Well, first of all, there isn’t one grid in the U.S. There’s an eastern grid, a western grid, and Texas (yes Texas has its own grid). Trying to combine them all into a single grid wouldn’t work very well.
Also, each of these “grids” is really a bunch of smaller systems that are all tied together.
There’s some debate about exactly how vulnerable a lot of this stuff would be to a terrorist attack. Theoretically, there are attacks that could pretty much make large sections of the grid go dark all at once. But the thing is, the folks at the power companies aren’t going to stare at their monitors and cry helplessly. Even in the worst case, probably 80 to 90 percent of the country would be back up and running fairly quickly. There might be extended outages in some areas for a few days or maybe a week at the most, but that’s probably it.
There’s no way for a terrorist group to actually destroy the grid to the point where they would have to string new wires and all of that. Most of the parts on power systems are simple things like wires and transformers (which are just coils of wire around an iron core, possibly in a container filled with oil). While the controls can be screwed with, which can cause systems to trip offline, the bulk of the power system is pretty rugged and can’t easily be broken.
If you are really concerned about losing power, a solar system is not the answer. Solar power only works when the sun is shining. You can use solar to charge batteries, but current battery technology isn’t all that great. You can spend a lot of money on batteries and not get that much electrical capacity for your dollars.
A diesel generator is probably your best bet. A generator capable of providing all of the power your house uses under normal conditions will also be rather pricey. You can have your home’s electrical circuits split into two panels, with one panel containing all of the critical circuits, like your refrigerator, furnace, water heater, maybe your oven, and then the other panel has everything else. When the power goes out, you switch the critical panel over to your generator using what is called a transfer switch (any permanently installed generator should have a transfer switch, whether the generator powers the entire house or just a sub-panel).
A lot of stuff in the “grid” is old. Power companies don’t replace all of their equipment every few years. That would be ungodly expensive. They buy stuff and then run it for decades. Calling it all hopelessly out of date seems a bit silly to me.
If you are in the northeast or southwest, you are much more likely to experience a cascade failure than a blackout due to a terrorist attack. The northeast and southwest parts of the country are a bit overloaded with their power systems. In the summer, when electrical usage is at its worst (due to air conditioners and such), these areas can barely keep up with the demand.
To understand what a cascade failure is, consider that your “grid” is made up of four systems, A, B, C, and D. A and B produce more power than they use. C produces exactly what it uses, and D uses more than it produces, so much so that it buys all of the surplus from both A and B. Now, let’s say that B fails. A can’t produce enough to supply all of D’s extra needs, so A gets overloaded and it goes offline as well. Now C, who can only produce what he uses, has to try to supply his own load, plus the extra load on D. C can’t do that, so he also goes offline. And since D couldn’t produce enough power to start with, his generators go offline as well. Theoretically, if B went offline, D should have gone offline as well, but then A and C would have had enough power for themselves. But since they are all tied together, the failure cascaded through all of the systems and they all went dark. To recover from that, all A and C have to do is isolate themselves from the grid, and they can start everything back up and they’ll be running again. B has to fix whatever problem it had that made it go offline, and then it gets to start up again. D can’t start up everything on its system though until all of the other guys are running though, so a lot of D’s customers stay dark for a long time.
Since cascade failures can be pretty severe, power companies have tried to improve their handling of faults so that in a case like the above, D immediately trips offline so that A and C can keep running. You don’t really know if these systems work though until something breaks. In 2003, a transmission line that was sagging due to overheating (from heavy load) contacted foliage and shorted out. The system that was supposed to re-route power and prevent a cascade failure from happening had a software bug, and what could have been a fairly localized blackout instead caused a widespread blackout across much of the northeast.
Most areas in the northeast had power later the same day. Large parts of New York City (basically D in the above example, because it consumes a lot more power than it generates) were without power for a couple of days. Minor blackouts persisted for a couple of days after that in some areas.
A lot of industry experts claim that the grid is more rugged now and this type of cascade failure can’t happen again. Yeah. Right. I’ve heard that before. And I have enough technical knowledge to know that you can’t say that for certain until you’ve exercised the system during actual fault conditions.
A terrorist attack would have similar results. Yes, a lot of stuff would go dark. Areas that have a huge electrical demand like New York City would stay dark the longest. Air travel is going to be screwed for days, maybe a week. Some businesses and financial institutions will be closed for days. But the country isn’t going to grind to a halt. People are resilient. Most things will be back up and running fairly quickly.