I'm replacing a JennAir. The opening is 29" x 21.5". I've been looking at Bosch Benchmark and 800 series, both ⅛" short in width and much shorter in depth. The GE is half an inch short in width. Thermador is a quarter inch short.

I am certainly no tech expert on fitting cooktops, but I just had to replace mine and I suspect my observations may be useful. The cutout measurements are there to allow the bottom box of the device to fit thru the granite. All cooktops must have a lip to hold the unit. One quarter inch extra is essentially trivial and in fact would likely be expected to allow easy fitting. The question really is whether a whole inch would be excessive even if the lip is bigger than that and I would think the lip is even bigger. In any case, the front and sides all hold the cooktop, and the back would as well, except for the pop up downdraft.

When I replaced mine, I had to increase the depth because my new cooktop box was one quarter inch deeper requiring the pop up vent to be moved back. I found that I could cut the granite myself. It wasn't as difficult as I originally expected. I happened to have a little tile/stone/granite cutting saw that looks like a baby skill saw and a grinder. One needs both and some plastic to hang from your lights or something to catch flying crud from the grinding dust/mud. I used wet cutting by attaching small tubing from my faucet to the saw. This required some plastic below funneling into a bucket to catch some of that water (slow flow)! Actually, it was so little that a towel would have sufficed.

Thanks for that information. I wasn't sure how difficult cutting the granite would be. Is the cutout for your downdraft the same width as the stove cutout?

Loonie: We installed the Bosch 30" induction cooktop and downdraft into our island earlier this year -- just love it! I'm hoping these pics help -- I randomly took photos during our reno, and they oftentimes come in so handy!

First, here's everything installed -- vent hood towards the bottom (the stainless steel strip):

And here's the same view/orientation of the cutout:

And here's a shot of the cooktop installed without the vent hood in (I hope the site flips my pic the right way):

You can see how much in excess the cooktop and vent hood sit beyond the cutout. I hope this helps. I do recall that one of the dimensions of the cutout in the Bosch manual is incorrect. Gosh, it's been so long, I'm afraid I don't recall off the top of my head: but when you stare at the diagram, and add cooktop cutout (depth) to vent hood cutout, the numbers don't add up.

HTH!

Thanks! The pics help a lot. Do you like the bridged burners?

I do! What sold us on this specific model was the hob configuration. I get that downdraft ventilation isn't optimal, but we love (yes, love -- there, I said it, GW!) our island cooktop. Most of our boiling and sauteeing is done on the back, larger burner, right next to the vent hood. The fan's pretty loud (subjective, yes), but it doesn't bother me. Cranked up to the highest level 3, it really pulls! We have far less cooking aromas in the house than we used to (had used a downdraft Whirlpool for 25+ years).

Here ya go -- one more: hood in the raised position.

The vent hood gets installed first, and it has a small front lip that the cooktop kinda slides into/rests on top of. The cooktop comes w/ or w/o the SS front and back trim. Our sales told us that Bosch will not allow their dealers to sell the cooktop + vent hood combo w/o the SS trim model cooktop (i.e., glass only). He seemed to think the glass portion that rests on the vent hood lip might be more prone to breaking/chipping. No matter to us, as we were going to get the SS trim version anyway.

Glad to hear you are pleased with the vent. I wasn't sure if I wanted SS or glass until reading this. I like the look of all glass, but we're replacing the all glass JennAir because of a chipped edge so the SS trim is probably the best way to go. I like the looks of yours, too!

If the space is a 1/4 too wide you can always epoxy a 1/4 in thick piece of wood to one side or instead glue 2, 1/8 inch boards to each side of the granite. The cooktop will cover the boards and your dimensions will be correct.

Javiwa's pics are very helpful. You can see that the vent cutout is in fact a different width. My vent is even less wide than javiwa's. That width accuracy is more important than the cooktop because the only thing really holding the vent is those ~2" sides of the vent. The precision also keeps the vent from leaning forward (mine didn't have an extra trim like javiwa's.) All these corners need to be cut square and that is why a grinder is needed to essentially carve the circular shaped 'skill saw' cuts into square edges. I believe that my original installers actually used a grinder for the entire cutout but I certainly didn't want to risk ruining $1500 of granite with an unstable wedging motion; so I used my diamond blade little 'skill saw' against an anchored thin straight edge (not the easiest thing to set up without just the right clamps etc.) to maintain stability. I believe that if pros did it for you, that they would have a cutter and an assistant to hold protective towels (and perhaps a vacuum) or whatever, rather than my cautious hung plastic all over the place.

As I recall when we installed the top+vent, the extra 1/4-1/2" wiggle room from the slightly larger cutout came in handy: we were able to shimmy the two appliances to get them perfectly aligned with each other.

chas045: Yes, the 'ears' on our vent did allow us to stabilize the vent more easily.

If we can use those fillers to close a large gap that really solves the problem. I'm feeling a lot better about getting the cooktop and vent I want. Now to visit the appliance center to pick them out and get the granite guys here for an estimate. Thanks, everyone, for your help!

If you're settled on Bosch, don't forget to look into any rebates they may be running -- seems to always be one going on. And if you missed one last month, it'll likely cycle back next month. Happy shopping!

Good to know. Thanks!