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Do Extension Cords Waste Electricity?

Out of necessity, many people use extension cords around their home. Maybe you’re using the cord to plug in a refrigerator that needs to be out in the garage, or to plug in a lamp that’s located far from an electrical outlet.

Electrical extension cords are helpful, but are they also wasteful? Specifically, does using an extension cord waste electricity? Let’s consider the question in detail.

Do extension cords waste electricity when nothing is plugged into them?

Imagine a scenario. You have an outlet, and you plug an extension cord into it.  The cord snakes across your garage or basement, but nothing is plugged into the other end. Is this wasteful?

In most cases, the answer is no.  Unless something is plugged into an extension cord, there is no circuit present. Electricity isn’t flowing through the cord, and it won’t waste any power.

The exception is if your extension cord has a bank of switches at the end, or has a circuit breaker. These may consume a small amount of power and the cord is plugged in, even if nothing is plugged into the actual outlets. If your cord has one of these, it’s likely best to unplug it from the wall when you’re not using it, although the actual “vampire power” losses are likely small (see more below).

From a safety perspective, it’s also a good idea to unplug unused extension cords. If your room floods , the water on the ground can get into the end of the cord, causing a short. While a cord is plugged into the wall but has nothing plugged into it usually won’t consume power, it’s still a good idea to unplug unused cords.

Will plugging an appliance into an extension cord waste power?

The short answer is yes. Plugging an appliance into an extension cord will use more power than if the appliance was plugged directly into the wall.

The more detailed answer, though, is that it depends on the size of the appliance and also the details of the extension cord.  Extension cords waste a small amount of power because they create resistance to the flow of electricity. This consumes power without doing work, which is wasteful. The power is lost through heat.

The more current that’s flowing through the extension cord, and the smaller the cord is, the more power you will waste through heating. For that reason, and for safety reasons as well, it’s important to size your extension cord appropriately for the appliance you’re plugging in.  Make sure to use a cord that’s rated for more current than your appliance uses. For example, if your appliance uses 5 A, you’ll want a 10 or 20 amp cord to be safe. Thicker cords, and shorter cords, will result in less waste of power.

Should Extension Cords Get Hot While You’re Using Them?

It’s also important to note that your extension cord should not get physically hot while you’re using it. If you touch the cord and it’s hot, that’s a sure sign that you’ve overloaded it. That’s a safety concern. Either get a shorter cord, a thicker one, or plug in a smaller appliance. Check, too, to make sure that your cord isn’t damaged. If it’s damaged, discard it.

In general, if you want your extension cord to waste less electricity, go for a thicker cord, a shorter cord, or a lower power appliance. Using a thinner cord, a longer cord or a higher power appliance will result in more electricity wasted in the extension cord. 

How much power will an extension cord actually waste?

While it’s important to be mindful of our energy use, it’s also important to put things in perspective. As long as you’ve sized your extension cord appropriately for your appliance, and you’re not running it an excessive distance of hundreds of feet, the power loss will be negligible.

Electrical enthusiasts at Stackexchange once attempted to calculate the cost of using an extension cord. They determined that even for a bigger load like a refrigerator, the cost is fractions of pennies per hour. If you want to save money, focus your efforts on buying more sustainable appliances that draw a smaller load–as long as it’s sized appropriately, your extension cord shouldn’t cost you much of anything at all.

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