Is My 200A Panel Overloaded? Do the Math
A 200A 120/240V service delivers 48,000 VA, but continuous loads are limited to 80% โ plan around 160A usable. With an existing calculated load of 80A, you have roughly 80A of headroom: enough for a 30A dryer, a 20A shop circuit, and lighting, but a 50A EV charger plus electric range needs a proper load calculation first. Here is how electricians stack it.
Step-by-Step Takeoff
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1
List every load at nameplate watts, or read the existing calculated load (80A example).
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2
Total existing load in amps at 240V: 80A example leaves 200 โ 80 = 120A of breaker space on paper.
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3
Apply demand and the 80% continuous rule: continuous portion must fit under 160A total service.
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4
Add the new circuit at nameplate: EV charger 50A + dryer 30A + shop 20A = 100A new on top of existing.
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5
Compare: 80 existing + 100 new = 180A < 200A service, but check the continuous slice against 160A โ shed or sequence loads if over.
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6
Balance big 120V loads across both hot legs so neither leg overloads first.
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7
Model it exactly in the Electrical Calculator panel-load panel, including GFCI/AFCI breaker requirements.
Guide FAQ
Does a 200A panel give 200A per leg?
A 200A 240V service is 200A per hot leg, 48 kVA total; balance large 120V loads across both legs.
When do I need a service upgrade?
When the calculated load (with demand factors) exceeds the service rating, or the panel is full with no listed tandem space.
What size wire for a 50A EV charger?
6 AWG copper on a 60A breaker for continuous 48A charging (80% rule on a 60A circuit).
Can I add a subpanel instead of upgrading?
Yes if the service has headroom โ a 100A subpanel off a 200A service is routine.
Do tandem breakers add capacity?
No โ they add spaces, not amps. The service calculation governs regardless of slot count.
Related Guides
Voltage Drop on a 100 ft Wire Run: Fix It by Upsizing
The 2KIL/CM formula worked for 100 ft at 120V, upsizing rules, and the 60 ft threshold.
How Many Wires Fit in 3/4" PVC Conduit?
The 40% fill rule worked: THHN areas by gauge, derating limits, and conduit upsizing calls.
What Wire Size for a 20A Branch Circuit?
12 AWG copper on a 20A breaker: ampacity, the 80% continuous-load rule, and when to upsize.