They plug in using the factory harness. There was a option to get the extra H.I.D. adaper which would have to be spliced into the harness, but would give a more H.I.D. headlight shine. I was cheap and just got the lights. The lights are nice and bright as is. I did however splice in 2 relays so the halo turns off when the headlights are on as you can't see the halos with the lights on anyways. I don't know if these use more/less amps then the factory lights