In a note to investors on Monday, KGI Securities analyst Ming-Chi Kuo said that Apple could bundle a battery typically reserved for a larger iPhone into a smaller handset. Specifically, Kuo, who has been one of the more reliable sources of Apple (AAPL) rumors in the past, said that the next iPhone—believed to be known as the iPhone 8 or iPhone X—could feature a size similar to the iPhone 7, but use the same-sized battery Apple offers in its substantially larger iPhone 7 Plus.

Battery size is a critical component in battery life. While certain hardware and software features can impact it, in general, the bigger the battery, the longer the battery life. Offering a bigger battery in a smaller frame allows Apple to offer more battery life in its handset without sacrificing size—a common tradeoff when companies want to bundle a bigger battery in their devices.

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The iPhone 7 comes with a 4.7-inch screen and is 5.4 inches tall by 2.6 inches wide. The iPhone 7 Plus, which has a 5.5-inch display, stretches to 6.2 inches tall and is 3.1 inches wide. In addition to its bigger screen, the larger case is designed to accommodate a bigger battery. For that reason, the iPhone 7 Plus can last up to 21 hours during continuous talk time, compared to 14 hours for the iPhone 7.

If Kuo is correct, Apple wants to take the battery that delivers so much more talk time in the iPhone 7 Plus and squeeze it inside a device with dimensions similar to, if not exactly the same as, the iPhone 7.

According to Kuo, whose comments were earlier reported on by Apple-tracking site AppleInsider, Apple could achieve that by redesigning how components are laid out inside the device. Apple might also use smaller components, leaving more room for the battery.

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Kuo’s predictions also shed light on what Apple might have planned for its next iPhone’s design. Kuo said the bigger battery will be offered in the iPhone 8, the long-rumored, but so far not confirmed, big iPhone update Apple has planned for this year. He said that the iPhone 8 will actually be smaller than an iPhone 7s Plus Apple also plans to offer this year, and could come with a 5.1- to 5.2-inch display. That display, he said, will be based on organic light-emitting diode (OLED) and not the liquid-crystal display (LCD) technology Apple has used in the past. OLED is generally more energy-efficient than LCD, which could also boost the smartphone’s battery life.

In addition to new screen technology, Apple is also rumored to be planning an all-glass design for the iPhone 8, along with wireless charging support.