My money's on this-- the explosion of people in Africa and poorer Asian countries who have both the means and the need for cheap solar (plus batteries to go with it) will quickly far outstrip any entity's ability to keep pace by building out the grid. Large parts of western countries will soon follow.

I know I'd rather pay a reasonable up front cost to own my electrical generation capacity - which, as a bonus, can be set up almost anywhere in the world - and not have to pay a monthly fee for something I have no control over that's prone to outages at times when it's needed most.

The use of solar PV to detach from the grid seems potentially quite disruptive if the cost is even close to centrally produced and distributed power. I'm more interested in, and optimistic about, this feature than I am in the macro cost or ecological benefits of PV.

And what happens when there are 2 consecutive weeks of bad weather during winter?

There are several answers to this. The three that stand out to me are alternate power generation methods (inferior, but still helpful), designing systems with excess battery capacity, and, you know, using less energy at times when it's harder to generate.

People tend to be dismissive about conserving energy, but I expect they would think differently if they were producing & storing their own. We use way more than we need to-- some of the biggest power hogs are air conditioning and refrigeration, neither of which is necessary in the winter.

My point is: how expensive would it be to have alternate power generation, especially in cities? I think the grid isn't going anywhere anytime in the next 50 or 100 years at least.

Small generators are not punitively expensive.

It's anyway going to be an awful long time before North America stops burning fuel for winter heat.

I guess something like $500 a year is not a welcome new bill, but that would be the cost for replacing a house sized generator at a pretty short interval. If the duty cycle is low and maintenance is effective I would expect the cost to be lower than that.

22kW home generators that run on natural gas are < $5k

If we used solar most of the time and NG only some of the time we'd have made a huge dent in emissions.

What happens to the existing grid when there are 2 consecutive weeks of bad weather during winter?

Not sure where you are, but look at one of the availability maps at a NE utility (I know CT has one... CL&P?) after a major storm. Distributed generation definitely shouldn't be compared to "100% current availability"!

Most solar homes still buy power from the grid for shortfalls, and some can sell it back for surpluses.

They do now. What about when there's no grid left, or the grid that's there can't handle a sudden demand spike?

Which was the point of the OP - and can't have your grid and eat it too :)

This.

The nature of solar calls for a decentralized model, with each house having solar panels and a battery - just like most houses in the US have their own heating systems.

Big, entrenched utility companies don't like it because this would take much of their profits away. That said, the grid would not completely go away - it could still serve as a means to sell/buy extra energy if need be.

The problem with this is that the economics of our grid infrastructure and more importantly, the economics of existing generating capacity depends on it running most of the time. Imagine if you had to amortise all those fixed costs over the 5% of the time that you need them.

We do that all the time for transportation resources.