Incredible Battery Life

I’ve publicly praised Apple for its honesty in reporting battery life over the past couple of years, and the iPhone 4 gives me no reason to stop.

The 4 has an integrated 5.25Whr battery. That’s around 95% of the battery capacity of the HTC EVO 4G, despite having much lower power frequirements. It’s also a 16% increase over the 4.51Whr battery that was in the iPhone 3GS. This means at bare minimum, assuming the iPhone 4 doesn’t draw any more power than the 3GS, we should get 16% more battery life.

In reality, we get much more.

When Apple introduced the iPhone 3G it dropped battery life to a level that we’d been stuck at ever since. The 3GS improved battery life a bit through better CPU power efficiency but you still didn’t have enough juice to get through a day without charging.

The iPhone 4 changes all of that. The combination of a larger battery and a more power efficient SoC results in an incredible amount of battery life.

Our first test is a basic web browsing benchmark. We've scripted almost two dozen webpages to load, pause for 20 seconds, then forward on to the next page. None of the pages use any Flash. This process repeats until the battery is dead. Screen brightness on the iPhones was set to 50% and the screens remained on the whole time.

Battery life improved nearly 38% with the iPhone 4. It's clear that while the A4 improved performance, the real improvement was in battery life. This test has enough idle time where good power management and low idle power can really impact the results. There's simply no other similar smartphone that can touch the 4's battery life.

We then repeated the same test over WiFi instead of 3G:

Apple claims the iPhone 4 will last for up to 10 hours over WiFi, we measured just under that at 9.96 hours. The improvement here is only 12.8%, which tells me that we're nearing the limit of how efficiently Apple can manage power in WiFi mode. There's a wall that we're quickly approaching with this current architecture.

To measure talk time we play MP3s on repeat into the mic of a phone and use it to call the phone being tested. The process continues until the test phone dies. In this case the screen is allowed to go to sleep, as it normally would be if you were talking on the phone:

Apple promised up to 7 hours of 3G talk time with the iPhone 4. We measured 7.47 hours. That's an increase of 54.9% over the iPhone 3GS. While in a phone call the majority of the A4 SoC is powered down, so the efficiency improvements here have to do with how much less power the A4 consumes while off and the new Skyworks 3G modem (the iPhone 3GS used an Infineon modem).

In our iOS 4 review we looked at the impact multitasking had on the iPhone 3GS' web browsing battery life. I ran our 3G web browsing test while playing music through Pandora in the background. I repeated the test with the iPhone 4 for today's article:

We actually see our largest battery life improvement in this test. With a 57.7% increase in battery life over the 3GS, the iPhone 4 is not only more efficient at idle workloads but also when the SoC is constantly busy. The A4 SoC is rumored to be built on a 45nm process compared to the 65nm SoC used in the 3GS. With a moderate increase in clock speed we should be seeing a lot of the power savings that a full node shrink brings to the table.

The battery life offered by the iPhone 4 is spectacular. My iPhone 3GS could hardly get through a full day of work while traveling, I'd always need to hunt for an outlet before heading into my dinner meeting. I'm about to take my first trip with the iPhone 4 but I get the feeling that I might finally be able to make it through dinner.

Early reports of 20 and 30 hours of battery life are simply exaggerated. They're only possible if you let the phone idle in your pocket for the majority of that time. In other words, if you don't use the phone it lasts for a long time. While that's a testament to the platform's incredible idle power, the real world usage is good enough to stand on its own. It's better than any iPhone or Android phone I've tested thus far.

Performance An iPhone with Bumpers


View All Comments

  • Mike Wadner - Saturday, July 03, 2010 - link

    Well then you're in pretty bad shape. Anyone who considers Microsoft not far behind Apple has their head up their F**KING ass. May be a nice review but I have doubts about their overall knowledge of whats going on out there. Reply
  • jorpoka - Wednesday, June 30, 2010 - link

    People seem to making a big deal about the increased ram in iPhone 4, but I think it was almost required.

    The graphics chip shares memory with the system (just like in previous models) so you have to consider the fact that the screen resolution has increased by 4. How is the system going to deal with the higher resolution grahpics... the 512 MB of ram.

    For now not every application on app store uses the updated resolution, but as more and more apps are updated for iOS 4 and the retina display i think the additional 256 MB ram benefit will decrease.
  • solipsism - Wednesday, June 30, 2010 - link

    The surprise wasn't that 512MB wasn't deemed needed, it was simply unexpected after the iPad with a higher resolution, faster processor and generally higher chance for more complex apps to run on the 8x larger display only being shipped with 256MB, like the 3GS, when 512MB was expected. On other words, if the iPad didn't get 512MB RAM, few expected the iPhone 4 being shipped just a couple month later to get it. Reply
  • John Sawyer - Thursday, July 01, 2010 - link

    Not higher resolution on the iPad, but more pixels (but we get your meaning). Reply
  • Snotling - Thursday, July 01, 2010 - link

    that's the point I'm trying to make since the iPad's release... it was not a planned product, it was ruched out just so they would not be assassinated by the press and the fanatics, my full conspiracy theory is on my blog:

    Now with the iPhone 4, we see what Apple was actually working on before rushing out the iPad and its a very good product. superior in every way to the iPad.
  • tkoyah - Sunday, July 04, 2010 - link

    Um, the iPad wasn't rushed. The iPad project actually pre-dated that of the iPhone. But when it became aparent that this would be the perfect interface for a Phone, the iPhone project began, and was given a higher priority.

    I expect this first iPad wasn't given more RAM: a) to keep the price-point under $500 b) because there was no pre-existing iPad software, so having less memory available wouldn't break any apps.
  • tipoo - Wednesday, June 30, 2010 - link

    The big deal is that the iPad, their tablet, has half the RAM of the phone they released shortly after. With a bigger screen and more pixels, people naturally would have expected the iPad to have the technological edge, but with only half the RAM of the iPhone that is not the case. Reply
  • AMDJunkie - Wednesday, June 30, 2010 - link

    Begins after this post. Reply
  • Zokudu - Wednesday, June 30, 2010 - link

    Wonderfully written article I love this line of high end smartphone articles you guys have been releasing. I love the quality of the writing at Anandtech.

    Just a few questions I have.
    Doesn't AT&T have a 5 year exclusivity deal for the iPhone meaning they would still have around 2 years remaining before an opposing carrier could offer the device?

    Also several of my friends with iPhones both 3G and 3GS constantly complained about AT&Ts coverage within New York and blamed the carrier. However several of them have gotten iPhone 4's and are reported fewer dropped calls if any at all. I have been using a Blackberry on AT&T's network for several years now and have had no issues with their coverage. Do you feel the dropped calls within hot spots such as New York should be blamed on the iPhone itself or the network?

    Also where do you feel that Windows Phone 7 fits into the future of smartphones. Do you envision it taking center stage against both iOS4 and Android or falling to the wayside such as webOS ended up doing?

    Once again thank you for the wonderful read and keep up the quality work.
  • JAS - Wednesday, June 30, 2010 - link

    AT&T recently upgraded its 3G network in New York City. So, the improved wireless connection experienced with the iPhone 4 might be coincidental.

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