When using a Portable Generator it is critical to have properly sized and grounded extension cords. Portable Generators come with a variety of Outlet configurations depending on the Wattage rating and Amperage (Amp) output of the Generator.
At the minimum, all usually have at least one or two 15amp rated electrical outlets – similar to the type that you find on the wall in your home or office. The next configuration is one or two 20amp rated outlets (the type your Refrigerator or Freezer or Air Conditioner might use) sometimes combined with either a 20amp or 30amp Twist-Lock outlet (used to connect to a multi-outlet box or Utility/Generator Power Transfer Switch.) The take-away is that each Generator has its’ own outlet configuration and requires some thought as to how to connect it to the equipment in your home or office.
The important thing to remember when selecting the proper size extension cord for your Generator is that the higher the Amp output of the outlet, the thicker the copper wire in the extension cord needs to be to safely carry the electricity in to your home. When selecting the correct gauge for an extension cord, the lower the gauge number the thicker the wire and the greater the capacity of the wire. A 12 gauge extension cord can handle a greater capacity (Amp load) than a 14 gauge extension cord. A 14 gauge extension cord more than a 16 gauge extension cord.
A 12 gauge grounded (three prong) extension cord can safely carry a 15 amp load up to 100 feet. 15amps is the most common circuit capacity of the electrical outlets in your home. A 14 gauge grounded extension cord can only carry a 13 amp load the same 100 feet.
Higher amperage ratings may require 10 gauge cords depending on the distance. No Residential Home application should use an extension cord of more than 150’ without Professional guidance from a Licensed Electrician.
Every Underwriter Laboratories (UL Listed) extension cord is clearly marked with the gauge, maximum number of Watts and Amps it is safely capable of carrying. NEVER EXCEED THE MARKED RATINGS OF THE EXTENSION CORD!
Try to use the shortest length extension cord possible to improve efficiency of the transmission of electricity from the Generator to the device to be powered.
If the generator has a 20 amp or a 30 amp Twist-Lock connector, this requires a special Generator Power Cord. These cords will usually have the Twist-Lock connector for the Generator side and a multi-outlet box containing one to four 15amp or 20amp outlets on the other side. These special generator cords are usually 10 gauge or larger, depending on the length. (Remember, larger wire has a lower gauge number.) From this multi-outlet box, you can plug in standard extension cords of varying lengths to reach the equipment you want to power inside your home.
Any extension cord should be rated for Outdoor use because a Portable Generator will ALWAYS be outside AWAY from the house (to prevent carbon monoxide poisoning.) If you live in cold climate, I strongly suggest investing in the “Cold Rated” cords that stay flexible when the temperatures drop. Most Cold Rated cords come with the added benefit of heavy duty, resistant jackets that will hold up to rough garage floors, getting kicked around or walked over, and the elements.
If you need to convert a single outlet extension cord in to three outlets, use a specially made 12 gauge “pigtail” that has a 15amp heavy duty plug on one side and a heavy duty three outlet receptacle on the other side separated by a short length of heavy duty extension cord. Standard three-to-one outlet adapters are made of plastic and may crack if stepped on as they are meant to be plugged in to a wall and NOT an extension cord.
Another nice feature to look for is cords that have an LED light in the outlet end to let you know that the cord is “energized” and “live” with electricity. Given the fact that the Generator my run out of fuel and stop or be off for maintenance, the LED light gives 100% Positive feedback regarding the status of the power to your equipment.
In the case of expensive electronics like a Flat Panel TV, the Set-top Box, Internet Router or a Computer, connect an Uninterruptible Power Supply (UPS) to a 12 gauge extension cord to the Generator. This provides added protection from surges and filters the power. See my article “Hurricane Tech – Uninterruptible Power Supplies”
Personally, I always use 12 gauge, heavy duty, winter rated, grounded extension cords for an added margin of safety in 10’, 25’, 50’ and 100’ lengths. By using a cord rated for the maximum 15amps, I am matching the rating of the Circuit Breaker on the Generator and I don’t have to worry about the extension cord failing. The Circuit Breaker on the Generator should trip before the cord fails. Since 15amps is the size of most household circuits, if I match the equipment I would normally plug in to a wall outlet to my 15amp Generator Circuit, everything is the same and therefore properly sized.
IMPORTANT SAFETY NOTE: Periodically feel the extension cords to see if they are cold, warm, or hot. If an extension cord is warm or hot, that means that you are exceeding the carrying capacity of the extension cord and should immediately un-plug it from the Generator or Power Source (Utility Power.) Get a higher amp rated extension cord. FAILURE TO DO SO COULD RESULT IN RISK OF FIRE.
I have a 20 amp receptacle on my generator. I purchased a 25ft, 10/3 cord, with a 5-20p plug and a built in splitter for three 15amp female connections. I plan to use it as my main power cord from the generator to the house. It was advertised as a 20amp generator extension cord, but when I received the shipment, the packaging labeled it as a 15amp cord. Since it is 10 gauge wire (actual and per label) and has a 5-20p plug, am I okay to use it safely? By using it, will it somehow reduce my generator amp capacity to 15amps?
The first thing you should do is look for a UL – Underwriters Laboratory rating to make sure you have a high quality cord that has been properly tested for safety.
The reason for the 15amp rating is because the cord has three 15amp female connections on one end.
Since it is 10/3 cord, yes, 20amps at 25′ is not an issue for safety PROVIDED that the total draw of all of the devices you have connected to the three female outlets at the same time is LESS THAN 20amps with each device drawing LESS THAN 15amps per outlet.
Thank you for your question,
Jason Palmer