Battery usage depends on the chipset, with newer chipsets using less power. For example, I've had a misbehaving app leave on the GPS on my Nexus 5X, and I still got battery life of about 8 hours. That's not good battery life, but the power consumption was low enough that I didn't notice the phone heating up in my pocket, and I was able to get through a day at work before it went into power saving mode.
My impression is that the real killer with the map app is screen usage. If you leave the map in the foreground, it will leave the screen on, and that drains power like crazy. Even if you hit the power button to turn the screen off, it will keep updating what it's showing on the screen, and that will continue to eat a lot of power. You can save a lot of power by going back to the home screen or another app, which lets you get voice prompts but avoids the power drain from the screen rendering.