A group of scientists has been slaving away largely in obscurity for two decades, with very few publishable results. Suddenly, one of them has an epiphany, which turns out to be instrumental to enabling them to succeed at what they are attempting to do. This happens around year 2020 or so, on Earth, inhabited by humans. We are talking about the scientific Holy Grail.
The scientists have figured out a way to make net-positive-energy cold fusion possible. The process can run on ordinary tap water, and provides enough energy to power itself as well as leave some energy for other uses.
What's more: in retrospect, the process turns out to be scientifically sound, is repeatable, and is scalable. (The exact workings of the process are not relevant to this question, and are left as an exercise for the reader.) A patent is quickly filed for and approved essentially world-wide, and the details of the process get published in the scientific community. It is a truly world-changing event.
After some 15-20 years of refinement and miniturization, the technology has been refined to the point where it can be delivered in a box approximately the size of a large refrigerator, can run on any kind of dihydrogen monoxide (with or without a reasonable amount of contaminants, so can run on both tap water and sea water), is no more dangerous than most household appliances, the technology has a proven track record, and a reasonably-sized unit (think the size of a pair of large refrigerator and freezer) can deliver a net of a few dozen kilowatts of electricity. An outside source of electricity is required when turning on the unit, which can be provided either from electricity mains or from a rechargeable battery; both types are manufactured and sold.
At this point, household units in 10 kW and 25 kW rated sizes are available for approximately the price of a brand new, nice utility car (think somewhere in the range US$ 50k-100k plus inflation), other sizes are available as well to individuals, and industrial units capable of substantially higher power outputs also become available but at a much larger cost and physical footprint; the cost of the unit rises slightly slower than linearly when plotted against the unit's rated power output, and the volume of the unit rises roughly linearly with rated output. One of these units can be expected to keep working with minimal maintenance for 15-20 years in a household setting, and can be connected directly to the water mains or refilled manually. (For comparison, this works out to a cost of about 3-4 cents plus inflation per kWh delivered for the household-type units around year 2040, plus the cost of water.)
In earthly settings, the amount of water consumed by the process is small enough to not really be significant, but the requirements are large enough that energy considerations are still important in non-ground-based operations (and spaceflight in particular). Hence, in practice, this technology reduces (and moves up front as mainly a capital cost rather than an ongoing cost) but does not eliminate the cost of electricity. Because a large fraction of the cost is an upfront capital cost, the effective cost per kWh rises if the unit is used below its rated maximum power output, but because the larger units are more expensive, there is an incentive to purchase a smaller unit if that is deemed sufficient (and then not have to replace it). In principle, multiple units can be connected in parallel to provide both additional power as well as redundancy, but for technical reasons this is rarely done in households.
Given that the capital cost up front of one of these units is fairly high but not insurmountable for a large fraction of (but not the entirety of) the world's population, that smaller units are more affordable up front, and that they can provide a reasonable amount of electrical power for a single household at little ongoing cost and with little maintenance:
- What is the short-term and medium-term (up to a few decades, say 2040 through 2080) effect on private individuals and households?
- What is the short-term and medium-term (up to a few decades, say 2040 through 2080) effect on industries and production?
Answers should focus on how electricity is used within the society. Well-reasoned, logically and scientifically sound answers please, but scientific citations not needed.