Most of the US utilizes the NEC for installation compliance. Per NEC, 15A-style outlets are "to code" on 20A circuits unless a single recepticle ("dedicated") circuit — in which case a 20A-style recepticle MUST be installed.
For any electric appliance (including computers) which operates for 3hrs+ ("continuously"), the circuit rating is reduced to 80% capacity (e.g. only 16A load allowed continuously on a "20A circuit" == only 1920W computers allowed on 20A circuit, 1440W on 12A).
Pro tip: check your own PSU, but practically all modern computers can handle AC input 100-240V (all you need is the correct IEC power cord for a 240 US plug).
I have fixed enough melted devices in my career to always twice-torque each&every connection I make. For temporary extension cords/plugs, "twist lock" ends are worth all the extra dollars.
Protips: use Eeez-Ox (a conductive paste which inhibits corrosion) for high-load applications (non-data, only). My own gamerig's AMD GPU has it (sparingly applied) within its dual 8-pin connectors. I supply the 8-pin connectors from a single pair of 8awg copper, which is directly soldered within the PSU's PCB power-take-offs... so only a few inches of 16awg for voltage drop (into the GPU), which reduces the amperage required (but is also unnecessary overkill).
It’s the whole chain - 20a outlets typically require 12ga wire instead of 14ga, a 20 amp breaker, and yes - the outlet is different. The 20a outlets add a horizontal opening to one of the 2 vertical slots, making a sideways T shape. Devices that require 20 amps will have one of those horizontal prongs to ensure you don’t plug them in to a 15 amp outlet.
The outlet itself doesn't care, but the shape of the receptacle is supposed to restrict insertion of a 20 amp device into a 15 amp socket. You can stick a 15 amp device into a 20 amp socket, but not vice versa. The electrician should be installing 20 amp sockets if the cabling can support it, but many don't.
20a outlets are also expensive compared to 15A ones. When redoing the electrical in the house I inherited I put a dedicated circuit in the living room for the TV/game consoles/etc since my daughter's gaming rig would be going in the living room as well; since I hadn't decided to put the recessed panel for the TV wiring in at the time it was the only outlet on the circuit and code dictates that a 20A circuit with a single outlet must use a 20A receptacle.
I can buy a 10-pack of nice 15A Leviton Decora Edge outlets (that use lever lock connectors instead of screw terminals) for $26 ($2.60 each), but basic 20A tamper resistant outlets (which newer editions of the NEC require anywhere a small child can access them) are $6+ a pop.
When nothing outside of my electrical room (where the servers live) has need of a 20A receptacle it's kind of pointless to spend the extra money on them, but the extra couple bucks on 12 gauge copper is always wise.
It has long been my understanding that a single regular, bog-standard 15A duplex (ie, dual outlet) receptacle meets the multi-receptacle requirement of a 20-amp branch circuit.
If my understanding is correct, then you overkilled it and you could have saved a few dollars, at least one welli-intentioned rant, and still have been compliant with NEC.
A literally-single 15A outlet like a Leviton 16251-W would not pass muster, while one dual-outlet example of the 15-amp lever-lock devices you mention would.
Well, the rant still applies either way - the 20A outlets are 2x the cost, that's the big reason why the aren't routinely installed. I was thinking when I embarked on the project "oh, I'll just put 20A ones everywhere because why not?" and immediately decided not to when I looked at the prices for the packs of outlets....
I had the luxury (or curse, depending) once of owning a home that needed all of the wiring replaced.
Being the kind of person that I am, I overbuilt things as I felt was appropriate. As part of that, I certainly wanted to install 20 amp outlets (even though I've never held in my hand a 20 amp plug).
The cost of that, vs good spec-grade 15A duplex outlets, was insane.
I know that the only difference is using one T-shaped contact instead of a straight and some different molds for the plastics. The line producing T-shaped contacts already exists, and so do the molds. Every 15A outlet sold today can transfer 20A safely.
It should be pennies difference in cost, and it was instead whole dollars.
Sucks.
(I'm reasonably certain that we are going to be broadly stuck with this low-current, low-voltage business until something very different comes along, and that any of this is unlikely to change in my lifetime.)
If the cheaper 14guage wire was used in the walls then only the 15 amp socket is appropriate, otherwise you might plug in a 20amp device and melt the wires or burn down the house.
Not really. 15A receptacles are required by code to be able to handle 20A of current at their terminals, so the larger wire and breaker allows for more loads to be run instead of one big load to draw it all (and if you need that, then a 20A circuit with a single receptacle does actually require it to be a 20A receptacle).
The shape of the outlet is different for different current allowances (the spades are wider or rotated). It is supposed to allow an electrician to indicate that the whole circuit is rated to handle the higher expected load, and that there aren’t other outlets on the same circuit which might also try to use the whole current available. Basically a UI problem trying to encourage robust designs for use by non-experts
