Not just GPS, but it is constantly using data services, sending info and receiving info about other Wazers, traffic data, etc., and repeatedly checking for better routes while you drive. In general, Waze uses more power because it is doing significantly more work than any other GPS nav app. A 2amp or higher car charger is a necessity.
3D mode also uses more power than 2D.
Not sure I recommend the "refresh map" option because that clears all of your map cache first and then freshly downloads all map tiles again, thus causing more power consumption as you travel around. If you don't clear the map cache, you may not need to download those map tiles.