I’ll offer a slightly more optimistic (and possibly more irresponsible) view. I really do understand the appeal of ED, when it has about a 21% admit rate with 7% for RD (even considering how legacies, athletes, etc., might skew things).
My D just applied to Penn this year, and she initially considered applying ED, but decided not to. I thought it would be OK, though, because of her NPC results. They gave the following required family contributions:
Harvard: 7K, no loan
Penn: 11K, no loan
Meets full need with loan schools like UVa, Northeastern, USC: 13K to 17K contribution plus about 5K loan for a total of 18K to 22K
So if she had applied to Penn ED, got in, and they asked for 11K, I would have been thrilled. If they wanted 16K (still less than the total for the “with loan” schools), that would be great. Even if they required 20K, my D would have taken out the loans and it would be similar to those other schools. And in that case, I wouldn’t have worried too much about the possibility that the extreme long shot of Harvard might have come in, or that another school might have ended up 2 or 3K less than Penn. Penn is a great school.
Now if she got in ED and Penn insisted on more than 22K (which is at least twice their NPC figure and more than any other “meets full need” school NPC figure), that probably wouldn’t be affordable. But that really didn’t seem likely. And even if it did happen, it just meant my D would have to go to one of her other options. (By the way, she didn’t get in to Penn or Harvard, but did get in at the other three schools, and their NPCs were all fairly close to the actual amounts offered.)
Here’s the point (finally!). Run the Penn NPC with the correct amounts for assets. If it gives a figure your parents say they definitely are willing to pay AND you know you can pay somewhat higher (with loans or an additional amount your parents have also agreed to) AND you won’t regret any other possible options, then maybe ED could be a good idea. As other people have mentioned, if your parents can’t (or won’t) even pay the expected amount, ED may not work out well even if you get in.