Rechargeable batteries cost more up front and less over time — but only if you use them in the right devices. For some things, disposable alkalines are genuinely the better choice.
The cost-per-use maths
A disposable AA costs roughly 40–80 cents each in a multipack and is used once. A good rechargeable AA (NiMH) costs a few dollars but is rated for hundreds of charge cycles. Over its life it works out to a fraction of a cent per use, plus a small amount of electricity.
The break-even point is usually reached within a year for anything you replace batteries in more than a few times a year.
Where rechargeables win
High-drain and frequently-used devices: game controllers, wireless mice and keyboards, camera flashes, kids’ toys, flashlights you actually use. These flatten disposables quickly, so the savings add up fast.
Low-self-discharge NiMH cells (often sold “pre-charged”) hold most of their charge for months on the shelf, which removed the old complaint about rechargeables going flat in a drawer.
Where disposables still make sense
Low-drain, set-and-forget devices: smoke detectors, wall clocks, TV remotes, emergency flashlights. A disposable alkaline can last years in these, and you do not want a smoke detector on a battery that slowly self-discharges.
Anything you need to work reliably after sitting unused — an emergency kit, a rarely-used tool — is better on fresh alkalines with a long printed shelf life.
Reading the shelf-life claim
“10-year shelf life” on alkaline packaging means the unused battery in storage, not the battery in your device. Once it is powering something, runtime depends entirely on the device’s draw.