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Given that the following are true.

  • They are the same size.
  • They take the same amount of work to install.
  • Doubles are twice as useful.
  • Double adapters are a thing.

Why do single electrical receptacles even exist? I was looking at the plans for a house and some of the power points were specified to be singles. Is it a code/standards compliance issue? It can't be to make a house $2 cheaper, they wouldn't be worth manufacturing if that were the case.

Someone edited this to say "Receptacles". I assume that's an Americanism? Sounds very odd to me.

enter image description hereenter image description here

Standard Australian power points. They're the same size, fit in the same hole, and have the socket in almost the same point. I've seen singles mostly in older houses. I thought maybe doubles used to be more expensive, or maybe they just ran out and put a single in. But then I saw the building's wiring overlay and somebody decided - in the planning stage - that for some reason that point needed to be a single. I know it's of no real importance, but this has been bugging me for years. This is just an average room in an average suburban house. No basement pump. (Cultural note: Australian houses don't have basements. Until recently, we tended to spread out horizontally, not vertically.) There's nothing that would be damaged if the power failed. Except the fridge, and I've never seen a fridge with it's own circuit.

We live in a world where these exist.enter image description here So if single power points are supposed to be the solution to stop people plugging in two devices, someone should rethink that.

enter image description here

Spike
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    Please add the location to your question. The only single receptacles I've seen commonly used in the US are recessed for a TV (or a clock back in the day) or 220V for a window A/C unit. – JPhi1618 Feb 21 '19 at 22:18
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    Also the receptacle for an electric dryer. – Barry Feb 21 '19 at 23:12
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    How old are we talking? I remember houses where there was exactly one power socket per room, and that was considered normal. Back then there simply wasn't the dearth of powered devices. – Criggie Feb 22 '19 at 05:37
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    Single-socket wall boxes are common in many other countries where they are more compact than a double or triple-outlet: e.g. Single: https://www.diy.com/departments/267075_BQ.prd vs Double: https://www.diy.com/departments/173672_BQ.prd – Dai Feb 22 '19 at 06:53
  • How are singles twice as useful? – K.A.Monica Feb 22 '19 at 11:49
  • What are 'single receptacles'? I always seen only modular one (you just buy the modules you need), mostly BTicino 'Magic' or Vimar 'Plana' system. Both compatible with 503 boxes – DDS Feb 22 '19 at 13:08
  • You said you were looking at plans... Are you sure it wasn't referring to "one gang" (one column of two receptacles) vs "two gang" (two columns of two receptacles each for a total of four)? – LShaver Feb 22 '19 at 13:14
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    @Criggie - I think you meant there wasn't the *breadth* of powered devices; there *was* a dearth. – AndyT Feb 22 '19 at 14:33
  • @LShaver the single gang can be a single sceptical just as a double gang can be 2 single receptacles. The "gang" term is to define the with, or how many "yokes" will fit in a box. A single gang box may contain a single, double or triple receptacle. – Ed Beal Feb 22 '19 at 15:15
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    Not sure where you are but, in the UK and continental Europe, a single receptacle is, as one would expect, about half the size of a double. – David Richerby Feb 22 '19 at 15:26
  • @DavidRicherby I did not expect that. I would have, at some point. But for whatever reason, almost every electrical device in australia is the same size. single/double power points, thermostats, a light switch with one light switch, or six. Almost always the same size. – Spike Feb 23 '19 at 00:00
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    @Spike Australia's big. There isn't room in the UK for single power points to be the same size as doubles! ;) – David Richerby Feb 23 '19 at 00:05
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    @DDS I have no idea what any of those things are. We don't do boxes. Or modules. We cut a hole in the plasterboard (I think "drywall", to you.), rectangular if you're feeling fancy, but most sparkies just make a ∞ with a hole saw, pop in a small metal bracket and screw on the power point. Our building standards are fairly primitive compared to a lot of the world. Which is weird because they're still really expensive to build. A good chippie can make a lot of money here. – Spike Feb 23 '19 at 00:11
  • @LShaver Quite sure. Added a pic. Plus I would have noticed all the extra sockets in every other room. – Spike Feb 23 '19 at 00:23
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    @DavidRicherby Melbourne is 6 times the size of London with half the population. And somehow we still manage to have places that are impossibly crowded. – Spike Feb 23 '19 at 03:08
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    Receptacle, power point, (power) socket, (power/electrical) outlet, and plug (colloquial) are all terms I've heard used for the same device. Canada seems to prefer plug and receptacle. Plug it in, plug it out. – user5670895 Feb 24 '19 at 22:44

3 Answers3

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There are quite a few reasons to use a single receptacle instead of a duplex receptacle. A few that I know of:

  • Recessed for clock or behind a TV. In this case, it is sometimes easier to use with one centered receptacle instead of top or bottom of a duplex receptacle.
  • Air conditioning, range, dryer or other larger-than-usual circuit (in the US, this means anything > 120V or > 20A). I believe in at least some cases this is a code requirement.
  • Refrigerator or freezer in a GFCI-required area in order to avoid GFCI requirements (subject to local code and AHJ). In this case a second receptacle would be indication of intent to plug in additional devices rather than using a single receptacle for a specific exemption.
  • Cooktop ignition. I have this in my own house. My electrician installed a single receptacle as (a) there is no reason to ever plug in anything else inside the cabinet under the cooktop and (b) he installed it "upside down" - ground pin on top - instead of the more typical (for the US) orientation, for an extra little bit of safety (which would be awkward/confusing elsewhere but for the seldom unplugged cooktop is perfectly fine). The same logic would apply for a single receptacle for a garbage disposal.
  • Specialized sensitive equipment - e.g., medical or computer - to minimize interference from other equipment on the same circuit (e.g., there are devices that will reboot due to voltage drop if a laser printer starts printing on the same circuit, but which will be fine as long as they are on separate circuits - and any time you have an open receptacle it becomes "available" for a printer or vacuum cleaner or whatever).
  • Backup power - if you have a generator or battery backup with limited power then using single receptacles is a way to make sure that only the specified loads are on the automatically transferred circuits.

