Do power adapters save us energy consumption?

Question

Hi.

If I am using my laptop via the mains adapter - am I using up all 220V? Or is some of that being saved if my power adapter is only using ~20V?

Another example: If I am using LED lamp that uses 6V DC adapter to run via mains - am I using up the entire 220V or am I only consuming a fraction?

Bottom line: Am I saving £ on my electricity bill when using adaptors?

Answer 1

They waste a little actually, but are needed for modern electronics.



The 220 is just there, you do not consume it. What you use is the current, or more accurately power, measured in watts, or metered by your electric meter in Kilo-Watt Hours.



Your power adapters will take what current from the mains, that they need to power the device they are connected to.



I will example my netbook adapter.

It draws about 10W running, 20W charging, 30W running and charging. The label states it is rated at 40W. I measured the current drawn by a small inverter from a 12V battery.

Answer 2

The power (W) rating and current (A) rating on the adapter is the MAXIMUM that the adapter can handle. If you exceed this amount by plugging in a different machine, you can fry the adapter. This is why some adapters have different plugs on the end. The computer will normally draw less than the maximum rated current.



And yes, you are correct, most lighting sources draw a fixed amount of power, such as the 500W-rated lamp. In other words, it will draw more power over an hour than your computer power supply due to the fact that the computer power supply will not often run at, or near, 500W.



Also, it makes no difference what voltage you are using - the power required remains the same. So 240W = 240V running at 1A. If you use a 12V inverter, the power will still be 240W, but the current will be 20A, plus a little bit more due to the heat created by inverters.



If you take a halogen lamp as an example - a 50W lamp will run at 0.2A if you use mains voltage. If you have a 12V, 50W lamp with a 12v transformer, it will run at 4A, but the power will still be 50W. And this can be seen because the light output is similar.

Answer 3

If you're using electricity, you're not saving on your electricity bill.



Power adaptors are not 100% efficient. They all waste a small amount of power in the form of heat and stray magnetic radiation. Modern switch mode adaptors are around 95% efficient.vv



An LED is close to 100% efficient in converting electricity into light. However, they need a current limiting resistor that can reduce the efficiency considerably. If you have an LED lamp with a forward voltage of 4.8v running off a 6v power supply, it's running at 78% efficiency. That's about the same as a fluorescent lamp that's constantly on (so called energy saving lamps use a lot more power to get them going) and about 3 times as efficient as a tungsten lamp.



An LED lamp that runs off the mains using a constant current power switched mode power supply could be around 90% efficient - but I haven't invented it yet.

Answer 4

Your electric bill is figured by the amount of current you are using not voltage. All devices are set up to run on a certain voltage to supply the current it needs ie: adapters. If your device needs 5 amps of current to work it will get it no matter how you supply. If a transformer is left plugged in it will draw a certain amount of current no mater if you use it or not So you are consuming electricity with all the adapters plugged in whether you are using them or not. That is why they are warm to the touch. Hope this helps.

Answer 5

conserving the environment is a socially very responsible thing to do. While we sit here, in our town homes, with ACs and Fans continuously switched on, there are villages,scores of villages where people have no electricity and water.



Recently I had gone to Gujarat on a trip, and I discovered one village where they had 24 hours power and water. And they used it in phases to conserve it. It was brilliant. Apparently the Gujarat Government innovated to get them 24 hours of supply of power and water, and its the only village in India to have that. I found a case study on them online - check it out .



http://www.slideshare.net/InnovationIndia/jyotigram-innovation-for-india-award-winner