooking to get a good airflow pattern going, and you can avoid the lingering smells and smoke.

One thing to consider - do you live in a cold environment and do you have any code requirements. We have to stay under 400 and MN has a 300 CFM code or you need a make up air system. Our area just started enforcing and lots of folks got caught...

The smaller CFM fans frequently only have one fan on one side of the vent - so our 36 inch Broan Evolution (which does boost to 450) is relatively quiet, vents pretty good, but does only have a fan on one side.

Our code did allow no vent - so we didn't install until after the kitchen was done and then "decided" to add a vent - the GC had wired and had the vent in place, so Sparky and GC just had to pop in place...

It is important to turn it on in advance as LOLO says! I also agree to go 6 inches wider and wish we had done so - it is OK with induction but the space feels tight.

OT
Bacon - just learned about baking it in the oven. I ordered the grids from Lee Valley - but they haven't arrived yet - I discovered my CIA (Culinary Institute of America) grids fit either my broiler pan or 1/2 sheet pans perfectly - place the bacon on the grid and place the other grid on top and bake for about 20 minutes at 400 - worked great and a lot less mess and smell.

We just completed our hood installation last weekend, and we spent the week putting it to the test. We have a 48" wolf rangetop with a grill and griddle, and that thing puts out some serious heat and smoke. We got a 54" wide Thermador hood with a 1000 cfm remote blower, and it barely keeps up on High speed with the smoke rolling. If you plan on having a big stove, then I think you absolutely need a big hood or else you won't be able to fully use the stove like you might want. If I could do it again, I would buy the 1200cfm blower.

So far we love the setup, however I can't recommend anything made by Thermador. The range hood we purchased arrived damaged due to terrible packaging that broke during transit, the installation instructions were terrible, the hood was difficult to assemble and required modifications to fit properly, and the remote blower came with the wrong sized duct which caused us to relocate the blower and buy an extra adapter to make it fit. Their customer service basically doesn't exist, and when we did talk to a representative they made it seem like our fault. Their website still says the wrong duct size for the blower, even after we begged them to change it so no-one else has this problem. I would choose a different brand for ventilation.

The wolf stove is amazing so far.

Ok, for the original poster who says (s)he has an induction cooktop and small house, here is practical real world advice - it's friday nite, and i'm a bit ramblish (a real word?) but here it goes.

take the square footage of the room you are venting and multiply by how many feet the ceiling is. This will give you the cubic feet. For every foot of base cabinets, you have four cubic feet of area that does not need venting, so subtract out the cubic feet of base cabinets you have from your total cubic feet. See what you have left. If this is too confusing, just tell us the kitchen size and the rough length of base cabinets and we will help you.

A 400 CFM hood vents 400 cubic feet per minute. See how many minutes it will take to vent the kitchen space, then decide if it is enough for you. Corgimum above states that she is satisfied with this range and a 6" outlet. Remember that the rating of any hood is giving you the MAXIMUM that it can do, but in reality, excess length to the ductwork, bends in the ductwork, the type of cap you use, will decrease the fan's efficiency.

Once you start getting to 400-600 CFM, you will certainly need a special "make up air" duct/unit - like a2gemini says. that will start adding hundreds of dollars to your project. If you don't have a restaurant setup with a double range/grill/griddle, enormous ventilation will not be needed. Though, when at parties, many men, and some women, too, will like to flaunt the magnitude of their CFM. But, alas, size and function don't always correlate ;-)

Every time you ventilate, your air conditioner/heater will have to replace that air.

My current hood, as well as the two venting microwaves I had before it all have "filters" that trap grease before it goes into the ductwork. You don't want grease in your ductwork. The grease traps on some models are dishwasher safe, and this is a feature I recommend. Some vent hoods in the lower CFM range will filter the fumes/grease and blow the air back in the room. Those filters have charcoal to neutralize odors. The charcoal filters are not needed if you are venting outside, as Angie_DIY says.

michoumonster brings up noise, and each hood has a sound rating called "sones." sometimes it is hidden in the specs, sometimes it is even better hidden than that. the lower the number, the better. especially if you have an open layout.the quietest options have the fan up in the attic - "remote blower option" but these get pricey very quickly.

there is a nice wiki on sones:
http://en.wikipedia.org/wiki/Sone
don't buy a hood within the threshold of pain.Even if it is covered in gold leaf.

Other things that affect ventilation:
Distance from the cooktop - the vent manufacturer will have a recommended optimal distance. Width of hood - using a 36" wide over a 30" cooktop will help, but is not always possible in a small kitchen.

