Electricity: Understanding How It Works: Assessing Your Electrical Service

If your home has two-wire (120-volt) electrical service or if you have a 60-amp three-wire service, consult a licensed electrician about converting the two-wire (120-volt) service to three-wire (120/240-volt) service or upgrading to at least 100 amps. While the minimum requirement for new homes is 100 amps, 200 amps is common in larger homes. Some may have 400-amp service. If you have doubts about the grounding system, consult a licensed electrician.

Got aluminum? Millions of homes were wired with inexpensive aluminum ( AL) cable because of high copper prices in the late 1960s and early 1970s. Such wiring can be unsafe if it's not properly installed and maintained. Aluminum wires are dull gray, not the dull orange characteristic of copper wires. Cables may be marked AL or Aluminum. To ensure your safety and the value of your home, hire an experienced electrical contractor to work on aluminum wiring systems, which require special techniques and wire connectors.

If your wiring is aluminum, replacement switches and receptacles, rated 20 amps or less, must be marked CO/ALR. Replacement devices rated 30 amps and more must be marked AL-CU. Replacement light fixtures and devices with pigtails, like dimmers, require special wire connectors.

Need more lights and outlets? As long as you don't exceed the capacity of your service panel, you can add new receptacles and fixtures by either extending an existing circuit or installing a new one. Before extending a circuit, check your circuit map to make sure the additional receptacles or fixtures will not overload the circuit. To install a new circuit, the service panel must have space for a new breaker. To add a new circuit, combine underused circuits, substitute half-size for full-size breakers (if your panel is listed for half size) or connect a sub-panel to the main panel. Contact a licensed electrician for this type of work.

Are you looking for home electrical items -- such as switches and fuse boxes -- or parts and accessories for ones you already have? Try our dedicated electrical supply pages here:

Brand Name Manufacturers

Typical Wattage Ratings

The wattage figures listed here are averages. Your appliance wattage ratings may vary significantly Always check the appliance nameplate ratings for the correct voltage wattage and amperage If the rating is given in amps multiply the amps by the volts to obtain the approximate wattage (use either 120 volts or 240 volts).
Appliance Watts

Air conditioner, central Air conditioner, room


Broiler, countertop

Clothes dryer

Clothes iron

Coffee maker



Fan, ceiling

Food processor

Frying pan


Furnace, gas forced-air

Garbage disposer

Hair dryer

Heater, portable

Microwave oven

Range, oven

Range, cook-top only


Saw, table

Saw, circular




Trash compactor

Vacuum cleaner

Washing machine

Water heater































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Recommended Reading

Electrical Wiring Residential: Based On The 2005 National Electric Code

Book Description:

The Fifteenth Edition of this trusted resource is completely updated to the 2005 National Electrical CodeĀ®, and provides aspiring electricians the necessary foundation for learning all aspects of house wiring in order to ?meet Code.? The most comprehensive book of its kind on the market, Electrical Wiring Residential walks readers, room by room, through the proper wiring of a typical new residence, and features a complete set of full size plans and specifications that shows how Code requirements are applied throughout actual installations. This book explains and follows the NEC using the metric system, and presents an ample quantity of electrical formulas that electricians need to know to be successful and competent on-the-job.

Topics include:


After buying the Black and Decker Home Wiring guide and finding conflicting information, I decided I needed a more thorough reference (but didn't want to have to decipher the NEC). After a bit of research, I decided to buy "Electrical Wiring Residential". Within the first hour of reading it, I had two major questions answered that the B&D book didn't even attempt to address. While I've only had it for a day, I'm already 100% more satisfied with it than I was with the B&D book. My advice: buy this guide instead of the less expensive ones if you plan on doing your own wiring and want it to be to code.

Update (6/26/2006): I've gotten through about 1/3 of the book now and continue to be impressed. The way the sections are organized makes it very easy to learn the code. I did go out and buy the NEC Residential Handbook (2005) so I could reference it as I read through this guide since some of the tables aren't reprinted (probably for copy right reasons). Even without the NEC, the book explains the codes and regulations very well. The more I read of this guide, the better it gets.