I am sure there are more reasons - if anyone has any good ones, feel free to add to this list (or make your own answer if you prefer).

manassehkatz-Moving 2 Codidact
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    They actually all sound like pretty good reasons. None of them apply in the case I'm looking at though. It's just sitting in the corner of the room on the same circuit as the one in the other corner and about a third of the house. – Spike Feb 22 '19 at 00:43
  • @Spike Weird, what did he have a surplus of those? They're worth real money.) I would map your circuits, i.e. find out which breaker powers which outlets. (I'm fond of labeling them with a labelmaker with codewords, Thor, Sif, Odin, Loki, Cap, Widow, Stark, Hulk, Etc. Whatever.) Shrug, maybe he's in a locale where you're only allowed so many receptacles per circuit and he was "over" and that was his answer. – Harper - Reinstate Monica Feb 22 '19 at 03:57
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    @Spike They don't _happen_ to be on toggle-switches in the room, do they? Being in corners, I could see them using single-receptacles for wall-plug outlets on a light-switch to avoid confusion about which outlets in the room are on the switch and which are not. – Der Kommissar Feb 22 '19 at 16:50
  • @Harper I always assumed there should be a limit, but when electricians here wire in new power points I've never seen them check *anything*. They just grab the first cable they see and get cutting. They definitely don't go and count how many points are on the circuit first. – Spike Feb 23 '19 at 00:32
  • I've seen a double outlet get replaced with two single outlets before. Presumably, fewer wiring changes are needed compared to adding another separate outlet to the circuit. I've seen this most often when one of the singles is a special-purpose outlet (e.g. mounted on the floor instead of the wall, or dedicated to an appliance with an outlet-blocking wall wart). In OP's case, someone may have really needed an outlet on the other side of the room and wired it up the easiest way they could find. – bta Feb 23 '19 at 03:39
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    Also add dedicated switched outlets, such as for plugged in (rather than direct wired) garbage disposals. – simpleuser Feb 23 '19 at 18:20
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enter image description here

Single receptacles are used for reasons

Nobody installs one of these by mistake - they're a lot more expensive, to start with! When you find one, it has a specific purpose for being there because of a Code requirement for its application.

  • It may be in a place where GFCI protection is required, but it is appropriate for this individual load to not be GFCI protected. An example is a refrigerator or freezer in a basement or garage.
  • It may be effectively a dedicated circuit, provisioning power to a single large appliance that needs the entire circuit's capacity. An example might be a large window air conditioner, dishwasher, or built-in microwave oven.

In these cases, providing only one socket is on purpose. It is to prevent you from using the circuit for anything else.

Now, you may know that every room is supposed to have receptacles at certain intervals, (12' in most rooms, 4' on kitchen countertops). These special-purpose receptacles won't count, so you should find a normal receptacle nearby.

Harper - Reinstate Monica
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    Distance from a receptacle is 2' & 6" or 4 ' & 12' between. I know you know this but interval would be 4' in kitchens and 12' in other rooms. – Ed Beal Feb 22 '19 at 15:10
  • What's the T shaped hole all about? Never seen that before. – Spike Feb 23 '19 at 00:29
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    @spike that is keying. The vertical part allows common NEMA 5-15 plugs. The horizontal part lets in NEMA 5-20 plugs, which have different keying so you cannot plug em into 15A sockets. – Harper - Reinstate Monica Feb 23 '19 at 01:00
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    This answer is incorrect for NZ/Aus at least. – SomeoneSomewhereSupportsMonica Feb 23 '19 at 02:23
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    @SomeoneSomewhere OP didn't specify. Long after I wrote my answer, he added localization. I couldn't have known. Edits which alter the question so basically are discouraged on SE for obvious reasons. Anyway the "cost" thing is correct, they spent extra to use singles. Has to be a reason. – Harper - Reinstate Monica Feb 23 '19 at 11:42
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    @Spike by the way, Australia has the same deal with differently keyed plugs and sockets. On your 20A sockets and plugs, the power pins are taller. So a 10/15A plug will fit in a 20A socket, but not the other way 'round. . North America couldn't do "taller" because we use that for hot/neutral keying. – Harper - Reinstate Monica Feb 23 '19 at 11:55
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    My experience is that there **is** a cost saving with single sockets. It's not big, but it's there. On the order of 25% trade price. Remember, our sockets have switches, shutters etc, and a single horizontal and vertical socket use the same parts on a different front plate, whereas doubles have to be special. That number is a lot smaller than it used to be, back when double vertical sockets were two single socket mechs that had to be separately wired. – SomeoneSomewhereSupportsMonica Feb 24 '19 at 05:12
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Sometimes a single receptacle is installed to ensure that the circuit is dedicated to a single appliance. For example, you might install a single receptacle for a sump pump in the basement. If you install a regular duplex receptacle, someone might use that second receptacle and trip the breaker. Nobody notices and the basement floods because the pump is offline. Other examples where a single receptacle might be a good idea: refrigerator or storage freezer.

batsplatsterson
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