The Induction Site has a link to the Bosh installation guide.

If both models are the 800 series then the only functional difference is the hob layout. Also the 30" needs a 40AMP circuit and the 36" needs 50AMP.

I can say from experience that the 36" cooktop will fit in a 36" cabinet but you won't be able to screw it in place underneath with the supplied brackets. It'll just sit there with gravity holding it in place.

Here is a link that might be useful: Bosch induction cooktop installation instructions

You will have to call Bosch to determine if the 30" has 4400 on the large element - The details on the unit say that it does, but when you do a side-by-side comparison, the list says it has only 3600.

If you want do download manuals and install instructions with cutout size, you can get that information on the Bosch website.

Here is a link that might be useful: Bosch induction cooktops

Thank you all very much.
So even though we have a 36" cabinet, I think we are shy 1/4" to install the 36" cooktop...ack.
If the 34-7/8" requirement is strict, the sides of the cabinet, without any drawer, eat into the space.

I appreciate the links. I'm nervous about trusting the installation manual since their wattage is not clear on the 36" and varies depending on who you talk to (I called Bosch and they said the wattage is 3600 and not 4400 yet the brochure from Lowe's states 4600 W ...NUTS!!!)

We have the 36" 500 series Bosch induction cooktop. It is in a 42" cabinet and we have two rollouts underneath but nothing anywhere near the heat shield.

Is it possible to change your cabinets at this point to obtain a 42" cabinet?

On our 36", the most used burner for our non-stick pan is the front right burner, not the center, because it matches the pan's bottom better. We only use the center burner for our cast iron skillet or large multi-pot, Thus, if you still have a choice between the two sizes, measure your pan sizes and ask yourself if you do enough multiple pan/pot type of cooking to make the 36" necessary.

Thanks.
I will measure pans. I just sent off my $1000+ collection of MC2 All-clad to a friend. Now "all" I have left is Le Creuset and cast iron, with a few odds and ends.
DH checked the fusebox and we only have 40amps, and not sure how expensive the 50amp conversion would be.
All in all, it may be faster and cheaper just to get the 30" but I will find out the amp issue before I give up.

Hi. We installed a 36" 800 Bosch in November. The cost to upgrade our service from 40 to 50 amps was $450 - BUT that included the electrician putting in one new outlet in the kitchen plus installing a ceiling light fixture in the family room (both were run from existing outlets). His estimate for putting in the 50 amp line & breaker originally was $500, but it ended up to be less -- always a plus!

We went for the 36" because we did just what others have suggested here: consider how we cook and what and how many burners we use frequently. We discovered that we often use three burners at a time (pasta boiling in one pot, sauce being prepared in another -- often a skillet -- and veggies cooking in a third). So we wanted some room to do that and the right sized burners to match the pans we use.

Also, since we were going to use a downdraft (again) instead of a hood, we wanted at least one of the larger burners near the back.

Additionally we liked that the Bosch had only one of the small 6.5" hobs -- some brands had two. That's a hob we knew we wouldn't use much.

All in all, we have been very pleased with our choice.

Oh, yes, we did have to cut back the cabinet sides a bit. BUT, since prior to this cooktop, we had a 36" Thermador radiant cooktop, the cabinet had already been cut. It's lasted for 14 years with no problem. We expect to get 14 yrs from this one!

Thanks again for the feedback.
We are on a peninsula in a huge manufactured home and not sure what the regulations are for Washington State...certainly worth checking. I thought I would save the propane install extension for a gas cooktop but maybe no savings --just loss of all the cookware. Always something, no?
DH is not sure he can shave 1/4" to fit the 36 in current cabs but we are debating about redoing the whole island, so maybe we can just get 42"....I lived with a 30" stove (ge profile) in Wisconsin, so this will be an improvement even if we end up with the 30".

Thanks again!