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Can I put two bathrooms on one 20amp breaker for the respective outlets or do I need a separate 20amp circuit for each bathroom? I am running out of panel space in my subpanel otherwise I would just run a home run from the subpanel to the bathroom no big deal. I am located in Connecticut USA.

isherwood
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Ron Hutchins
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  • Welcome to Stack Exchange. You should [take our tour](https://diy.stackexchange.com/tour) so you can make best use of this site. – HoneyDo Apr 19 '21 at 20:46
  • You can always get the mini breakers too so you dont have to worry about space as much – element11 Apr 20 '21 at 14:55
  • If there's some damage in one bathroom that causes a short circuit, which you can't repair immediately, you probably don't want the other bathroom to lack electricity as well ... – Guntram Blohm Apr 22 '21 at 14:00

4 Answers4

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Ed Beal's post covers a major point... here's a little backgrounder on that. A 20A breaker @ 120V will supply 2400 watts nominal. "Sounds like plenty, what could 2 bathrooms possibly use?"

Well, one hair dryer is between 1500 and 1800 watts.

So while it's perfectly legal for any number of bathrooms to share 1 electrical circuit (one McMansion was built with 5 bathrooms on 1 circuit)... it's a bad idea from a usability standpoint.

So really, decide. What is the purpose of doing electrical wiring? To serve yourselves. If you're trying to barely comply with Code to get inspector sign-off so you can flip the house, then 5 bathrooms on 1 circuit makes sense. However if you're gonna live there, then the first rule of electricity is: "It's there to serve me, and do my bidding". So install the electrical service that you want.

Now, as far as that full panel, first, if you're full it's surely less than 40 spaces. If so, it surely allows at least enough tandem/double-stuff breakers to make it to 40... so that's an option. Also, in the LED age, lighting circuits don't need the ampacity they once did - if you have several lighting circuits, you may be able to consolidate them onto one breaker.

Also, bathroom hardwired loads can be on any 120V circuit of any kind (except the dedicated circuits to kitchen, laundry, garage or bathroom receptacles, or furnace. And they are allowed on the bathroom recep circuit if that serves only this same bathroom). So it may be possible to recover spaces by diffusing those loads onto other nearby circuits.

Lastly, you can do what you really, really ought to do... and that's fit a big subpanel today so that you are ready later when you want to add other circuits. You don't want to let opportunity after opportunity pass you buy - hot tub (can't) heat pump (no spare spaces) floor heat, electric vehicle, 240V welder at a great price, have to turn 'em all down. Again back to "Electricity serves us".

Harper - Reinstate Monica
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    Thank you. I totally understand the concern posted in these answers. I really appreciate the insight as to why you wouldn't want to do what I am asking. – Ron Hutchins Apr 20 '21 at 13:29
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    This. Hairdryers are basically a short circuit plus a fan. So many people fundamentally miscalculate how much power they require. – J... Apr 20 '21 at 14:17
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    I really love how a long winded answer with no code reference gets many more upvotes than the first answers guess it shows more about nothing is how to get rep here. – Ed Beal Apr 20 '21 at 14:39
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    @EdBeal Your answer is Yes first, with the "no" caveats second. This one is NO first, with the "yes" caveats second. That's what won my vote, because while it's technically allowed, it's insane to not have dedicated circuits for hair dryers. In fact, one of the first things I did when moving into the house I'm in now, and in the previous one, was to run dedicated circuits to the bathrooms. If you live with an active hairdryer, you *will* pop breakers at some point or another otherwise. – J... Apr 20 '21 at 14:51
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    @EdBeal Good point, honestly since mine is only an *addendum* to yours, I am surprised by this situation. Hey people, +Ed's... – Harper - Reinstate Monica Apr 20 '21 at 17:07
  • Well, I +`d both too, but I do like this answer a *bit* more. – J... Apr 20 '21 at 17:17
  • Both our bathrooms are on one circuit, but it's ok, because we own zero hair dryers or curling irons, and only one space heater which we would never use in the bathroom. Not everyone's usage or habits are the same. – stannius Apr 22 '21 at 15:59
  • @stannius I would say that the answer addresses that well - but I'd say *more* important is that you should also consider future-proofing as a relevant factor. You don't *today* use more than one circuit, but another day? Or the next tenant/owner? – Joe Apr 22 '21 at 18:20
  • @Joe exactly... we get a lot of "well I don't need that" (code requirement or best-practice) but the fact is, people don't finish their tenancies at a house by tearing the place down. So their weird choices *do* affect others, and the value of the mortgage collateral, and neighborhood home prices. – Harper - Reinstate Monica Apr 22 '21 at 20:10
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The answer is yes a single circuit can supply everything in a single branch circuit

OR

The receptacles only for multiple bathrooms.

