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Service Calculations for Dwellings

Dwight E. Beasley, PE

Course Outline

This one hour course is an introduction to the Optional Method to calculate the electrical service to dwellings. The course material covers the calculation for single and multi-unit dwellings. The course materials are based on the 2008 National Electrical Code (NEC) ®.

This course includes a multiple choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

The purpose of this short course is to provide a methodology in calculating the electrical service to dwelling units as per the NEC. At the conclusion of the course, the student will be able to apply the learned material in calculating feeder and service sizes.

Intended Audience

The course is intended for electrical engineers involved in designing residential electrical distribution systems. The systems are for single family houses or multi-family apartments and condos.

Benefit to Attendees

The attendee will become more familiar with the process in designing residential services. Techniques in how to provide the minimum service size that meets code will also be covered in this course.

Course Introduction

The course includes all the necessary information to do the following:

In addition, the attendee needs to obtain the NEC 2008 book to aid in the study of the material. A copy is available at  It is recommended by the author for the user to become familiar with Articles 220, 230, and 240 of the National Electrical Code® in order to fully integrate the provided material.

Course Content

In this lesson, you are required to download and study the following course content in PDF format:

Service Calculations for Dwellings

Please click on the above underlined hypertext to view, download or print the document for your study. Because of the large file size, we recommend that you first save the file to your computer by right clicking the mouse and choosing "Save Target As ...", and then open the file in Adobe Acrobat Reader. If you still experience any difficulty in downloading or opening this file, you may need to close some applications or reboot your computer to free up some memory.

Course Summary

This course provides the criteria necessary in determining the minimum service and feeder sizes based upon using the NEC Optional Calculation.  It covers the sizing of services that meet the conditions stated in order to use the Optional Calculation.


Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

Take a Quiz

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.