How many things can you safely plus into one outlet?

[ca1ore]

True but most outlets and breakers are only rated for 15 amps, not 20. 20 Amp recpiticals look different like this one https://www.homedepot.com/p/Leviton...I-Outlet-White-4-Pack-M42-GFNT2-04W/305340194
Replacing a 15 with a 20 is not really a solution as the breaker is still going to be a 15 amp one and replacing it with a 20 amp is asking for trouble, as the wiring between it and the recepticals is only rated for 15 amps. If you need more than 15 amps devide your load between 2 circuits or have and electrician run a proper 20 amp circuit.

As somebody noted, there is an exception in the electrical code which permits 15A receptacles on 20A circuits if there are two or more sockets on the circuit. (NEC 210.21B3). You make a good point, however, and I should have noted in my original post. I only use the 20A rated outlets on circuits that power my tank (and stereo). What you don't ever want to do is put a 20A outlet on a 15A circuit with 14 gauge wiring.