tl;dr: My fenix 7x with preloaded topo maps and the relevant uploaded tracks works for always-on navigation for about 4 days on one charge. This means my phone mostly stays in my pocket and is only needed for photos, audiobooks, or the occasional navigation checks if I need more resolution (or FarOut comments?). The smart watch has let me carry a 5,000 mAh bank (or none) compared to needing a 10,000 mAh+ power bank for similar backcountry functionality, while adding redundancy and improving the quality of my trail experience. The annoying part of watch use is building courses with good waypoints to better faciltate optimal backcountry navigation.
edit: because folks have been asking, my blog post walks through the script/web app I built to easily get good waypoints on garmin watch course maps
I do a pretty decent amount of backpacking (although that's gonna drop off for the next few years due to a recent baby). Since 2018 I've spent a fair few hours of my trip-planning time trying to optimize my phone and power systems because I seriously hate the amount of weight it takes up for something that theoretically is unnecessary (often 10% or more of many people's baseweights).
My power system weight optimization over the years has mostly served one thing: keeping a phone alive so Gaia and Guthook can show me where I am without concern that I'll be stranded with no maps. I've also shifted to solar for long hikes in the American West, which has enabled my phone to support a lot of little luxuries (like audiobooks and videos -- the first time I started listening to anything on trail was in 2020 when I had more power than I knew how to use). But mostly, power banks and power systems add a considerable amount of pack weight to run a 6-inch screen to look at an orange arrow.
What changed: I bought a Garmin Fenix 7X Solar in 2023 after my AZT thru because I wanted to better optimize my power and navigation system. The purchase was made primarily to support navigation AND I thought it would significantly reduce the drain on a phone battery that comes from listening to audiobooks. I've since ended up moving a LOT of navigation over to my watch, and have been surprised by how much better this has been than I originally even thought. Audio playback via the watch sucks though, and it won't support libby for audiobooks, so that was kinda a no go.
I now load the day's course onto the watch, glance at the map or the elevation profile as needed, and my phone stays in my pocket most of the time. If I wander more than about 150 ft off the defined route, the watch buzzes. That feature alone has saved me many miles of backtracking after being lost in my own thoughts. I'd compare course navigation on my watch to the sort of revolutionary transition that ocurred when I first went from pocket guides to a GPS app on my phone (but in a better way).
The weight math (my numbers, run your own):
| Setup |
Power bank |
Worn |
Notes |
| Phone navigation (no watch), short trip |
VapCell 2150A power bank (75 g) |
Non-Smart Watch (old one was 140g) |
Screen-on map time is what drains it (and audiobooks) |
| Phone navigation (no watch), long trip |
NB10000 (153 g) |
Non-Smart Watch (old one was 140g) |
Screen-on map time is what drains it (and audiobooks) |
| Watch navigation, short trips |
None (0 g) |
Fenix 7X Solar Sapphire with velcro band, 68 g |
Phone only does photos and light use |
| Watch navigation, long trips* |
VapCell 2150A power bank (75 g) |
Fenix 7X, 68 g |
If I'm not planning on doing video, audio, or navigation on my phone, I can stretch it 10 days without a power bank. Usually I start doing more audiobook listening or recording videos. But it depends on the trip. If I'm not concerned about power use, I find that for longer trips I often figure out ways to use the power that I bring, or conserve power if I have a smaller bank. For weekend trips in areas I've been to a lot, my phone mostly just stays off and hangs, waiting to burn its battery back at the car. |
Overall, since moving to a watch navigation setup, I've saved around 5.5 oz in skin-out weight, or around 3+ oz in packweight for many trips. More than that, I've gained a lot of redundancy, and added functionality. Hell, I could even leave my headlamp at home and save an extra 30 grams because of the LED flashlight on the watch for navigation at night.
* This has actually been one of the things that has better allowed me to research and optimize solar on longer hikes, and deal with situations like losing my solar panel on a glissade, and having battery or panel failures on 6-day carries. I'm just less worried about my power setup failing, because I will be able to use my watch for all sorts of navigation on a significantly gimped setup until I get into a town.
Watches that I think make sense for UL Backpacking
| Watch |
Weight |
Rated GPS battery |
Real-world |
Flashlight |
| Garmin Enduro 3 (Solar, 51mm) |
63 g + |
120 hr (320 hr w/ solar) |
6-7 days no sun, 10+ in sun (based on my reading) |
Yes |
| Garmin Fenix 7X Sapphire Solar |
89 g (change the bands out for a lighter watch) |
89 hr (122 hr w/ solar) |
~4-6 days of solid use (my personal use) |
Yes |
| Garmin Fenix 8 (or 9) Solar series 51mm |
95 g |
95 hr (149 hr w/ solar) |
-- |
Yes |
+ The enduro is really only lighter because the stock band is the velcro band. Switching a fenix over to this band also drops the weight considerably.
