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I've searched the answer which seems to be 1800W (120V x 15a) but it's not clear to me whether the rating is for each of the two outlets or the pair together.

So I would like to know: what is the maximum for each outlet and what is the maximum if both are in use simultaneously?

  • I'm from Germany, so can't give an answer but a hint: where is the fuse? Here are often many more than just two plugs on a single fuse, and the fuse is what limits the total current for them combined, if only one is used it can use all current. – Arsenal Aug 26 '15 at 17:52
  • This is a good question. A duplex outlet can be wired so each individual outlet can be on their own circuit. So is it 15A per outlet or per Assembly? – cde Aug 31 '15 at 3:52
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The limit is imposed by the circuit breaker, and is common to all outlets in a chain. There's no limit defined by the NEC as to the number of outlets on a single circuit.

So: the limit is for the pair of outlets and beyond.

For continuous loads (e.g. heaters) code maximum is 80% of the breaker value. For things like a vacuum cleaner, you can go right up to the limit.

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No single plug-connected item is permitted to draw more than 80% of the rating of the circuit. That would be 12 amps for a 15 amp circuit and 16 amps for a 20 amp circuit. You will not find item sold with a 15 amp plug that draws more than 12 amps or an item with a 20 amp plug that draws more than 16 amps. However, there is nothing to prevent 15 or 20 amps of load from being connected through a power strip. Also, 15 amp outlets are permitted to be used on a 20 amp circuit. That would indicate that each individual 15 amp outlet or pair would need to be capable of 20 amps.

Edit: What is permitted is stated in the National Electrical Code, article 210. The use of 15 amp receptacles on a 20 amp circuit covered by Table 210.21(B)(1) and the 80% limitation is covered by paragraph 210.23(A)(1).

Re answer by Bryce The main answer is direct and to the point, but the last part is not true. NEC Excerpt

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The current / power rating applies to EACH of the outlets in a duplex receptacle. That is: you can draw the full rated current for the circuit from any one outlet in that circuit.

However, you must not exceed the maximum current rating of that circuit. If one outlet is drawing the maximum current allowed, then no other outlet on that circuit may be used.

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There are restrictions that all occur simultaneously. You are limited by the lowest of these.

  • A NEMA 5-15 receptacle is limited to 12A per socket. A 5-20 receptacle is limited to 16A per socket.

  • A NEMA 5-15 duplex receptacle is limited to 20A per receptacle.

  • 5-15 receps are allowed on 20A circuits if there is more than one socket on the circuit.

  • A 15A circuit is limited to 15A from all loads. A 20A recep is limited to 20 amps.

  • Appliances which are continuous loads must be treated as 125% of their actual load, so a 12A appliance must be treated as 15A. This is the same derate as the 80% derate most people talk about. The advantage of 125% is it lets you figure it per appliance so you aren't paying the derate on an appliance that's not actually continuous.

  • Underwriter's Laboratories publishes a White Book with their own requirements for devices. These are separate from NEC. For cord-and-plug connected appliances using a NEMA 5-15 plug, they limit current draw to 1500 watts (12.5 anps).

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