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I recently learned about the importance of having electrical loads approximately balanced between the two bus bars in my home's panel. I was curious about my own home's situation, so I mapped all the circuits in the house. I have a Square D Homeline panel with space for 30 breakers - I believe this means that one bus bar has 16 breakers (breaker positions 1,2, 5,6, 9,10, etc) and the other has 14 (positions 3,4, 7,8, etc)

I ignored double breakers (e.g. electric oven) that connect to both bus bars. Lights are fairly evenly distributed between the bus bars, and they have roughly the same number of outlets (one has 39 and one has 31). However, it does seem that one of the bus bars seems to have a bit of a higher load either hardwired or plugged into those outlets:

Bus A (16 breakers)

  • two bath fans
  • radon fan (always on)
  • dishwasher
  • refrigerator
  • boiler
  • basement chest freezer
  • washer/dryer (dryer is a gas dryer)
  • router/modem/always-on small server
  • basement dehumidifier (seasonal)
  • garage power tools (used only occasionally)

Bus B (14 breakers)

  • microwave
  • toaster oven
  • garbage disposal
  • nighttime fans (on hot nights)

At what point is it worth making an effort to balance these loads? i.e. is there a percentage difference or an average amperage difference that is acceptable and beyond which should be balanced? (e.g. suppose on average one bus has a load that is 40% greater than the other. Or suppose one's load was, on average, 10 amps greater than the other)

It shouldn't be too onerous to balance - I would move a couple of breakers to the opposite bus. I'd try to balance similar loads (e.g. fridge on one bus, chest freezer on the other). The panel is entirely full, so I would have to switch breaker positions, but that's okay. But...maybe it's not really worth the effort?

Thanks!

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    Most of these are very small loads (100W or less) or intermittent (refrigerator, freezer, etc. cycle but most of the time should be very low usage; microwave, toaster oven, disposal very high usage but only for very short amounts of time). On the other hand, if you had some more interesting continuous loads then the answer would be "put the bitcoin miners on one bus and the grow lights on the other" :-)
    – manassehkatz-Moving 2 Codidact
    Commented Oct 14, 2022 at 14:53
  • The attempt is made during installation. After that no one GAF. It is very much not worth the effort if you aren't adding anything. If you want something to worry about, it's when someone taps a third circuit on to a MWBC and overloads the neutral, which you won't know unless you trace your entire house.
    – Mazura
    Commented Oct 15, 2022 at 1:33

4 Answers 4

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Under what conditions should I consider moving breakers to attempt to balance bus loads?

If you manage to trip your main breaker then you should assess the bus load.

If you're looking for piece of mind without waiting for your breaker to trip then verify the load using a clamp meter as seen in this video: https://youtu.be/Z1-EVv5YeW0?t=146

IF you are extremely careful and cognizant then you could take a reading on each hot leg inside your electrical panel.

It's fine to have multiple high amperage items on a single bus as long as you don't find yourself using them all at once.

If you were to have multiple space heaters on a single bus then that is one way I could see you tripping a main.

If you have an electric hot tub, electric stove, and electric dryer running at the same time then you could easily risk overloading a bus with just a microwave and vacuum.

Fridges and freezers really use about 2-3 amps when they're running. Lights? Assuming you have LEDs then those are of zero concern.

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  • Well, I haven't tripped the main breaker in 10-ish years of living here! Knock on wood! :) Are you saying it's not a problem as long as the main never trips? I have seen mention of possible overheating with unbalanced load. And yes, as you point out, my loads are fairly low amp (e.g. fans) or intermittent (dishwasher or washer running for an hour), but I would say that one bus does consistently have a greater load...
    – susie derkins
    Commented Oct 14, 2022 at 14:22
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    .@susiederkins Tripping the main is a symptom of an overloaded bus, yes. Assuming that all of your breakers are appropriately sized for the smallest wire on the circuit and you have no arcing issues then you are very unlikely to ever have an electrical issue. There is a lot of fault tolerance built into the electrical code with the 80% rule. I'll add to my answer how to verify that you're fine.
    – MonkeyZeus
    Commented Oct 14, 2022 at 14:36
  • @susiederkins See my edit =)
    – MonkeyZeus
    Commented Oct 14, 2022 at 14:40
  • Also the major consumers such as stoves, hot tubs, car charging, etc are all 240V so they go on both busses and end up as a balanced load regardless of where you put the breakers. You really have to go out of your way to unbalance a panel enough with 120V loads to cause a problem.
    – KMJ
    Commented Oct 14, 2022 at 15:12
  • @KMJ I pointed out those appliances because I really cannot think of other culprits which consistently draw a heavy load. If you have a 50-amp stove running and a 30-amp dryer in a 100-amp panel then it would be trivial to use one or two items which exceed the remaining 20 amps; regardless of bus.
    – MonkeyZeus
    Commented Oct 14, 2022 at 15:17
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You seem to have a solution looking for a problem. If the main brkr doesn't trip, you don't have any crazy odd smells from the panel, the panel isn't warm, you don't have an issue. Most home wiring/circuits are way over-subscribed, but when you look at the layout of the buses they are staggered so that one breaker (120v) goes on one bus and the next one goes on the other bus.

If you really are worried about this, for whatever reason, if you CAREFULLY use an amp clamp style meter you can measure the current draw at various times, putting the meter on one leg and then the other. BUT BE CAREFUL, YOU'RE DEALING WITH A LIVE PANEL HERE.

pic of an electrical panel

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As seen in other answers here, overloading a single stab is a more common concern than bus loading. That means ignoring the 2-pole breakers is the wrong approach to this.

If you have, for example, your range and A/C or electric water heater directly opposite, they might exceed the rated limit.

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If you have a generator your loads on it need to be balanced regardless of the total load. You should be somewhat careful about getting that right.

On utility power you do not need to "balance" loads. You can have all your 120V loads on one bus if the total load is within main breaker capacity. Your high loads are probably 240V so probably already balanced. If, in addition, you have lots of 120V loads on one bus and your breaker is tripping (or close to it) you should move some.

The utility needs to keep things balanced at a larger scale ... but they don't rely on you for that.

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