The Garmin Instinct Solar, harnessing the power of the sun

The Garmin Instinct Solar, harnessing the power of the sun

Abi Amstrong takes a look at the Garmin Instinct Solar watch. Garmin says the “Instinct is a GPS smartwatch built to break convention, conquer the elements and endure longer.” But that’s not all, it also takes “battery life to a new level by harnessing the power of the sun.” Read on and see what Abi thinks.

What is the Instinct Solar?

The Garmin Instinct watch is a smartwatch aimed at the more casual user rather than serious athletes but has a range of functions to suit all abilities. It will measure all-day heart rate, sleeping patterns, stress levels and activity levels even if you forget to record them. And you rarely need to charge it. It also can measure the number of repetitions when you do a strength workout, measure your blood oxygen levels, your stress levels and the amount of rest, and you can even calculate the area of a room or garden, and use it like a contactless card. As with all the Garmin devices it can relay text messages and notify you when you have a phone call.

Garmin Instinct Solar
What’s in the box?

Heart rate recording

I normally use a heart rate chest strap when I’m riding or running to ensure I’ve made sufficient effort or not pushed too hard, and so that I can judge my recovery afterwards.  The possibility of getting an accurate heart rate record without having to use a chest strap was appealing, so I double-recorded several activities with the Instinct Solar on my wrist and a heart rate chest strap connected to another Garmin device (the Edge 830 for bike rides, and the Forerunner 735XT for other activities).  Then I matched all the data and compared the heart rates from each device.

I found that the Instinct Solar was fairly accurate when I was making an effort riding uphill and less accurate when mountain-biking downhill. On the flat or uphill the difference was about 1 beat higher on the Instinct. However riding downhill the Instinct averaged five bpm higher than the chest strap, and even as much as 18-20 bpm on a couple of rides. The reason for this is the way that the wrist-based monitor calculates your heart rate – it measures blood volume. This can be affected by how tight the watch strap is and how tightly you might be gripping the handlebars.

Recording non-cycling workouts

This was more apparent when I was doing a kettlebell workout. Whenever I lifted the kettlebell with my left hand (the watch was on my left wrist), my heart rate was about 20 beats higher than the chest strap. The difference was negligible for running, although the fit of the watch is important here – too tight and it will record a higher heart rate, too loose and it won’t record properly.  The Instinct seems pretty good for day-to-day gentle activities, but if you are doing a more strenuous workout and want to get a more precise record of your effort, heart rate zones and calorie expenditure, then it’s better to use it with a chest strap.

Garmin Instinct Solar
The Instinct Solar has it’s own dedicated charger

Garmin Instinct Solar comparison charts

The elevation is shown as green area – this is important because the Garmin Instinct optical heart rate sensor (red line) can be seen to record similar heart rates as the chest strap (blue line) on the uphill sections, and often (but not always) gives a higher heart rate on the downhill sections.

In the first chart (1’10” activity length), there is a drop out shortly after an elevated reading. On the next hill, the Instinct optical heart rate was lower than the chest strap. At the end of the session on a descent, the Instinct showed higher heart rate than the chest strap as I must have been gripping the handlebars.

The next chart is a one hour extract from a much longer ride. It shows a long uphill section where the Instinct records higher heart rate, and this continues onto the descent. It’s possible that I was gripping the handlebars tightly on the climb as well as the descent.

The third chart is a two and a quarter hour activity with two climbs and two descents. Both heart rate records are similar on the climbs but the Instinct is higher on both descents. The Instinct drops out briefly on the second descent.

Move IQ

Move IQ is a neat function that makes a note of activities that you might have forgotten to record. These notes don’t contain any other information and you can’t rename them, only delete them. This function is useful for interpreting your day-to-day heart rate data or body battery data without having to press record every time you move. 

How does the Instinct Solar battery work?

The solar panels sit around the perimeter of the watch face and I rarely needed to charge the watch as long as I exposed it to daylight and didn’t cover it up with a sleeve. When it reaches about 50% battery power it offered me the option of switching to battery saver mode even though it said I still had another 11 days or so battery life!  Note that if you have the oximeter on during sleeping hours this drains the battery much more quickly.  Also, note that the optical heart rate monitor will use more battery power on darker or tattooed skin.

Sleep, breathing, stress recording and body battery

As with other Garmin watches this one can record heart rate while sleeping and produce a record of how long and how well you slept. I found this depressing – it continually berated me for going to bed too late, waking up too much in the night and for not getting enough sleep. It gave me better sleep scores when I didn’t do an evening bike ride or when I hadn’t drunk any wine, presumably because both these activities increased my heart rate for a few hours afterwards and prevented restful sleep. Eventually, I figured out that by changing my desired bedtime to an hour later I could avoid the feedback about going to bed late!

The oximeter function measures blood oxygen levels and can be used to indicate whether you suffer from sleep apnoea as it takes readings at intervals while you’re asleep and includes the data in the sleep widget in Garmin Connect. I compared a few daytime readings with a separate oximeter that clips onto a finger and found that the Garmin Instinct was on average five percentage points lower. Despite this, it could still be useful for looking at changes in blood oxygen levels but is not intended for medical purposes. 

The stress measure, based on your heart rate variation when you are not recording an activity, was useful. I could see the times of day when my stress levels were higher and how this impacted on body battery. The body battery takes into account sleep, rest, activities and stress, and it seemed a good reflection of how I was feeling. It’s a reminder of the importance of balancing activity and rest.  

Garmin Instinct Solar
These are the sensors that the Instinct Solar uses to record your blood flow


There is also a circular panel in the top right-hand corner of the screen that displays various metrics according to whichever function you’re using – the day and date on the watch function, or your heart rate when you’re recording an activity. While this is useful it takes up a lot of space and other data, text messages or notifications have less room to display making them harder to read. 


The comprehensiveness of the Garmin Instinct means that there’s a temptation to record absolutely everything you do. Which can keep you motivated and on track to achieve your goals, but you could easily become fixated on sleep quality or recording every step you take. It is a useful tool but has its limitations. So if you want to know how much cake you can eat after a workout then I recommend using it with a chest strap for those activities!

Photo shows hiking mode with heart rate in the circular panel and the darker solar panels around the displays.


Check out the Garmin Instinct Solar.

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