>> GPS is also the biggest battery hog on the device.
Something is, but I find it very hard to believe it's the GPS itself. It's, after all, a completely passive system. What eats battery is transmissions and computation; with GPS, the first doesn't happen, and there isn't much of the second either.
I guess what happens is (on some phones; I've kept GPS always active on my Galaxy S4 and S7, and never noticed a difference) having GPS active makes various services run in your system, which may or may not be poorly written / poorly integrated with phone's power management.
On modern phones, you are unlikely to observe any power savings by turning off GPS or "location services".
The GPS is only going to use significant battery power when it is acquiring or actively calculating fixes. No device or OS vendor would ship software that burns the GPS at all times--your device's battery wouldn't last more than a few hours.
The grandparent is totally incorrect about the GPS being the biggest battery hog on the device. Not even close, unless you are, 24 hours a day, navigating or running some other application that requires continuous (1 second duty cycle) GPS fixes. Even then, your backlight is likely consuming an order of magnitude more power.
While GPS is not a huge power hog in comparison to other things on phones, the cost of listening on radio is not negligible, which is why most low-power radio protocols put a lot of emphasis on only listening in certain time windows.
Something is, but I find it very hard to believe it's the GPS itself. It's, after all, a completely passive system. What eats battery is transmissions and computation; with GPS, the first doesn't happen, and there isn't much of the second either.
I guess what happens is (on some phones; I've kept GPS always active on my Galaxy S4 and S7, and never noticed a difference) having GPS active makes various services run in your system, which may or may not be poorly written / poorly integrated with phone's power management.