Ethernet Cable and Battery Life

Not sure where the other post get his figures from but wireless uses the same if not more power than a Ethernet connection. With wireless you have 2 power draws. One is the wireless card itself, drawing power to send and receive the signal and another to convert that wirless signal into a Ethernet protocol for the computer to use.Not sure how a USB Ethernet card, dongle, could use more power than one built into the system.

Glad you got it figured out with the talk to the IT department.

It is not just the Ethernet cable. It is because there is something on your Mac that is constantly using the internet, reading and writing data to the internet.

That something could be malware, doubtful but possible, or you have something like Dropbox, iCloud or some other online system that is consatntly using the internet. Once you disconnect the network cable that stops so the battery run time goes up.

Wifi uses a LOT less power than Ethernet, using around 30mW

The Ethernet dongle can be using up to 2.5 watts, that's 2500mW.....native ethernet connections typically use a lot less, but the dongle to ethernet requires MORE power, ..hence more power out when using the AIR thru the ethernet dongle......

Wi-Fi in GENERAL consumes between 10 mW and 800 mW (transmitting full bandwidth); NATIVE Wired ethernet consumes 200mW to 1W

Wi-Fi uses 20% less power to transmit data at 50% the speed. On a bytes-per-milliwatt basis, Wi-Fi is about 60% less efficient than wired Ethernet.

The Ethernet to lightning dongle for the mac AIR loses some power in the transer and requires a bit more power from the Air, than say the ethernet port already IN the Macboo pro

When using ethernet, plug in your power, logically. When you on a chord for ethernet, most everyone is also on a chord for power also.

A native Ethernet chipset is different, and another story. A macbook Air doesnt have an ethernet port.

The USB or lightning dongle/adaptor is quite inefficient when it comes to power usage.

The USB to Ethernet or Lightning to Ethernet dongle requires power use and conversion itself, and contains a chipset which draws power.

A macbook AIR requires this dongle to Ethernet, which draws more power, and the conversion process itself draws power.

Wifi power output depends on SNR, and gain, ......output varies to acomplish communications. Its not fixed. 2.4Ghz and 5Ghz requires very little power in fact.

Heres a pic of the chipset inside a dongle, this stuff requires power of its own.