NEC 210.11.C .3 & the exception allow for the above statement in both the 2017 & 2020 code.

I have seen this code taken to an extreme 3 bathrooms only receptacles. The owner was trying to save $ and would not budge as code allowed it.

I was back adding 2 more breakers new wire at a much higher cost, 3 girls 3 curling irons or hairdryers will trip a 20 amp every morning.

Don’t go more than 2 and make sure the wife and kids are not fixing there hair at the same time because it could be close. (Only receptacles allowed in the bathrooms) no other receptacles or other devices on that branch circuit.

Ed Beal
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    WOW, Ed Beal, we said practically the same thing at the same time. My son's new home (which I've blabbed about several times here) has 4 bathrooms and we ran a dedicated 20 amp circuit to each one. Even the inspector commented, "Wow, what are planning on doing with all that power?" So yeah, totally agree. Space heaters and hair dryers take a lot of power.+ – George Anderson Apr 19 '21 at 22:19
  • Curling irons are nothing. One hairdryer equals sixty curling irons. – J... Apr 20 '21 at 14:18
  • @j... not sure where you are getting your info from maybe 6 if the small 200w round ones but I know the wave ones are closer to 500w. – Ed Beal Apr 20 '21 at 14:37
  • @EdBeal Ok, fair - flat irons maybe up to 300W briefly, but even those modulate once they're at temperature. Older irons just ran at 30W or so and stayed there. Most modern curling irons are less than 100W. Heck, a soldering iron is less than 100W and that gets much hotter than a curling iron. Irons don't typically sustain their peak draws - especially those with high peak ratings. The high peak draw allow a faster heatup, but the power dials back very quickly because an iron heats up fast at 300W. Hairdryers run at 100% output always and generally devour the entire circuit. – J... Apr 20 '21 at 14:48
  • @j... my granddaughters wave iron is 500w, 2 hairdryers and curling iron will trip a 20a there load is more cyclic but they have an impact and hearing girls squeal when the breaker trips can be irritating the 3 times in 1 morning. Let’s compare apples to apples a soldering iron 60w only heats a pin point a curling iron has many square inches of surface area to radiate the heat 200-500watts verses 60 watts not even close to the same load. – Ed Beal Apr 20 '21 at 14:56
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    @EdBeal Two hairdryers will trip a 20A by themselves. They don't need the iron's help. Two sinks, two hairdryers, two circuits. You don't have to budget for the irons if you provide a circuit for every hairdryer. – J... Apr 20 '21 at 14:57
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Yes, you can put more than one bathroom on a 20 amp circuit for outlets, but nothing else can be on that circuit other than bathroom outlets. But bear in mind that if 2 people are using each bathroom at the same time, one with a space heater and another with a hair dryer, you could easily trip a breaker.

