Panel Schedule and Phase Balancer
Lay out a load centre and balance the legs — with the slot pattern and the per-leg capacity rule that most people have backwards.
Circuits
Leave the slot blank to place a circuit automatically. Two-pole breakers take two positions in the same column.
Panel layout
Phase runs A, A, B, B down the panel — in pairs, not alternating singly.
A 200 A service is 200 A on each leg
Not 200 A in total. Adding every breaker together and comparing the sum against the service rating answers a question nobody asked — what matters is the larger of the two legs. A panel carrying 180 A on one leg and 60 A on the other is close to its limit while using well under two thirds of what it could deliver.
The slot pattern is not what people assume. Breakers do not alternate phase every slot; they alternate every pair. Slots 1 and 2 are on leg A, 3 and 4 on B, 5 and 6 back on A. That is what lets a two-pole breaker occupy two adjacent positions in one column — slots 1 and 3 — and pick up both legs, which is how 240 V is produced. Anyone balancing a panel on "odd is A, even is B" will make the imbalance worse about half the time.
- A 240 V load cannot create imbalance. It draws equally from both legs by definition, however large it is. Only 120 V circuits can put a panel out of balance, so those are the only ones worth moving.
- Imbalance shows up on the neutral. In a split-phase system the neutral carries the difference between the legs — nothing when balanced, and nearly as much as a hot conductor when badly out. That is exactly the case its size assumed would not happen.
- Balancing is free. Moving a 120 V circuit from one leg to the other costs a screwdriver and a few minutes with the power off, and it buys back headroom on the busier leg.
- These are connected loads, not demand loads. Nothing in a house runs at once, and a proper service calculation applies demand factors under Article 220. The figures here are deliberately pessimistic — useful for balancing, not for sizing a service.
- A panel schedule is a code requirement. NEC 408.4 requires every circuit to be legibly identified as to its purpose, at the panel itself. "Bedroom" is not enough if there are three bedrooms.
Work inside a live panel kills people. The bus and the main lugs stay energised with the main breaker off. Moving breakers is work for someone who knows how to de-energise and verify, and in most places it is work for a licensed electrician.
How to use
- Set the service rating — it applies per leg, not in total.
- List each circuit with its load, poles, and slot if you know it.
- Compare the two legs and the resulting neutral current.
- Take the suggested swap if one would meaningfully improve the balance.
Frequently asked questions
Does a 200 amp service mean 200 amps in total?
No — it is 200 amps on each leg, so 400 amps of 120 volt capacity in principle. Adding every breaker together and comparing the sum against the service rating answers a question nobody asked. What constrains you is the larger of the two legs, which means a panel carrying 180 amps on one and 60 on the other is close to its limit while using well under two thirds of what it could deliver. Balancing it buys that capacity back for the price of a screwdriver.
Which phase is each breaker slot on?
They alternate in pairs, not singly. Slots 1 and 2 are on leg A, 3 and 4 on leg B, 5 and 6 back on A, and so on down the panel. The common assumption that odd numbers are one leg and even the other is wrong on half of all slots, and balancing a panel on that basis makes things worse about half the time. The pairing is what allows a two-pole breaker to take two adjacent positions in one column and reach both legs.
Do my 240 volt circuits affect the balance?
Not at all, however large they are. A two-pole breaker draws from both legs simultaneously and by definition contributes equally to each, so an electric range and a water heater are invisible to the balancing problem. Only 120 volt circuits can put a panel out of balance, which means those are the only ones worth moving when you are trying to fix one.
What does an unbalanced panel actually cost me?
Two things. The busier leg reaches the service limit sooner, so you lose usable capacity. And in a split-phase system the neutral carries the difference between the legs — balanced perfectly it carries nothing, and badly out it carries nearly as much as a hot conductor, which is exactly the case its size assumed would not arise. Neither is dramatic at small imbalances, and both are worth fixing when the fix is free.
Are these the loads I should size a service from?
No. These are connected loads, meaning the sum of everything as though it all ran at once, and nothing in a house does. A proper service calculation applies demand factors under Article 220 and produces a considerably smaller figure. The numbers here are deliberately pessimistic because balancing is about relative loading between legs rather than absolute demand — use a load calculation for sizing.
Is a panel schedule actually required?
Yes. NEC 408.4 requires every circuit and circuit modification to be legibly identified as to its clear, evident and specific purpose, and the identification must be at the panel itself rather than in a folder somewhere. "Bedroom" does not satisfy it if the house has three bedrooms. It is one of the most commonly ignored requirements in the code and one of the cheapest to satisfy.
Can I move breakers myself?
The bus bars and main lugs in a panel remain energised with the main breaker off, because the service conductors land ahead of it. Anyone working in there needs to know how to de-energise properly and how to verify it, and in most jurisdictions moving circuits in a panel is work for a licensed electrician regardless of competence. This tool tells you what to move; it is not advice about whether to be the one moving it.
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