From one to many
I began with personal computers back when they still were called "micro-computers" and cost $6,000 for a bottom-of-the-line model; triple that amount for 2022 dollars. The parallel cable alone cost $100 in 1983 dollars, required to connect my Victor 9000 desktop to the Epson MX-80 dot-matrix printer ($800).
Living in North America meant that 110V-only computers weren't a problem. A good friend, moving to Israel for his higher education, had in 1985 bought a portable Compaq computer in anticipation of the move. Portable, as in "portable sewing machine size and weight" portable. He had, however, forgotten about the 230V voltage deployed in Israel. The wooden box to transport his portable Compaq and enormous voltage transformer remains fixed in my mind to this day.
Which brings me to the golden era of USB-C, where a single, thin cable connects to power, printers, ethernet networking, several kinds of displays, and external storage. Even Apple is coming around to it.
What a typical USB-C port can support
And which causes a rethink of power supplies. As USB-C becomes as universal as its name (universal serial bus), it destroys the last bastion of uniqueness hardware makers could still attack us with: the power supply, each with a unique plug-in tip and combination of voltage and amperage. I once lost the power supply to a rather useful cordless screwdriver, and so bought a package of 38 barrel plugs, shown below. Surely one ought to fit; none did.
So now a single power supply works for any computer and tablet that accepts power through its USB-C port. We can take a single power supply with two USB-C ports to charge a laptop and tablet on the road.
At home, we can replace the power bar + power cord + power supply combination so common in offices and homes with a power bar + and USB cable, such as this one shown below. We just have to make sure the power bar outputs 30W or even 100W to be able to charge laptops.
And we can slip in one more electrical element into the mix: battery backup. A single brick now can hold a big battery, and output to a couple of USB-A and couple of USB-C devices, like this one. At home, the battery acts as a natural surge suppressor, and as backup for when the power goes out.
A word about voltage and wattage
The regular USB port delivers 5V (volts) but the spec has been expanded so that modern USB-C ports can deliver 12V or 20V. In contrast, the device being charged, like a phone or laptop, draws amperes from the charger and, as the battery comes close to being full, throttles the amps to 0.
Multiplying volts by amps gives us watts. So, a power supply capable of 100W can output 5A at 20V, or 10A at 10V. Emphasis on "can," as 100W is more likely to work when you use a USB-C cable designed to handle higher amperes (the deadly part). Charging two devices will halve the Watts (amperes) available, because in this case it is the voltage that remains constant.
Batteries in modern devices contain circuitry that monitors the amps and tells the charger to cut back on the amps as the battery gets full, to help it last longer. In some devices, like my phone, I can tell it to charge slowly all night long, and make sure the phone is fully charged up by 7am. Slower charging is better for battery longevity, whether in phones or in cars.