For most homes, a 200-amp panel is sufficient. However, larger homes or those with unique power needs (e. Hiring a licensed electrician is essential when assessing and upgrading your panel. From residential 100-amp panels to massive 600 amp main distribution panels in commercial facilities, this comprehensive guide will help you understand distribution board types, sizing calculations, and installation requirements to make informed decisions about your electrical infrastructure. Panelboards supplied by a 4-wire, delta-connected, three-phase (high-leg) system must have. No part of this book may be reproduced or distributed in any form or by any means without prior written permission from Avista Corporation. This publication supersedes all previous editions. Requirements for service are subject to change without notice, including in-between publications. Please. The National Electrical Code (NEC) provides comprehensive safety standards for electrical installations, including requirements for electrical panels (main service panels and subpanels or breaker box). NEC Article 408 covers switchboards, switchgear, and Panelboards installation and applications. Multiply the total square footage by 3 VA per square foot per NEC Table 220.