George Anderson
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    Space heater in the bathroom? **Bad idea!** Despite GFCI (which *should* take care of the electrical safety issue) I am extremely against (just ask my family when we've had heating problems) space heaters in the bathroom - very hot object running for a while in a (compared to most rooms) very small space is **not** a good idea. Heat fan in the ceiling is a different story - totally safe as it is (literally) out of touch - and those need to be on their own circuits anyway. – manassehkatz-Moving 2 Codidact Apr 19 '21 at 22:42
  • @manassehkatz- those ceiling heat / exhaust fans never made sense to me the fan sucks all the heat out but those heaters and cable ceiling heat are quite common in the Pacific Northwest. so it is “normal” to see space heaters in baths here plug in or built in. My 30’s farm house had them built in to the wall next to the tub metal frame and all 2 wire. (Yes I removed it when I rewired). – Ed Beal Apr 19 '21 at 23:04
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    The heat/exhaust makes perfect sense when there are 3 separate on/off switches - light, exhaust, heat - with the heat fan circulating air in the room and only the exhaust fan sucking air out of the room. But when I had mine installed, I remember the packing talked about having 1, 2 or all 3 on at the same time - and of course having the heat fan and the exhaust fan on at the same time would be a waste of energy. Kind of like lining up the printer to output right into the shredder. – manassehkatz-Moving 2 Codidact Apr 19 '21 at 23:22
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    @manassehkatz-Moving2Codidact I have to disagree somewhat. Not all space heaters are created equal. Yes, those small nichrome wire heaters did get quite hot, but the newer, high-end space heaters (many have ceramic heating elements) are very safe. I have one in our master bath, it's about 3' tall, puts out a nice gentle warm stream of air in an oscillating pattern, doesn't get hot anywhere, has a "tip-over" switch in case it gets knocked over as well as a thermostat. It's really nice to have a little extra warmth in a bathroom. It's safe if you get a high end space heater. – George Anderson Apr 19 '21 at 23:39
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    George, I think space heaters are more common here in the PNW because we all know cable heat / ceiling heat sux and it was the most common method for a long time so we are used to having them. Now with heat pumps and mini splits efficiency getting the operating cost close to natural gas things are shifting that way but the bath is regularly left out so again the ceiling heater and fan combo or a space heater is not unusual for much of our area unless central air (heat and or cooling). – Ed Beal Apr 20 '21 at 04:41
  • Ed: Interesting comment +, I didn't know ceiling heat was that common here in the great PNW, I only knew of one person who had it. Seems like here everything was either a gas or electric furnace, or baseboard heat ($$$) back in the day. A few heat pumps, but not that many. – George Anderson Apr 20 '21 at 13:42
  • A combination of baseboard and ceiling heat all electric was more common up until the 80’s in several large areas bonneville dam and cheap electricity made sense to install the least expensive power hungry heating because power was so cheap. When they went nuclear and had to shut that down that raised our $/KWH but still cheaper here than some areas of the US. – Ed Beal Apr 20 '21 at 14:29
  • Yes, it was about 2-3 cents per KW. Even now at 10-12 cents per KW, we are way less expensive than California at 30-40 cents per KW. I live about 30 miles away from the failed Satsop nuclear power plant, watched that thru the 70's, they shut down construction after massive cost over-runs. It never produced a watt of power. The giant cooling towers are still there. Such a waste. – George Anderson Apr 20 '21 at 14:47
  • Never heard of a space heater being used in an indoor *conditioned* space (why not just turn the thermostat up a degree or two?). Especially for a case where you aren't in that space very long, and half the time when you're in there, you've got an external source of heat (shower/bath hot water) already. – TylerH Apr 20 '21 at 15:10
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    @TylerH, doing that would heat the whole house. It's even common now to have an electrically heated floor in bathrooms. And my wife, shall we say, takes her time in the master bathroom "preening" and likes it warm. I wouldn't want to heat the whole house up to 75 just for the bathroom. And more recently, it's become common NOT to install a heating vent in bathrooms for, shall we say, delicate reasons. – George Anderson Apr 20 '21 at 15:21
  • @GeorgeAnderson Interesting reasons. One often unforeseen issue with no HVAC in bathrooms is that that space has to get deducted from the heated/conditioned square footage of the house when you sell. Of course, heated floors might avoid that issue in colder climates. – TylerH Apr 20 '21 at 15:37
  • @TylerH I've never heard of having to deduct space inside the insulation envelope just because there wasn't a heating method there. Getting less delicate here: The reason for not putting heating vents in bathrooms is because it can "blow the stink" out into the rest of the house, not to mention moisture. Good bathroom vent fans of decent capacity would minimize or eliminate that, but lots of times people (and esp contractors), cheap out on them and get some little 50 CFM fan that doesn't get the job done. – George Anderson Apr 20 '21 at 15:56
  • That's stupid. If you're worried about "blowing the stink", install a register that can close off air flow to the bathroom if/when you want to. Don't leave the vent out of the room alltogether. In most climates that's a guaranteed recipe for mold damage - room that gets lots of warm moisture + no AC = very bad news. – R.. GitHub STOP HELPING ICE Apr 22 '21 at 19:41
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One potential gotcha here is with GFCIs. In a normal circuit, you put receptacles in series with one another. But you really don't want to do that with a GFCI where another room is on the LOAD side because if you wire them up like that, Bathroom #2 might be the trip for an event in Bathroom #1, and you might not want to have to leave the bathroom to reset a GFCI in another bathroom. If you do elect to do this, be sure to make your GFCI receptacles are on their own branch off that single 20A line. Pricier, but you'll save yourself a lot of headache having them tandem to each bathroom.

Machavity
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