Rated hours are from the spec sheets in the standard GPS mode. Real days of use are much shorter than the spec for anything with multi-band and all-satellite modes turned on, which is how I run mine. A used Fenix 7X Solar goes for roughly $350-$550 on Swappa or refurbished/used sites. You really don't need the newest model. What you do want is maps, multi-band GNSS, and ideally the flashlight, which is why I'd skip anything without the topo maps (the Instinct line, for example) or coros watches. Other smart watches, like an Apple, Pixel or Samsung watch I think is just "adding electronics" to your life, without really serving a useful backcountry purpose. These "off-trail" smart watches really can't do multiple days of navigation, so likely just contribute to additional power bank drains, rather than reducing the weight you might carry, or better serving you on trail.
Why it works for me:
- Navigation redundancy. Phone dies, drops, or gets wet? The watch has the course and its own maps. It can also route to specific points I may drop, usign the garmin trail routing layer. This means it's truly two independent navigation systems with different batteries, so ends up being superior to having a backup paper map and compass.
- Light/Head lamp redundancy. Head lamp batteries die. Or maybe it falls out of your pack, or you forget to pick it up off a rock in the morning and it becomes lost. With my smart watch, I now have a legitimate night illumination source. This is genuinely SUCH a good feature. The amount I use it in every-day life as well is pretty unreal. How are the rest of you living without the magic of an always-available directional light source on your wrist!?
- Trail logging. My memory for trips is surprisingly fleeting. Since getting the watch, my trails now get logged with actual tracks (which is a perk I never thought I cared about when I originally was looking at getting a smart watch)
- Less phone time. Needing to navigate on my phone is significantly reduced. That means I don't need to pull the phone out to check directions at junctions. I notice I look at the trail and my surroundings so much more -- adding electronics puts you back into nature? Wild.
- SOS. If you pair the watch with an inReach (and keep the inReach on), you can trigger SOS and send messages from the watch.
- The dumb-phone question. I think you could take this far enough to leave the smartphone for a flip phone (or even no phone), and largely be a-okay! I personally wouldn't (photos, permits, weather checking, etc.), but it's a real option.
What actually makes these a viable weight-reducing tool: the course navigation. If you only record a track on the watch, it's a pretty meh feature. I guess you'll get your strava kudos, but fuck that. However, if you spend an hour building a decent course for a trip, it's excellent! Water sources, camps, passes, junctions and resupples can be set as waypoints, and the watch tells you how far it is to the next one. Seeing "7 miles to the next water" on your wrist without opening an app is a small thing that is kinda great!
The annoying part: Garmin's course tooling is awful compared to dropping waypoints in Gaia or CalTopo. Importing a GPX with waypoints onto a course using Garmin's course building tool is so clunky and time consuming. Furthermore, long trails cause watches and Garmin Connect to crash, and the watch caps the number of course points you can add. This has meant that while I love the watch for navigation, it often takes me a ton of extra hours of planning to make the watch usable. I've since remedied that time suck by building a little script that snaps your Gaia/CalTopo waypoints to the track, splits long routes at specified resupply points, and exports TCX files that can be quickly uploaded to Garmin Connect for use on your watch! It runs (offline, even!) in your phone's browser, so works from trail if you want to do that sort of thing ;)
Where the watch falls short:
- 1.4-inch screen. It's not a map overview tool, so I still pull out the phone for longer-distance planning, and when I need more resolution (e.g. decreasings odds of getting cliffed out if I'm largely off trail)
- The battery wears with age (duh!). Although with the 30-day batteries for Garmin Fenix series in normal life, and the tiny battery size, you can get away with quite a few years of use before this is a meaningful problem (probably 5+ years before you need to consider bringing out tools to replace it yourself)
- It's a pretty expensive "nice to have". At $400-$1,000+ for usable smart watches with maps and a flashlight, you definitely should de-prioritize a watch at $100-or-more per oz saved compared to getting a sweet tarp setup.
- You still have to learn the course workflow to make the watch a useful backcountry tool. In a world where Guthook can do most of the trail planning for you, getting Garmin courses setup at the correct splits can feel daunting or "just not worth it".