Power Bank Buying Guide 2026: Capacity, Wattage, and Airline Rules Explained

The Capacity Deception: mAh vs Wh

Power banks are marketed in mAh (milliamp hours).

This unit is only meaningful at a specific voltage, and power banks output at multiple voltages (5V, 9V, 12V, 15V, 20V depending on device negotiation).

The correct unit for comparing power bank capacity is Wh (watt hours).

Every power bank that ships for sale in the EU must display Wh.

In the US, many manufacturers display only mAh.

Matching Wattage to Your Device

For smartphone charging only (27W max for most modern phones): Any 18W+ USB-C PD power bank is adequate The bank's capacity (mAh/Wh) determines how many charges you get Output wattage above 30W is not useful for phone-only use For iPad Pro charging (45W max):

Fast Charging Standards: What They Mean

Multiple fast charging standards exist and they are not all compatible: USB Power Delivery (USB-PD): the universal standard.

Works with all USB-C devices that support fast charging (iPhones, iPads, MacBooks, most modern Android phones, Windows laptops).

All power banks in this guide support USB-PD.

Qualcomm Quick Charge: proprietary standard for Qualcomm Snapdragon-based Android phones.

Many power banks support QC 3.0 or QC 4.0.

The Airline 100Wh Limit: Exact Rules

US DOT (Department of Transportation) lithium battery regulations, which apply to commercial flights: Under 100Wh: allowed in carry-on without airline approval 100-160Wh: allowed in carry-on with airline approval (contact carrier before travel) Over 160Wh: generally prohibited on commercial flights The 100Wh threshold: approximately 27,000mAh at 3.7V.

Passthrough Charging: When It Matters

Passthrough allows a power bank to charge from the wall while simultaneously outputting to a device.

One outlet, two devices (charge power bank and phone simultaneously from one adapter) Power bank runs low during a meeting, charge it and keep it connected to your laptop Passthrough efficiency varies: some banks throttle output significantly when charging themselves.

The Anker 737 maintains good output wattage during pass-through.

Check reviews for watt-meter measurements if this feature is important.

Number of Ports and Simultaneous Charging

For single-device charging: one port is sufficient.

For travel with multiple devices: two USB-C ports allows simultaneous laptop + phone charging.

Important: total output wattage is typically shared across ports.

A 140W power bank with two USB-C ports may deliver 100W + 30W simultaneously, not 140W + 140W.

Check the spec sheet for simultaneous multi-port wattage.

Recharge Time for the Power Bank Itself

Often overlooked: how long does it take to recharge the power bank?

10W input on 20,000mAh bank: 12-14 hours (overnight minimum) 65W input (Anker 737): 2.5 hours For daily commuters who recharge overnight: input wattage is irrelevant.

For travelers who might need to recharge mid-trip: look for 45W+ input.

Size and Weight for Daily Carry

Three size categories for everyday use: Pocket power banks (under 200g, under 10,000mAh): fits in jeans or jacket pocket.

Does not charge laptops effectively.

Good for: day trips without a bag.

Bag power banks (200-500g, 10,000-20,000mAh): fits in any laptop bag or backpack.

Charges phones 3-5 times, most laptops once at 65-100W output.