Load calculation
The math an electrician does to check whether your panel can safely add a big new circuit.
A load calculation totals up the electrical demand of everything in your home — heating and cooling, water heater, range, dryer, and general lighting and outlets — and compares it against the rated capacity of your [service panel](/glossary/service-panel) (usually 100, 150, or 200 amps). Before adding a heavy continuous load like an EV charger, an electrician runs this calculation (the method lives in Article 220 of the National Electrical Code) to confirm there's headroom. If the existing load already uses most of the panel's capacity, you either need a smaller or load-managed charger or a panel/service upgrade. It's the step that decides whether an EV charger is a simple add or a much larger job.