I'm happy with Superchargers; they are fast enough for me for occasional road trips. And I'm fully prepared for Tesla's demo to be just that - "see, we can swap packs if we want." I don't feel a burning desire to have swapping available, and I'd also rather not see Tesla spend a lot of capital building out a network if it doesn't work out financially for them.
But I can definitely think of ways for swapping to be useful; and there have been numbers showing it might not be a money-loser (though it sure doesn't seem like a profit center! We really don't know enough to say for sure how the finances will go) if combined with grid storage et al. Some swapping scenarios have been pointed out in other threads. Off the top of my head:
1. If the pack you get is much bigger than the pack you already own, I see a lot of value to swapping in a big pack before (or during, depending on the nearest swap location) a trip, and getting yours back at the end. Enough for the owner to pay for it, even though Superchargers are free. With a 500-mile pack you could skip Superchargers and cumulative saved time could be significant. More important, you could go more places where there aren't Superchargers. For example, in WA and OR there are many trips I will never be able to take with a 300-mile pack and the planned Supercharger stations (at least, not without charging for many hours at 30A) - but I could with a 500-mile pack. Having the ability to take this type of trip is really important to current and prospective owners. In my state and a few others, Tesla could provide it with a CHAdeMO adapter. But the ability to swap in a 500-mile pack could be even better (assuming the swap locations are convenient). I'd be willing to pay a fair bit for a CHAdeMO adapter, so if this plan is flexible enough I'd be willing to pay for it instead.
2. If 85kWh packs are swapped, several people have focused on trading in "their" pack and possibly getting a worse one back. Of course they could always save yours. But even if they don't, why not focus on getting a better one back? As long as the packs in circulation meet a minimum criteria, what you get is not a big deal. And in fact it turns in to a big plus if it's, say, an 8-year subscription program and you can swap as many times as you like during the subscription - and get a brand-new one at the end (even if you only get that by swapping repeatedly until you get a "good" one). And perhaps the one you get at the end is also bigger than what you have now - whatever size they are selling with cars then - all included in the subscription price. Of course price matters, but if swapping for for road trips any time I like plus getting a new, larger pack in 8 years is part of the deal, I would probably pay a $12k fee. If Tesla can cover swapping prices now with grid fees (which seems really tough, but not impossible), and spends less than $12k building me a pack 8 years from now and has had my money all along, they could come out ahead.
3. As aaron0k just pointed out, this could enable a lot of people without a good charging garage to go EV.
4. Fleets. (Not that I think they're going to do that...just pointing out an area where swapping can make sense).
5. Part of whether adding a swap network to the Supercharger network is "worth it" or not depends on Tesla's mission. If they are just trying to make money selling their own cars, it does seem like right now they are selling all they can build and that swapping is not necessary - at least not yet. But what if Tesla is serious about their mission being to speed the transition to electric propulsion? As Citizen-T pointed out in another thread, while Model S owners may be happy with Supercharging, there are millions of ICE drivers that are thrilled with the idea of pack swapping. The fact that charging is slower than getting gas is the only real downside to EVs - what if the only real objection was removed? It could get them to finally consider EVs and demand them from other automakers. In fact, those automakers, in a hurry to come out with something, could license Tesla's drivetrain as well as the Supercharging and swapping systems. Tesla can probably scale up faster providing those than they can just by selling their own cars.
It all depends on details, and we're missing enough information that we can't guess the details. It's entirely possible that none of the above will work out. But they are possible, so I'm happy to see what Tesla announces before I insist that it makes no sense.
