Use the phone companion from Windows 10 with my Android phone to listen to my music from my laptop?

[WPCentral Question]

I have a Android - ZTE Maven with a small data pkg and just wondered if setting up the Phone Companion from Windows 10 is worth it or will it eat up my data by turning on the app and listening to the music stored on my laptop.....or should I just stick with listening to the limited music stored on my external microSD? I'm guessing that if I'm on WiFi I could use it, but while I'm driving (car w/o WiFi) it would only work off a data pkg.???

I can't seem to find any info online about this anywhere.