Is it more energy efficient to charge a phone/tablet using a desktop/laptop while your computer is being used vs using the charger?
I was just thinking if you are on your computer anyway would it just use some of the excess electricity that your computer would have wasted or would it be worse than charging your phone from a charger while using your laptop separately.
It is a little bit more efficient, because your PCs Power Supply is not very efficient when you dont use much power. By using it more of it, it becomes more efficient, peaking somewhere at 50%.
But: we are talking about very little differences here and only for Desktop PCs. When you use a Laptop, you Powersupply is way less powerful, so you use more of it by just using the Laptop. So in that case, i would rather use the charger. To be perfectly honest with you: All that is not realy worth thinking about. Its like opening your Fridge for only 6 Secounds instead of 8. Yes, its saves power, but there are petter ways to do so. Doing only 1 kilometer less with your electric car ist about the same as charging your phone 10 times.