It can't be cheap/effective enough to provide power at western service levels, but it can within developing world budgets be cheap/effective enough to provide useful levels of power.
The key point here is just a restatement of Christiansen's "Innovator's Dillemma": a new product incapable of meeting the needs of most users of an incumbent product, but capable of meeting the needs of some other related market.
I suspect we're having a difference of definition.
When Christiansen is paraphrased as saying solar won't become a big deal in the US, I took that to mean "not a big deal, in total", whereas everyone else seems to be reading it as "in comparison to fossil fuels".
The "Innovator's Dilemma" describes the common scenario where the successor to an incumbent product is, when it's introduce, inferior to the incumbent on important axes; for instance, it could have inadequate storage, or be too slow, or not be secure. But the new product has attributes that make it way more attractive to some new market; for instance, maybe it's game-changingly cheap, or portable.
As a result, the new product won't be adopted by the core market for the incumbent product. It's used by a different market, or at the margins.
The "dilemma" here is, over the long term, the new product improves as it captures more and more market share. The new product has room to evolve and isn't locked into a core market with fixed expectations. Eventually, the benefits of the new product exceed those of the incumbent product, even for the incumbent's core market, and the incumbent product loses.
This all plays out in slow motion, so that even if the incumbent sees this happening, they can't do much, because they're dependent on the revenue from their core market.
Put fossil fuel in the "incumbent" box, "solar" in the "new product" box, "the industrialized west" in the "core market" box, and "the developing world" in "the new market" box.
PV is not efficient/cheap-enough to catch on in the developing world, yet.
As the developing world cannot subsidize/commodify something it cannot afford, by definition, the only way PV becomes more efficient and more inexpensive, is by chasing western demand/subsidies.
Which then means that for PV to ever be big in the developing world, there is a precondition of substantial generating and production capacity for PV in the developed world.
Given that such installations must exist for PV to even make progress toward the developing-world-changing tipping-point, it seemed strange to me to say that Solar will never be "a big deal" in the developed world.
One could likely do the math and determine approximately how much installed generating capacity and how much production capacity the industry would need to have created, to drive price-per-watt down to rates that are attractive to the developing world. And I'm thinking the numbers you'd come up with amount to "a big deal" by any reasonable objective measure.
(Though I do concede that such a substantial number may still pale in comparison to fossil fuel usage in the developed world.)
The newcomer technology displaces the incumbent by making a concession the incumbent can't make.
Here, solar can, in the developing world, make the concession of providing less power, less reliably. Since the developing world often lacks any power, bringing reliable high-output power to a region is likely to be more expensive than bringing in low-output, low-reliability solar.
Maybe you already get that, too, but I don't see you addressing the point in your comment.
I'm not addressing it because I don't have any objections to it. I understand and concede that PV can/will become attractive in the developing world long before it becomes (if it ever does) attractive in the developed world.
My objection is to the casual dismissal of the quantity of PV build-out in the developed world that's implicit in PV reaching the cost/efficiency tipping point for the developing world.
e.g. It takes an awful lot of people buying panels at $2/watt for them to ever hit $1/watt. And though, say, Africa may go on to generate a much larger percentage of their power from $1/watt panels than the US ever will, I don't think it's fair to say the big pile of $2/watt panels is "not a big deal" in the US.
The key point here is just a restatement of Christiansen's "Innovator's Dillemma": a new product incapable of meeting the needs of most users of an incumbent product, but capable of meeting the needs of some other related market.