[quickthrowman]

Breaking the tabs on the existing receptacle prevents one from having to use a jab saw or multitool to cut a hole in the gypsum wallboard or plaster and install a cut-in/old work box to add a 2’d duplex receptacle: https://www.homedepot.com/c/ah/how-to-install-remodeling-box...

Any 15A or 20A duplex receptacle can have the tabs broken to get two separate 15A or 20A simplex receptacles, you don’t need a 5-20R for that, a 3-wire 5-15R works just fine.

Someone upthread mentioned 1.2kW load which a 15A receptacle handles just fine: .8*120*15=1,440W continuous. Bumping that up to 20A only gets you an additional 480W of continuous load: .8*120*20=1,920W. A continuous load is one that runs for 2 hours or longer, the overcurrent protection and wire must be upsized by 1.25x (or derated to 80%)

Most receptacles in homes are wired with 14/2 romex which is only good to 15A (in homes, which use the 60C ampacity column) which is why I suggested pulling another run of 14/2G romex and breaking the tabs. Pulling 14/2 romex to an existing receptacle usually isn’t that hard if you have a fish tape.

AFAIK computer PSUs can’t easily use 240V power without a PDU in the middle, but I’m likely wrong on that, especially for server PSUs.

[jmalicki]

Almost all computer PSUs I have ever seen are 110/220 since they don't make different models for Europe.

[quickthrowman]

Gotcha, that would make sense. In that case, your suggestion of a 240V outlet is best. Swap the outlet for a 240V one, swap the breaker out for an 240V 2-pole, and use the same wire, assuming the wire is already big enough since you won’t need a neutral.