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The measured or calculated current draw on Phase A.
Read all three phases at the SAME moment. A clamp meter taken round the panel over ten minutes describes three different buildings, and the imbalance it reports is mostly the time of day. If the panel is not energised, add up the connected single-phase loads assigned to this phase from the schedule instead — that is a design figure rather than a measurement, and it will not include what somebody plugged in last week.
The measured or calculated current draw on Phase B.
Enter what B actually draws even if you expect it to match A. The entire output of this page is the SPREAD between the three, so a figure copied across from A does not balance the panel — it hides the imbalance. Where a panel genuinely feeds nothing on a phase, enter zero: a real zero is information, and a repeated value is not.
The measured or calculated current draw on Phase C.
The one most often mis-recorded, because it is read last and sits furthest from where the meter is usually clamped. Imbalance is judged against the AVERAGE of the three, so an error here moves both the average and the deviation and overstates the problem twice. Motors are the loads that care: a supply a few per cent out of balance pushes a motor's current further out still, and the extra heat comes off its service life.
Phase load imbalance
9.756 %
- Average phase load
- 41 A
They open the calculator with your figures already in it
Three-Phase Electrical Panel Load Balancing Calculator: 9.76 % — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Phase imbalance percentage = (maximum deviation from average phase load ÷ average phase load) × 100, the standard method for checking how evenly a three-phase panel's circuits are distributed across its phases
Inputs used
- Phase A Load (A)
- 40
- Phase B Load (A)
- 45
- Phase C Load (A)
- 38
Intermediate steps
- Average phase load
- 41 A
What this calculation does not cover
- Current imbalance is not voltage imbalance, and motors care about the second. A small unbalance in supply VOLTAGE produces a far larger unbalance in a motor's phase currents, commonly six to ten times as large, which is why NEMA MG-1 caps voltage unbalance at 1% before a motor must be derated and treats 2% as already costing winding life in extra heat. A panel whose feeders are evenly loaded can still be delivering out-of-balance voltage; that check is made with a meter across the phases, not from this arithmetic.
- One reading is one moment. Circuits are balanced against loads that come and go - a kitchen at midday, chargers overnight, a chiller in August - so a panel reading 5% during the survey can be at 20% eight hours later, and shuffling breakers to flatten one snapshot can make the daily peak worse. What matters is the balance at the time of maximum demand, which comes from a logged reading over days rather than a single clamp.
- Balanced phases do not empty the neutral. On a four-wire wye panel feeding electronic single-phase loads - LED drivers, switch-mode supplies, small drives - the third harmonic and its multiples arrive in phase on all three legs and ADD in the neutral instead of cancelling, so a perfectly balanced panel can run its neutral hotter than any phase conductor. Nothing protects the neutral against that, and nothing on this page will show it; it takes a true-RMS measurement of the neutral itself.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Phase imbalance percentage = (maximum deviation from average phase load ÷ average phase load) × 100, the standard method for checking how evenly a three-phase panel's circuits are distributed across its phases
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