The A6210 did an amazing job at locating other nearby WIFI access points. It's high sensitivity and ability to pull-in weak WIFI signals was excellent. The unit did not seem to deplete my laptop's battery any faster than the built-in WIFI does.
I tested the Netgear model A6210-100PAS, AC1200 WIFI, USB 3.0, high-gain, dual-band adapter; This external WIFI adapter is intended to upgrade your existing laptop or desktop to use the latest and fastest WIFI-AC standards; The new WIFI-AC standard supersedes WIFI-N.
I would occasionally receive warning messages that no Internet connection was available; If I hit the reload icon in my browser, the requested page would then load correctly; Perhaps the AC6210 goes into sleep mode, when idle, to conserve the laptop's battery