As consumers continue to use smartphones more frequently and for more power hungry tasks, battery life is a key focus for smartphone manufacturers. Apple's (AAPL 0.64%) iPhone 5s, however, is notably lagging behind the battery life many of its peers boast. Even the older Samsung Galaxy S4 outperforms the iPhone 5s on most battery life tests. Even worse, Apple still may only make modest improvements to iPhone battery life with the iPhone 6, according to a new report from G4Games.

Can Apple pull it off?
Citing various media reports in China, G4Games says that a new rumor points to a battery life of anywhere between 1,800-1,900 mAh for the 4.7-inch iPhone 6 and around 2,500 mAh for the phablet-like 5.5-inch iPhone 6.

MacRumors renderings, by Ferry Passchier, of the alleged 4.7-inch and 5.7-inch sixth generation iPhone lineup. Photo used with permission.

Considering the 1,570 mAh battery that powers the iPhone 5s and 5c, the improved power for the iPhone 6 may sound like a satisfactory jump at first. After all, that's about an 18% boost to battery power for the smaller iPhone 6 and a 60% jump for Apple's rumored phablet.

But lighting up those bigger screens is a draining task. As G4Games notes, the 5.5-inch LG G3 boasts a 3,000 mAh battery. And Samsung's 5.7-inch Galaxy note sports a 3,200 mAh battery.

Still, there is a chance that Apple's battery life for these larger iPhones could break-even or even exceed most competition. Fortunately, battery life isn't all about battery power. It's also about energy conservation. In Apple's seemingly relentless quest to make its devices thinner and sleeker, you can bet energy conservation is a key focus for the company. As The Motley Fool semiconductor industry expert Ashraf Eassa says, "If you can't get more power, use less!"

The quest for battery conservation mostly comes in two forms: (1) semiconductor innovation and (2) improved power management from the operating system. Apple is known on both fronts to be quite productive. In OS X, for instance, Apple often sets the standard on power management. In iOS, Apple's in-house and Arm-licensed system on a chip, or SoC, architecture provides power efficiently considering the SoCs performance.

But even if Apple pulls off meaningful improvements in battery conservation in the iPhone 6, the allegedly sleeker profile of the company's next-generation smartphone lineup could put too much limitation on battery sizes for the company to become a trendsetter in mobile phone battery life.

Consumers care about battery life
Several recent surveys suggest battery life will be an important factor in purchasing decisions for the iPhone 6.

One study by RBC Capital Markets (via MacRumors) found that the main driving factor behind potential sales of the iPhone 6 was battery life, getting 33% of the votes among other features like larger screen size, an improved processor, and a better camera.

A survey by coupon site WalletHero had similar conclusions. Among the 1,500 who were asked the question (which allowed for multiple answers), "What Features/Changes Would Make You Purchase the New iPhone?" battery life was the most popular response, with 97% of respondents saying it would be a feature that would help convince them to by the phone.

Apple's biggest competitor, Samsung, knows how important battery life is to consumers. That's why it recently unveiled a new marketing campaign aimed at the iPhone's relatively worse battery life than its Samsung Galaxy S5.

Will Apple be able to deliver on this important feature with the iPhone 6? A sleeker design that allegedly limits battery power will require Apple to make significant progress in battery conservation in order to impress consumers.