Charging a nikon digital camera with the USB cable?

Hi
is charging my Nikon digital camera via the computer (USB cable) just as efficient as charging it with the mains cable?
or is it just slower

Charging your camera through a USB cable will be slower but does have its advantages. Over charging a battery is very bad. If you plug it up to the wall the more voltage can cause your battery to not last as long as it would with the USB. Now if you had a smart charger that would not be the problem. But assuming you don't USB is slower but safer.

If its a DSLR you really should charge it via the mains… Even if it's a compact - if the option of charging via the mains is available then use it, - I only charge equipment via USB when there isn't any alternative.

Doesn't the instruction booklet advise you on this?

Depends on the USB port and the internal battery charger in the camera.

The Nikon EH-69P USB power adapter that probably came with your camera can supply a 550mA charge current, while a USB-3 port on your computer - if you have one (newer computers may have one), can supply up to 950mA charge current.

Older computers with USB-2 ports range from 200-500mA, so if you have a USB-2 port, it may take longer; especially if it only supplies 200mA. And if you are sharing the port with other devices, it may take a really long time. So if you are using USB-2 for charging, dedicate that port to the camera.

So, using a USB-3 port is no guarantee the charge will be faster as the charger may not need/be able to use the extra charge current available with the USB-3 port. But at least it will be as fast as using the Nikon adapter. A USB-2 port… It will probably take longer.

It is slower. I use the charger for my Coolpix s 3300.