Adding an EV charger, heat pump, or electric range to a home with a 100-amp panel often raises the question of whether a 200-amp upgrade is required. NEC 2023 offers two different ways to answer it — a calculated worksheet and an actual-demand method based on real utility usage — and they frequently disagree.

Why two methods can disagree

NEC 220.82 (the calculated method) builds your load from square footage, fixed appliances, and demand factors — it's conservative because it doesn't know your actual usage. NEC 220.87 (the actual-demand method) instead uses your utility's highest 15-minute peak reading, scaled by a 1.25 safety factor, plus any new load you're adding. Because real households rarely run every appliance at once, 220.87 usually shows more headroom than 220.82 for the same home.

The load-management alternative

If an EV charger is the only thing pushing your calculated load over your service size, a UL-listed load-management device (sometimes called an energy-management splitter) can throttle the charger's draw during high-demand periods so it never exceeds your panel's capacity. This can avoid the $1,500–$4,000 cost of a full 100-to-200-amp service upgrade — ask an electrician whether your jurisdiction and EVSE support it.

How this differs from the Panel Load Calculator

Calculover's Electrical Panel Load Calculator compares NEC 220.40 (the standard method) against 220.82 (the optional method) as a full new-load worksheet with a per-circuit breakdown — it's built for sizing a panel from scratch. This calculator instead answers a narrower, upgrade-specific question: given an existing panel and utility history, does one specific new load push you over, and can your real usage data (220.87) avoid a full recalculation? Use the Panel Load Calculator for a ground-up worksheet; use this one to decide on an upgrade.

What this calculator doesn't do

This tool estimates dwelling-unit load per NEC 220.82 and 220.87 — it does not size service-entrance conductors, perform short-circuit-current calculations, or evaluate arc-flash hazards. Local utility and jurisdiction rules on service upgrades, metering, and load-management devices vary, so always confirm with a licensed electrician and your local code authority before starting work.