Demand response is the biggest unpredictable factor, I think, but demand is also unpredictable.

Power plants are commonly depreciated over 30 or even 40 years. Electricity consumption in the US doubled during the 01960s, and it doubled in PRC during the 02010s. If the transport sector in the US went all-electric, that would double electrical consumption again even without increasing energy use.

How can you predict what fraction of your users will be using electric vehicles 15 years from now, and whether they'll charge them in the daytime or at night? That depends on, among other things, whether they'll go back to working in offices, whether the offices will have chargers, and how much cheaper it will be for them to charge during the day than at night. And that, in turn, depends on what kind of time-of-use rate schedules you can get the public utility commission to approve. Will people insulate their houses more so they don't need to heat them at night? That depends not only on the rate schedule but their future expectations of the rate schedule, as well as what their house buyers' expectations of the rate schedule. How much will superinsulating your walls raise the house's sale price?

How about home TCES — if daytime electricity is sufficiently cheap, such forms of energy storage might become popular as a cheaper alternative to superinsulation, and maybe suppress the demand for nighttime electricity further in cold areas; but we don't have any mass-market experience with them right now. Will building codes, or insurance underwriters, impede the wide adoption of TCES after the first homeowner files a massive insurance claim to replace their hardwood floor ruined by a calcium-chloride spill? Will dirt-cheap rail-shipped carnallite drop the price of TCES further than calcium chloride possibly could? Will new carnallite deposits be found, closer to large cities?

How about the future of industry? Mass PV rollout will drop the price of energy dramatically, so industrial processes that are currently unprofitable because they use too much energy will become profitable. They might outcompete more energy-efficient incumbents.

The first example of this might be aluminum replacing steel in more and more uses; today it's so much more expensive than steel that it's only used in places where its lighter weight is a big advantage, but with lower energy costs (and shorter shipping distances) it might replace steel for many more purposes. Minimills recycling existing steel might be able to fulfill the entire steel demand for quite a while — steel mills that smelt iron from ore would shut down entirely, and the 30-year-depreciated power plants built to supply those mills might find themselves without the demand they were built for. And this might happen by 02039. This is maybe the most predictable outcome of much lower prices for electrical energy, but probably won't be the most dramatic one.

So shifts in electrical demand will depend on cultural change, diffusion of innovations, regulatory capture, consumer expectations, and cost-driven substitution in the radically changed economic landscape.

The last time the price of energy dropped so dramatically might have been Watt's steam-engine in 01776. The dislocations in society that resulted would have been very hard to predict.