How much battery does GPS tracking use on an iPhone?

The honest ranking

For a phone recording a route on a full-day walk, the power budget in rough order of size looks like this:

1. The display. It is the single biggest consumer on any modern phone, and it is entirely under your control — every time you wake the screen to check distance, you spend more than several minutes of satellite reception.
2. The cellular radio, especially in marginal coverage. A phone that can nearly reach a tower will transmit at maximum power trying to hold on. This is worse than no coverage at all.
3. The camera, while it is running. Video capture uses the sensor, the encoder and the display at once and is genuinely expensive — briefly.
4. The GNSS receiver itself, running continuously.
5. Everything else — sensors, background app refresh, notifications.

This ordering is why two people on the same hike with the same phone and the same app can end the day at very different battery levels. The difference is behaviour, not software.

Why continuous recording is cheaper than it sounds

A tracking app asks iOS for a stream of location updates and iOS decides how to service that request efficiently. The receiver does not run flat out at all times; it duty-cycles, and the system fuses satellite data with the motion sensors, which are dramatically cheaper to run. Between fixes, short stretches of movement can be estimated from the accelerometer and gyroscope rather than from the sky. This is why a phone recording all day does not behave like a phone running turn-by-turn navigation with the screen on.

It is also why a tracker that keeps working with the screen off is not just a convenience feature. TrailCam keeps recording with the screen off or while you are in another app, which means the correct way to use it — start the recording, put the phone away, stop looking at it — is also the cheapest way to use it.

What to actually change

• Turn on airplane mode when you know you are out of coverage. Location keeps working; the fruitless network search stops. This is usually the single largest saving available.
• Stop checking the screen. Voice announcements exist precisely so the phone can stay in a pocket — TrailCam can speak distance and pace as you go, and calls out interval sets aloud, in your language.
• Lower screen brightness, or let auto-brightness do it. Bright sun pushes the display to maximum, which is the most expensive state it has.
• Use Low Power Mode. It reduces background activity and display refresh. Foreground location recording continues.
• Keep the phone warm. Lithium cells lose usable capacity in the cold and can appear to drop very fast below freezing; an inside pocket rather than an outside one makes a visible difference, and some of that apparent loss returns when the phone warms up.
• Record video deliberately rather than continuously. Clips are cheap individually and expensive in aggregate.

On battery capacity and expectations

A phone several years old with a degraded cell will not match a new one, and no app setting closes that gap. iOS reports maximum capacity as a percentage of the original in the battery settings; if that number is well down, plan for a power bank on long days rather than chasing app settings. Cold weather compounds this: a cell at 80 per cent of its original capacity in freezing conditions can behave much worse than either factor alone would suggest.

For a full day out, a small power bank and a short cable is the answer that always works, and it costs less than any of the tuning above costs in inconvenience.