I have a 30" builtin which is just fine for us (3 adults). If you only shop once a week or less, maybe not - we have a supermarket in the neighborhood, so often pick up dinner on the way home (that said, our fridge is rarely even full, except for condiments and drinks).

We had a 24 x 24 inch 10 cubic foot LG model in our first house and it was definitely big enough for us--family of three (two adults and a toddler) at the time. I shopped once a week, but did occasionally pick up more milk, etc mid-week. I have never had a built in so I can't really translate how that space compares, but I thought the data point might be helpful for you.

It depends on your shopping habits. Also, if you entertain a lot, you may want more capacity. Still, for most families of 2, a 30" built-in should be plenty.

However, I would make sure you know what you're getting into before you buy a standalone icemaker. There's the whole drain situation, and then there's the fact they are resource hogs, and they can also be quite noisy. IMO they only really make sense for someone who goes through lots of ice frequently, which most households of 2 probably don't. Ice that doesn't get used immediately will melt away, and they run constantly to make new ice.

We had a fridge that size for 15 years with a family of four. We did have a chest freezer in the basement and couldn't have lived without that, but I never really thought we didn't have enough room. We are going with a 36" when we remodel, but mostly because we'd like to entertain more and I think having a larger fridge will make that easier.

We're empty nesters' and I shop almost daily, love our 30" Liebherr! Our small kitchen would look silly with a large refer. Although we do have a garage fridge for beers, soft drinks and occasional overflow, but could get along without it...

How the inside is arranged, in terms of holding the right amount of the right kind of things, is just as important as the size of the fridge. Also, if you don't have room for five jars of sourdough starter (which I have in my fridge), you dry most of them and just keep on. You limit the number of different kinds of mustard that can stay in the fridge, and how much space is devoted to cold beverages (putting that ice machine to work instead).

You didn't say how many people or how big the appetites or how you entertain, but, as with all things, you adapt. A lot of people have way more fridge space than they actually need--as in never come close to filling up. Others really do use all their main and pantry fridges and wine chiller and ice machine and snack center fridge and coffee bar fridge to capacity.

A good way to judge if you can fit your current lifestyle in a new fridge is to gather a bunch of containers and bottles that are the size and shape of what's in your fridge right after you've bought groceries on a typical day, skipping things you'd rather not see again, like the jar of chocolate sauce that no one has touched in three months (if it won't fit in a smaller fridge it'll be thrown out), and take the containers to the showroom to see how they fit. You might find that the fridge you're looking at will hold everything that you want in your fridge, easily (probably so for the SZ), but you might find that while you can fit all three open wine/juice bottles, there's really no room for several eggplants along with the rest of your produce. :)

We are a family of 4 and have had 30" Liebherr for 12 years now (well, youngest is only 7 so at the start we were fewer in #), no other fridge or freezer in the house. It has worked well for us, but we will get something larger in our upcoming move (I will have 2 teenagers and their friends soon...). It depends on your habits-- we do cook a LOT, so we are not undemanding. But we are different than typical North Americans probably, in a few ways: 1) we don't need a ton of room for a lot of beverages. We do store milk (two kinds always, actually), beer/wine, a juice or two, and it has been fine for all that. But some families want all this, plus sodas, and other things, just in the beverage category...; 2) we do store a lot of bulky veg and need good veg storage: bunches of kale, chard, lettuce, huge bags of carrots, celery etc. are always in there. We do store a LOT of veg actually! We do store nuts, vitamins, some condiments, cheeses, also. So I guess we do cram a lot in there! Our fridge is well laid out for the size, definitely. But we don't use a lot of freezer space, and on the freezer part, ours is limited by NA standards, definitely. If you keep frozen foods-- we don't really, just peas, corn, berries, ice cream and ice, mostly-- you might find limitations here.

I already answered above, but the short answer I think is: yes! for the two of you, absolutely. We have put a ton in our 30 inch.

I'm coming a little late to the game, but I also have a 30" fridge - I think it's 18 cu ft. There are 3 of us. I wish I had more room, but I make do. I didn't want to give up cupboard space to get a bigger fridge. I do shop more than once a week. Like lapsangtea, we don't need a huge space for beverages. We buy milk in quarts and soda or seltzer in liters, and we still have room for wine, juice and a few beers. When I entertain in the cool months - which is more than half the year around here - I use the garage as backup fridge space.