GPS & battery life

I often either walk or ride my bike with my GPS only Series 4 Apple Watch and it does not adversely affect my Apple Watch battery. I do not intentionally turn on nor turn off GPS. I just start the outdoor walk activity or the bike ride activity.

I do charge my Apple Watch while I sleep. The Apple Watch is rated for 18 hours of typical usage, and exercise activity is considered part of normal activity.

As I understand it, the FitBit lasts more than a day on a single charge. The Apple Watch really needs to be charged each night. A brand new Apple Watch might last 2 days, but that would be pushing it, and over time it would loose its battery capacity and you would be charging each night.

The coy part is that, Apple does not know if you are going to get a cellular and then spend 8 hours making phone calls away from your iPhone, or run an Iron Man marathon, or even just a 26 mile marathon at average person speeds, or hike for the entire day away from your iPhone, or you are going to play music stored on your Apple Watch via Bluetooth headphones, or consume even more power streaming music over the cellular connection for hours on end, etc... Or if you are going to mostly sit around the house or office, and get some moderate exercise in each day.

It really depends on how you use your Apple Watch.

Note: My Apple Watch is 2 generations old (about 2 1/4 years old). It is near the end of the day, and I have 56% battery life left. I have mostly been working at my home desk (no one is going into work at the moment), and I did ride my bike for an hour this afternoon, tracking my ride.

I do not play music, I refused 2 phone calls that T-Mobile said were most likely SPAM, and my Sister send 2 iMessage messages.

My Alarmed app has send me alerts for about a dozen things which rang on my Apple Watch.

56% remaining on the battery. I'll go to bed in about 2 hours and put the Apple Watch on the charger.

If I did not charge my Apple Watch each night, I would most likely run out of power at about 30+ hours. But I always charge it over night.

NOTE: As mentioned above, I do not put a lot of load on my Apple Watch. It is not cellular and 99% of the time it can use Low Energy Bluetooth with my iPhone, and let the iPhone do the heavy lifting for network communications. I do not listen to music on my Apple Watch, I rarely use it as a telephone (maybe about once every 2 weeks I'll answer a phone call on my Apple Watch). The most I do is the about 1 hour exercise I get each day.

Apple rates the battery for 18 hours. That is conservative, because batteries degrade over time, and they want the battery to basically last a day. Also they factor in that the user might be using the Apple Watch as a phone, and playing music on it, as well as exercise.

Again, if you are concerned about battery life, then if you get an Apple Watch, you should just plan on charging it everyday.

While I like my Apple Watch, and find it a very valuable addition to my tech toys, and I would replace it immediately if my current Series 4 stopped working, I also know that what makes me happy may not be the same as other people.

If you are going to switch from the FitBit to an Apple Watch, do it for reasons besides battery life.

My initial reason for "Justifying" the Apple Watch was the ECG and Fall Detection. After I got the Apple Watch, I rarely take an ECG and I've disabled Fall Detection because of too many False Positive events. But along the way I found all the other features I love about the Apple Watch for me. All my iPhone alerts and alarms appear on my wrist. No more taking my iPhone out of my pocket to see why it is beeping at me. I can answer the phone on my wrist. I can send and receive iMessages on my wrist (mostly short messages between my Wife and I). And speaking of iMessage, since my Wife almost never carries her iPhone with her, having iMessage on her wrist means I can actually use it with her. Having the weather on my wrist is maybe the thing I look at the most when I raise my wrist to look at my Apple Watch. And while I'm not anal about exercise and standing, I do find I pay more attention now that my Apple Watch monitors that sort of thing. Oh, and I like the Covid-19 hand washing timer and reminder when I come home. There are other features I find useful, but the above are my most used.

It depends on a variety of factors. Nobody here could tell you.

On my watch it's about 3 to 5 percent per hour if there's nothing else on the watch running.

Would have your iPhone with you, or would the Apple Watch be spending battery power to keep searching for your iPhone via Bluetooth or WiFi

That figure I quoted was with leaving my phone at home,I never take my phone with me.