Service Load Calculation

Notes

• **Do not add up the nameplates.** Every appliance in this house adds to 29,200 VA, but NEC 220.82 counts **100% of the first 10 kVA and 40% of everything above it** — because a house never runs the oven, the dryer, the dishwasher and the disposal at the same second. That single step is why the honest answer is 104 A and the forum answer is usually double.
• **125 A is the code minimum; 150 A is what gets installed.** Services come in fixed sizes, so "you need 104 amps" is never an answer on its own. 125 A satisfies NEC for this load today. Most electricians fit 150 A anyway, because the marginal cost at install time is small and the cost of upgrading later — new meter base, new mast, utility coordination — is not.
• **Heating and cooling count once, whichever is larger.** Adding both is the second most common error and it pushes plenty of ordinary houses onto a 400 A recommendation they will never need.
• **Adding an EV charger later is the change most likely to break this.** A 48 A charger adds 11,520 VA before demand factors and is the single most common reason a service that was fine for thirty years suddenly is not.
• Panel space is a separate constraint from service size. A 200 A panel with every slot full needs a subpanel or a tandem-breaker plan, and that has nothing to do with the calculation above. And a licensed electrician's stamped load calculation is what an inspector accepts — this page is for knowing where you stand before you call one.