You will want to have some space between them. First, because the induction cooktop installation directions may require cabinet walls at the ends of the space under the cooktop, and second because the induction ceram glass surface needs to be relatively evenly supported on all four sides. A third reason would be to ensure that the countertop itself is adequately supported. All of these reasons could be overcome by an atypical cabinet structural design (probably involving metal support). A fourth reason could depend on whether pans on each surface might crowd one another.

Note that one doesn't normally shake pans on induction cooktops (not good for the glass), whereas cooking on gas can involve more physical pan action. More room around the gas burner might be helpful in such cases.

There may be manufacturers that support proximate installation, but I have never researched this.

I have a 36-inch induction cooktop next to a Cooktek induction wok hob. The exposed countertop gap between them is 5 inches. To fit this configuration my hood width is 66 inches, wider than you require. Your hood, however, should ideally be sized so that given the final layout of the cooktops, there is sufficient overlap of the hot pans on each to capture the rising and expanding cooking plumes. Presence or lack of cabinets to the sides of the hood helping direct the effluent can make a difference in capture efficiency.

In an island configuration with a hot pan at the edge of the induction cooktop opposite the gas burner side, I would go to a 54-inch hood. With a 48-inch hood, even on a wall, I would consider placing the pan to cook the most greasy smokey food towards the middle of the hood.

kas

Yes to everything Kas said about supporting your cooktops and counter. You might possibly be able to rig up some kind of welded metal structure to hold everything up and have them close together, but I've never heard about anyone doing it. I have a 15" gas and 24" induction under a 48" hood and that works fine. The space between is about 4" but the cabinet (drawers) underneath run the full 48". You might be able to get away with more like 2" unless your counter is stone. Crystaline stone, like granite, would be likely to crack even if fully supported by a heavy wood substrate. Additionally, your cooktops, given at least 3" between, would be out to the edges of the hood, which cuts the hood function. Is there any way you can grab another few inches for the hood? Wolf now makes a 24" induction on 30 amp, which might be an alternative. Remember, you're supporting the weight of the contents of the pots (even if you don't currently make your own stock, you should be able to put five gallons of water on either cooktop).

I think I will probably just get the 36" bosch flex induction or I could stick with gas & get the capital cularian 36" range top. Not sure what to do!

After reading pillog's comment about supporting the two cooktops and adding in the weight of granite, I am about to give up on having both induction and gas. All for a wok! I have no idea how to structure the cabinets in an island to support two cooktops. Are you saying if I wanted a 24" induction with a 15" gas with a granite countertop that there needs to be more support underneath? Not sure of cabinet widths but would a 48" cabinet be required and, if so, is the space underneath usable?

Perhaps I will post the entire dilemma in Design and see if someone else can make this work... I thought a new kitchen would be easier!

That's why you hire a KD.

I am working with a KD at the company our builder uses but she didn't ask me any specifics about the cooktop and I didn't realize if I had two that there would be other considerations. Now I know!

Hate to say it, but you're working with a cabinet salesperson, not a KD. A KD would be all over asking for the appliance specs before doing any real design work.

I'm sure you are right.

You can put one cooktop in a suitable cabinet and another cooktop in a suitable adjacent cabinet. Each cabinet will support the granite above it, so long as reasonable effort to achieve flatness of cabinetry is applied. For each individual cabinet, there may be some advantage to wood or steel reinforcement of granite where it may be narrow.

kas