Does The Length Of An Extension Cord Affect The Power (What You Need To Know)

The short answer to this question? Well, that’s a yes. The length of an extension cord does have an effect on the power - BUT, there are lots of ways that work to reduce this, and we will tell you everything that you need to know.

What are you waiting for? Read on to find out more info about all things extension cord related!

Does The Length Of An Extension Cord Affect The Power

Why Does This Happen?

It is true that long extension cords can cause pretty big drops in voltage in your appliances. Anything that shows resistance to the flow of electricity actually makes the voltage decrease.

The amount at which the voltage decreases and whether this decrease should be something to worry about is another matter. In fact, even a short wire will cause an insignificant voltage decrease. 

However, for practical purposes this is not something you need to usually think about. Even at full current rating, using an extension cord is very unlikely to give you a power voltage loss of more than 5%.

So, in practical terms this is the sort of decrease in voltage that you’d find when multiple appliances are turned on at the same time in a household, or if your neighbourhood switches on their Christmas lights all at the same time.

So, altogether this is a voltage drop that is not really that noticeable. It will not cause a power cut or destroy your appliance - as long as you use your extension cord when you need it and not be lazy about it.

What do we mean by being lazy with your extension cord? The problem is that lots of people won’t go to the effort of uncoiling the full length of an extension cord, and will then expect to get full power drawn from it. Yeah, this is a classic lazy human technique.

We’ve all been guilty of this renowned technique at some point. But, those few seconds it takes to uncoil your extension cord make all the difference to not only the function of your appliance, but the lifespan of the extension cord itself.

If you uncoil the extension cord every time you use it, it will be guaranteed to last you for that much longer.

Extension cords are valued for use in free air - and if you coil up a few dozen turns, the handful of watts dissipated in the cable will turn into an electric heater. What does this mean?

Well, good quality extension cords would have a thermal cut out which would prevent this, but you do need to devalue the power output of your extension if you plan on keeping it partly coiled up.

Not only that, but the cord could heat up and depending on the surface that it rests on this could be a fire hazard.

Does Size Matter?

Now, get your mind out of the gutter guys… but in this case, size really does matter. Well, length in particular matters here. 

This is because the current loses some voltage as it flows through the extension cord. This can have a knock on effect on the appliance or the multiple appliances that you are trying to power.

The important things here are: the length of the extension cord, the gauge of the wire and the current draw of what you are plugging into the cord. If you take all of these into consideration when purchasing your extension cord then you won’t go far wrong.

What Is Voltage Drop?

So, any resistance to the flow of electrical current causes a voltage drop and the spanner in the works here? All wires have resistance. Over short distances, the voltage drop is practically unnoticeable - but as distance increases so does the voltage drop. 

Voltage drop can be reduced to a certain extent by using heavier gauge wires, and the amount at which the voltage can drop over the length of an extension cord is an important thing to think about for safe appliance use.


There is a growing concern that if voltage drop is too far below 110 volts, more current will flow in order to make up the difference. In turn, this can make wires heat up and then the appliances run hotter.

Just be careful with how many appliances you have on the go with your extension cord depending on how much wattage the extension cord can deal with.

Using Extension Cords

So, extension cords are actually pretty safe and won’t cause problematic voltage drops if they are used correctly. Light duty extension cords should be used for smaller appliances such as lamps and WiFi routers. 

The bottom line is that you do not need to use extension cords that are longer than necessary. Larger appliances will require heavier gauge wires, and appliance extension cords are made for this very purpose. 

A 6-foot appliance extension cord will not cause a problematic voltage drop if it meets the requirements of the device or devices plugged into it.

Appliances And Extension Cords

So, the best piece of advice we have for you is: do not use an extension cord for the sake of it. If you can plug an appliance in with the original plug and use it effectively then just do this.

Use an extension lead only if you have to, this is not just a convenience measure, and use the right kind of extension cord for the rated amount of current that the appliance uses.

Make sure to arrange your extension cord safely and never put it under any rugs or where they would be damaged. 

Extension cords can affect the power outage, but hopefully through this you can now see that there are lots of ways to reduce how much extension cords can affect the power. 

Our last words of wisdom to you are: use an extension cord if you need to, and make sure you use it in the right way. Do not under any circumstances be lazy.

I'm an environment and energy blogger who teaches outdoor and energy enthusiasts how to be better informed when it comes to purchasing or maintaining a generator, solar panel system, or anything else related to your energy needs.