How to Compare Power Banks | Beyond the mAh Number

Compare power banks by watt-hours, output wattage, and recharge speed, not just milliamp-hours, to find one that truly fits your devices and travels well.

Most power bank listings shout milliamp-hours, but that number tells a partial story. Comparing power banks on the mAh figure alone is a trap: a 10,000 mAh pack from one brand can technically hold different energy than another with the same label. The measure that matters is watt-hours — true energy capacity. Whether you’re charging a phone on a commute or a laptop on a flight, three numbers decide the right pick: Wh for capacity, output wattage for what it can charge, and input wattage for how fast it refills.

Why Watt-Hours Beat Milliamp-Hours

Watt-hours communicate actual energy, so they translate directly into real-world use. The rough conversion is Wh = (mAh × voltage) / 1000. For common sizes, that works out to:

• 10,000 mAh (≈37 Wh): One to two phone charges; pocket-friendly.
• 20,000 mAh (≈74 Wh): Several phone charges or one laptop top-up; bag-sized.
• 24,000 mAh (≈86.4 Wh): Heavy-duty multi-device charging; still under the 100 Wh air-travel line.

Capacity also sets your travel rules. The TSA requires power banks to go in carry-on bags, and current airline guidance allows packs under 100 Wh without special approval. Units between 100 and 160 Wh usually need airline approval, so a larger pack can be a boarding headache.

Output and Input: Charging Speed Is a Two-Way Street

Output wattage tells you what the bank can actually power. Phones typically charge fine at 20W or more, while laptops need 60–100W USB-C Power Delivery (PD). Buying a high-capacity pack with a weak output means a laptop that won’t charge or a phone that trickles.

Input wattage governs how fast the bank itself refills. Look for 20W+ USB-C PD input, or a giant pack becomes a multi-hour charging project. A quick check before buying: match the cable’s wattage rating to both bank and device, and for 100W-and-up units, the cable should carry an e-marker chip to handle the power safely.

The Safety and Port Checklist

Protection features separate a sound buy from a risk. Current safety guidance from the Australian and UK authorities converges: buy from reputable sellers and confirm over-voltage, over-temperature, and short-circuit protection.

Port mix is the last practical filter. Confirm your device’s port type — USB-C is the norm — and count what you’ll charge at once. A 20,000 mAh unit with two ports serves phone-plus-earbuds; an 86.4 Wh unit with multiple high-wattage ports serves a whole travel kit. If you’re ready to buy, our roundup of top-rated 45W power bank picks covers models that balance laptop charging with portability.

Common Comparison Mistakes Worth Skipping

Most bad purchases trace to four recurring errors. Comparing mAh alone ignores true energy; buying a huge pack without checking the 100 Wh travel line invites airline friction; pairing a high-output bank with an under-specified cable strangles the charge; a weak wall charger turns a fast-refill bank into a slow one. The fix is simple: verify Wh, output, input, and cable spec before checkout, and you’ll buy a bank that works now and survives your next flight.