I have wired four new homes and remodeled one using the concepts in this guide. The homes ranged from 3200 to 5000 square feet in size. The 5000 sq/ft house used 400 amp service for the main panels. I am a do it yourself homeowner. I am a firmware engineer by trade so I don't wire for a living. This book was magnificent in helping me understand how to put the entire picture together for a large complicated home. These homes included security systems, phone systems, home audio systems, internet wiring, and of course power and lighting everywhere that I needed it. I learned so much from this guide and the way that it walks through each room in the house. I recommend following it all of the way through on your own house plans. What it lacks I was able to find by looking at homes being constructed in the area. Things like how high up do I put the outlets and switches comes to mind. The code changes every three years and so does this guide. I got most of my knowledge from the 1993 book. I used the 1996 and 1999 books on the later homes but the basics were already there. All code changes are very well covered in the latest edition and nothing is dropped from edition to edition that I know of. I am very impressed with Mullin's style and thought that I could show some of my gratitude back for the help that he gave me to do this over and over again. I have recommended this guide to many friends who have also wired their own homes. If I needed to I would buy it again but I have decided to live in one of my houses for a while. What I believe this guide has that others don't is a grasp of the whole picture. I was able to do the entire project each time with this guide. I installed the service conductors from the transformer to the house. I built up the main breaker panels and subpanels. I performed the load calculations to make sure that all circuits were properly balanced. I don't think that many of the other wiring books cover all of these things. You can perform the entire wiring of your residential home by yourself with the knowledge that you can glean from this guide and a few questions asked of your local inspectors and examining the work of electricians wiring in your area. Make sure that you follow the code and not the local electricians though because I don't know how some of them pass inspections with some of the work that they do. Good luck on your project.

This book is an excellent reference for anyone who is engaged in electrical work of any kind. This edition is updated with the latest National Electrical Code (NEC 2005).

What makes this guide so good is that it's written in clear, and simple language, full of helpful examples, techniques, tables, shortcuts, illustrations, quick calculation methods, and tips, allowing the do-it-yourselfer as well as the professional practitioner, to do their job right, taking into account all the "safety must". The book covers completely all requirements for over current protection, grounding and installation applied to all commonly used wiring methods for residential installations.

This edition is updated to the last revision of the NEC, which was released in 2005. As you probably know the NEC undergoes a rigorous review and revision process every 3 years by the National Fire Protection Association (NFPA). The National Electrical Code is an internationally accepted safety code for electrical and power wiring. It specifies the minimum provisions necessary for protecting people and property from hazards arising from the use of electricity and electrical equipment. Anyone involved in any phase of the electrical industry must be aware of how to use and apply the Code on the job.

The NEC is a Mandatory reference for anyone who is engaged in electrical work of any kind, and this guide is without any doubt a trusted resource for understanding and applying the Code. The book will be helpful for both professional and students.

Recommended Products

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surge protector: Multiple strip with phone, fax and coaxial cable protectors

Surge Protectors

Surge protectors are designed to protect sensitive electronic equipment, such as computers, televisions and stereos, from spikes and surges that occur on power, telephone and coaxial cable lines. The warranties for such equipment are often void if you fail to provide surge protection. Surges and spikes can be caused by utility switching operations, lightning strikes or motors and appliances in the home. Surge protectors absorb and dissipate excess energy, often sacrificing themselves to protect the equipment. Replace protectors that are worn out.

Surge protectors are required to be plugged into grounded outlets to operate properly and dissipate excess energy. All connected equipment must be plugged directly into the protector. Extension cords, adapters or other electrical connections aren't advisable. Whole-house surge protectors are also available.

Surge suppressors carry a rating for a unit of electrical energy called a joule. Higher joule ratings mean surge protection devices will absorb more damaging energy from over voltage surge conditions.

Simple point-of use surge protector and a Point-of-use with telephone protector

(Left) Simple point-of use surge protector and (Right) Point-of-use with telephone protector.

Last modified: Friday, 2013-04-26 10:02 PST