Because of the &quot;high voltage.&quot;<p>AC versus DC is not all that important by itself. What&#x27;s important is transmitting electricity at high voltage.<p>Transmission losses come from the amount of current you pass through a conductor. More current equals more power lost to the resistance of the conductor.<p>Delivered electric power is equal to voltage multiplied by current. Higher voltage means lower current for the same amount of delivered power, which means lower transmission losses.<p>The AC versus DC thing comes in because you need lower voltages for practical applications (it&#x27;s hard to run a light bulb off 100kV) and that means you need to transform between different voltages. Transforming AC between different voltages is pretty easy: an AC transformer is basically just a pair of coils with a metal core, easily built with 19th-century technology. Transforming DC is much harder and requires much more advanced technology.<p>For the 19th-century battle, this meant that AC was the only one that could be transmitted at extremely high voltages. DC was limited to serving very small areas because it had to be transmitted at the same voltages which would be used at the destinations.<p>Today, that difference goes away, so the advantages and disadvantages are all about much smaller secondary effects instead.