In a standard wall outlet (two three-prong sockets) do both sockets share power? Say I plugged a surge protector into one and a surge protector into the other and have 5 devices connected to each surge protector. Would that be the same as if I plugged both surge protectors in to one socket using a splitter?

I'm asking because I'm thinking of getting something like this but it only plugs into one socket, where I currently have a surge protector plugged into each socket.

Would this be ok or will it overload the outlet?

  • It is a power strip with a surge protector, and since the surge protection feature does not seem to have any relevance for the question or answers, I suggest it changed to simply "power strip". I have never seen a power strip with a surge protector in all my life in Denmark, so I put all my emphasis on the irrelevant detail when reading the question. Commented Aug 9, 2018 at 18:56

3 Answers 3


It depends. Outlets are manufactured so that both sockets are powered from a single source - one hot wire and one neutral wire and a ground wire for safety.

On almost all outlets, those sockets are connected by small tabs of brass that feeds the connections from one socket to the other. If you attach the hot and neutral wires to the screws for one socket, these brass tabs carry that connection to the other socket. It works the same way if you use the press in connections which are holes on the back of some outlets (but many pros and DIYers do not favor using press in connections). The brass tabs on the side carry the power from one socket to the other.

You can change this. If you break off the brass tab on the hot side, the hot wire you attach to one socket does NOT carry over to the other socket within the outlet. This technique is often used to have an outlet with an always live socket (for clocks, etc,) and a switched outlet (for bedside lamps). The outlet is wired with two separate hot leads, one that is always hot and one that goes through a switch. They could be on the same or different breakers depending on several factors. The neutral side may or may not be connected depending on several factors that are not critical here.

You can also separate the sockets if you wanted a dedicated socket for a high draw device, such as a heater, and run a separate line from the panel. (This generally would require a separate neutral).

In your example, if the sockets are set up conventionally, that is powered from a single line, there is no difference, except plugging into a socket is a marginally safer approach than multiple splitters. Be sure that the overall load that is likely to be used at one time does not exceed the capacity of the surge protectors or the circuit breaker on the line.

  • 3
    Your question is full of useful information, most of which does not answer the original question. That's because your answer is on-topic for the site, but the question is off topic!
    – Jay Bazuzi
    Commented Jul 29, 2012 at 17:19
  • 2
    You don't require nor should you have a "separate ground" for a split outlet. In fact I've never seen an outlet that has the ability to have separate grounds. There are other specific requirements around how to run actual wiring for this, which may mean you end up running two ground conductors because you have two separate wires or conduits, but they'd end up being connected (on both ends) anyway.
    – gregmac
    Commented Jun 24, 2015 at 18:55
  • @gregmac I beleive you are right and will edit accordingly
    – bib
    Commented Jun 24, 2015 at 21:13

In a standard wall outlet (two three-prong sockets) do both sockets share power?

The short answer is "probably". We can't be absolutely certain without opening things up a little bit.

You don't have to worry about it too much, though. Plug everything in and try it. If it doesn't flip the breaker* then the in-wall wiring is safe. The only consequence of "overloading the circuit" is tripping the breaker. It that happens, just flip the breaker back on, and find a different solution.

Remember also that many outlets, perhaps in different rooms, can be on the same circuit. You may already have load on this circuit and not know it. So again, just try it & see.

You may be thinking about adding up the load ratings printed on each device and using that to decide if it will overload the circuit. This doesn't work, as devices rarely draw their full rated load. Computer equipment is a great example - my laptop is rated at 90W, but usually draws more like 10W.

*Assuming everything is wired correctly & functioning properly.

  • 1
    Very good point about multiple outlets sharing a circuit.
    – bib
    Commented Jul 29, 2012 at 19:55
  • +1. Nit pick: if it trips the breaker, step one is to unplug something, then flip the breaker back on.
    – BMitch
    Commented Jul 30, 2012 at 0:10
  • 1
    @BMitch is right, especially because when you turn on the breaker, all the devices will turn on at once. Startup load is usually higher than running load, so you are very likely to trip the breaker immediately. So, yes, reduce the load before you turn the breaker back on.
    – Jay Bazuzi
    Commented Jul 30, 2012 at 1:23
  • Sometimes you hear stories of people turning on devices in a very specific order to avoid overloading circuits.
    – Jay Bazuzi
    Commented Jul 30, 2012 at 1:23
  • 1
    And you get specialized power strips for computers (not cheap), where they can be configured to power on with a different delay for each outlet. They're not cheap, but quite useful when you have lots of things with motors spinning up (eg, disk drives)
    – Joe
    Commented Jul 30, 2012 at 23:43

Get one that includes surge protection, like this: http://www.amazon.com/dp/B00T3QBRI6?psc=1 or this: http://www.amazon.com/dp/B018T28QNS?psc=1.

In general, try not to overload your domestic circuits.

Also, regardless of whether the sockets are sharing power, a surge protector in one would never protect the other as it is "downstream" (for want of a better word) from both of them. The purpose of a surge protector is to smooth out irregularities in the supply that could damage sensitive (i.e. computer) equipment. Any DC adapters you plug in are already doing a good deal of smoothing in their own right.

I could be wrong but you seem to be mixing up the function of a surge protector and the MCB's and/or RCD in your distribution board.

  • If the surge protector is just an MOV connected across the leads, it will protect everything on the same breaker. It crowbars overvoltage. If it fails shorted, the breaker protecting the circuit will open. (If it fails catastrophically, the device package will open and spew hot metal and stuff inside the surge protector. This is called "letting all the magic smoke out.") So a surge protector in one side of a duplex outlet should protect the other outlet also. You can wire a big one in to the mains box and protect the whole house.
    – user50401
    Commented May 6, 2016 at 1:41

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