Our 1000 cfm unit doesn't need a make-up air duct, we just open a nearby window. The air handler for that floor of the house doesn't seem to struggle even on high. I do like to flaunt the magnitude of my CFM. If you had it, you'd flaunt it too :P

I bought both the hood and the remote blower on Ebay at a significant discount from MSRP, and installed the whole thing myself with parts from the local HVAC supply house. You don't have to spend a fortune to get what you want.

If it helps, we have the Kobe chimney hood (RA-094, 280 to 760 CFM) in a small house with a 6" vent. We contemplated going up to an 8" vent in the attic for noise reasons but didn't for unrelated reasons (roofer got a break in his schedule, had a 6" cap on hand that matched our roof--done!) Can easily change it in the future if need be since it's vented through an accessible attic and, aside from the roof cap, only took us an afternoon and a few ducts from Home Depot. No makeup air requirements where we live, and we have an old house that isn't (remotely!) airtight so it hasn't been an issue.

We're very pleased with the Kobe a year and a half in. We also don't have a high BTU stove, but for a consumer stove, it's more than adequate. Only time it doesn't vent quite enough is if I'm boiling a lot of water at once (canning, etc.)--then the windows will steam up before it catches up. But it's stellar for stir frying and other oil tasks. Ours has baffle filters that go in the dishwasher and come out like new, which I love. You can definitely hear it when it's on the two highest settings in other parts of the house (1250 sf all on one level--kitchen is 230 sf) but on the lower two it's not an issue. That seems reasonable to us. Only thing we dislike is the strange setup for changing the speeds--you have to cycle through all four--but we've gotten used to it. Would absolutely buy it again! HTH.

Sorry it's taken me awhile to get back here. Thanks for all your responses....some very helpful info here.

Angie_DIY......Here is a link to the GE hood we're considering. After reading the manual I realize that the charcoal filter is only needed if you're using it as a recirculating fan. We won't be. There is also a grease filter that is washable.
http://products.geappliances.com/ApplProducts/Dispatcher?REQUEST=SpecPage&Sku=PV970NSS

michoumonster.......that makes sense, and I certainly would not be using the fan on high all of the time. But some other comments have mentioned that code often has a limit on how many CFM's are allowed. We're moving to a small little community where they are sticklers about code (we've had fits with them on several other issues), so we'd better check to see what is allowed first.

GWlolo.....Yes, I've read that the hood should be slightly wider than the cooktop. Ours won't be unfortunately. We have a 30" cooktop and a 30" hood, but I guess the range hood will extend beyond the actual burner area, so I think we'll be okay. I have to confess that until recently I didn't know that range hoods removed odors from cooking. For years I had a Thermador down-draft cooktop, and the fan was so loud that it honestly sounded like a jet engine taking off, so I didn't use it except on rare occasions. It's nice to know that in my new kitchen I'll be able to get rid of smells like brussels sprouts!

A2gemini.....I agree...that's the only way I'll make bacon anymore, and I just learned this method about a year ago. BTW, we do live in a cold climate, and we do have building codes to contend with. But I didn't realize the hood CFMs would have to be considered. See above where I talk about this. I guess I have some checking to do.

WileyBob.....I agree about Thermador....I never liked my down-draft, and I had it for about 20 years. I finally replaced it with a GE Monogram cooktop. I like it much better, but I still rarely use the down-draft. I'm looking forward to having a normal hood above the cooktop. I won't need anything as powerful as you need with your Wolf though. I've heard great things about the Wolf cooktops.

Detroit burb.....I wish I had read your information before I started my research on range hoods. Good info there! The thing I've had the most trouble with is finding a 'not-too-high' CFM rated range hood with a low sone rating. We need something not too bulky looking, yet we still want a decent performance. So I think we're just going to go with the GE curved profile style in the link I've posted above. It's noisier than I wanted (7 sones on high), but I'm sure we won't have it on high for long periods of time. My husband and I did your calculations on CFM vs. room size, and I think we'll be okay with that one. Thanks for your help!

artemis 78.....I also like the Kobe's, and we were considering going to Cincinnati to look at them (they don't sell them where we live), but I fear the building inspector (they really do inspect here) would think the CFM rating is too high. But I'll check on this.....glad to know you like yours. We're moving to a modest little home (we plan to spend most of the year in our RV), and I'm sure we already have the best kitchen in the neighborhood. We plan to stay in the house forever, so we're making it as nice as we can within reason for the type of house it is.

Thanks again, everyone!

After reading the manual I realize that the charcoal filter is only needed if you're using it as a recirculating fan.

Ahh, I thought so. Great news.