Well even with induction your appliance should have some specs available. But if not, I'd do a minimum of 900 myself. I don't like any smells to leave the kitchen without permission. Ventahood's 900 is equivilent to a 1200 aprox so it can handle just about anything. The highest priority is actually coverage of the hood. You want it to cover the front burners and overlap the sides a few inches Ie 42" for a 36" cooktop at least. I bumped mine out since my range sits out, but that isn't an issue it sounds like.

Even with induction, you have grease and smells that come from general everyday cooking. A good hood deals with this as well as the smoke from a fish fry :) Sure it's a bit about sucking up wasted heat, but really, that's not the priority...cleaning the air is.

I don't think the fact that it's induction really matters.

You don't run the vent to remove excess heat or combustion products from the gas flame itself. You vent to remove smoke, smells and oils released by the cooking food, and that depends on the temperature of your pan and the quantity of food being cooked, not the heat source.

If anything, seems to me your chances of setting off the fire alarms with the more powerful induction burners would argue in favor of oversizing the vent vs. a gas or radiant electric range.

Using the rules of thumb you can find all over the internet, you will need anywhere from 100 to 150 to 250 CFM. My saying this is not a recommendation, it's just information. I could easily "recommend' to a stranger to double all these numbers.

If this is to be a restaurant quality setup, or a commercial range, double or triple that all over again. Caveats apply. You need makeup air. What climate are you in?

Miele, a high-end company not known for undersizing anything, says their 400 CFM power pack (operating on a 6" round duct) will be fine for a regular wealthy person's average kitchen.

Garden Web has a number of keeners who kiddingly say they are "kitchen obsessed" and who prod each other onto bigger and better products all the time.

In Garden Web's Appliances forum or Kitchens forum you will find 90% of the people who respond will tell you to have More, and they will say anything less than what they recommend is not good. These people are quite vocal and think nothing of speaking up again and again. Occasionally someone else (not the most vocal) opens a thread that contradicts all the vocal people, and three or four lurkers or non-vocal people all chime in and say "yes this is right yes this makes sense" and then the thread dies out and disappears within a day as it gets sent off to page two and beyond into past history. Then the vocal people all just start up all over again saying You Need More.

This is very true of CFM and vent hoods.

Personally, I like having More of anything, except when it's just craziness to go that far. I will not be installing hundreds and hundreds of CFM.

HTH
David

Here is a link that might be useful: Right Size blower, over induction cooktop

If the hood was 1" above the cooktop, 100CFM would even be overkill, but as we know, that will never be the case. The wider the hood is (they range from 24" to infinity) the more CFM you will need, because you are also exhausting all the room air below and between the source of the smell and the fan itself. The higher the hood is above the cooktop, the more CFM is required to be effective.
I'm an impoverished carpenter, so the "wealthy" characterization is WTF? I have a 36" range with grill, a 42" hood with 1000CFM and 10" ducting, and that combo barely keeps up.
Casey

Good point about height being the Real Big Factor. Focus suction on the cooktop, get closer to the source. -- Makes me want to build my vent openings into the wall behind the cooktop. Then the suction will be closer. Ten or twelve inches away. I'm building my own. I've been studying where to position a tempered glass "sneeze guard" slider device so I'd have a vent hood lower than ever before. It would slide back when not in use, under the floor of the upper cabinet over the cooktop.

In a Nutone webinar I saw last fall, they said: "This above all: A.) avoid cross breezes and B.) Place it as close as possible."
The third thing was to have some height for smoke to collect inside an umbrella shape. (i.e. not to have the bottom of the vent hood be a flat plane where the filter was at the same level as the bottom edge).

Casey, you didn't say how high above the grill your 1000 cfm beast is. From the counter to the filter. I'm glad you agree that 100CFM could be overkill when focused on the source. I won't characterize you as $$ or not, but you sure have a lot more power than millions who have no vent, or a recirculating, or a weak propellor blade blower that cost peanuts only, or...

-dr

I've posted this before, but:

I have a 48" bluestar with grill. Vent is mounted 37" above [Independent rated at 1400cfm, two 90 degree bends].

When I grill steak and have the vent at low or medium speed, I can see smoke escaping the vent enclosure, and a haze of smoke shows in the can lights throughout the kitchen.

At high, [nominally 1400 cfm] it all goes out the vent.

Consider it overkill if you like, but I'm very glad for every one of my cubic feet.

"Makes me want to build my vent openings into the wall behind the cooktop."

Now you have a distance problem with the front burners, just like the various pop ups.

The hot smoke is also trying to rise, so if you pull from to low behind the top (like the pop ups) it ends up needing a huge draw (again).

I have a 30 inch viking hood (not the remote fan model I left at the previous house) over a 30 inch viking dual fuel and can easily fill the room with smoke from a cast iron griddle or anything that smokes on the front burners.

You can see how much grease/oil gets trapped on the filters (and drips into the lower channel).

If you get a decent size unit with a variable speed fan you can always adjust the speed and flow (and the noise) down to match the task at hand.

Doing heavy smoke tasks on the rear burners also helps.