How to Choose a Power Bank in 2025: Capacity, Output & Real-World Testing

TL;DR

Wh matters more than mAh; expect 60-70% usable capacity after conversion losses

Match output wattage to devices: 22.5-30W for phones, 65W+ for laptops

Stay under 100Wh (≈26,800mAh) to keep power banks flight-legal

Buy reputable brands and check safety certifications

Quick jumps: Capacity math | Output power | Common mistakes | Bottom line

Why Power Bank Specs Are Confusing

You've seen the marketing: "30,000mAh SUPER POWER!" But that same power bank only charges your phone 4 times. What gives?

The power bank industry uses specifications that are technically accurate but practically misleading. Understanding the reality helps you make better purchases.

Capacity: mAh vs. Wh (The Real Story)

mAh (milliampere-hours) is how most power banks are marketed. It measures electrical charge—how much "stuff" the battery can store.

Wh (watt-hours) measures actual energy. This is what determines how many times you can charge your phone.

The conversion: Wh = mAh × Voltage ÷ 1000

Here's where it gets tricky: power bank cells store energy at 3.7V, but they output at 5V (or higher for fast charging). Energy is lost in the voltage conversion.

Practical Example

A 10,000mAh power bank at 3.7V contains 37Wh of energy. But when outputting at 5V, you only get about 30-32Wh due to conversion losses. Additional losses occur in the cable and your phone's charging circuitry.

Net result: A 10,000mAh power bank delivers roughly 6,000-7,000mAh to your phone. Marketing shows theoretical capacity; reality delivers 60-70% of that.

Flight Restrictions: Why 26,800mAh Is the Magic Number

Airlines (following FAA/TSA guidelines) limit lithium batteries to 100Wh for carry-on luggage. Here's the math:

100Wh ÷ 3.7V × 1000 = 27,027mAh

That's why you see so many power banks rated at exactly 26,800mAh—it's the maximum capacity allowed on flights with comfortable safety margin.

Power banks over 100Wh require airline approval and are limited to two per person. Power banks over 160Wh are completely prohibited on passenger aircraft.

Practical advice: If you fly regularly, stay at or below 26,800mAh to avoid any hassles with security or gate agents.

Output Power: Why Wattage Matters More Than Capacity

A high-capacity power bank with low output is frustratingly slow. Output wattage determines charging speed:

Phone Charging Speeds

5W (USB-A standard): 3+ hours for full charge

18W (QC 3.0 / PD): ~1.5 hours for full charge

27W+ (fast charging): Under 1 hour for most phones

65W+ (ultra-fast): 30-40 minutes for compatible phones

Laptop Charging Realities

20W output: Can maintain laptop charge while sleeping

45W output: Slow charging while light use (web browsing, documents)

65W output: Reasonable charging during medium use

100-200W output: Full-speed charging for most laptops (new high-power options in 2026)

Critical point: Your power bank's capacity drains faster at higher output. A 20,000mAh bank outputting 65W might only provide 2 hours of laptop extension. That's still valuable, but set realistic expectations.

Input Power: Don't Overlook This

How fast can you recharge your power bank? Input wattage matters, especially for larger capacities.

15W input: Fine for 5,000-10,000mAh banks (2-4 hours recharge)

30W input: Good for 10,000-20,000mAh banks (2-3 hours recharge)

65W+ input: Necessary for 20,000mAh+ banks if you don't want overnight recharging

140W+ input: New in 2025, allows rapid recharging of large capacity banks

Look for pass-through charging: Some power banks can charge devices while being recharged themselves. This lets you plug the power bank into a wall charger, then plug your phone into the power bank—maximizing one outlet.

Form Factor Considerations

Power banks come in several physical designs, each with trade-offs:

Slim Stick Style

Fits in pocket alongside phone

Usually 5,000-10,000mAh

Limited output power (typically 10-30W)

Best for: Daily carry, emergency backup

Brick Style

Higher capacity (10,000-27,000mAh)

Multiple ports, higher output

Too large for pockets

Best for: Bag storage, travel, laptop charging

Multi-Device/Station Style

30,000mAh+ (may not be flight-legal)

Multiple high-power outputs

Often includes AC outlet

Best for: Camping, group charging, extended off-grid use

MagSafe/Magnetic Style (Popular in 2025)

Attaches directly to compatible phones

Usually 5,000-10,000mAh

Wireless + wired charging options

Best for: iPhone and compatible Android users

Real-World Testing vs. Specifications

When evaluating power banks, be skeptical of maximum specifications. Here's what to look for:

Signs of a Quality Power Bank

Consistent output under load: Some cheap banks drop from 18W to 5W when battery is half-drained

Accurate capacity claims: Premium brands (Anker, UGREEN, Belkin) typically deliver 70-75% usable capacity; cheap brands might only deliver 50-60%

Temperature management: Quality banks stay cool under sustained output; cheap ones get hot

Safety certifications: Look for UL, CE, or FCC marks

Red Flags

Implausibly cheap pricing: A legitimate 20,000mAh 65W power bank costs $40-70. If you find one for $15, the capacity is probably fake.

No brand name: Completely unbranded power banks often use recycled cells with degraded capacity

"Solar charging" as primary feature: Solar panels on power banks are usually 1-2W—enough to maybe add 1% charge per hour in direct sunlight. They're marketing gimmicks, not practical charging solutions.

My Power Bank Recommendations for 2026

Everyday Carry (EDC)

Need: Small, pocketable, emergency backup

Recommendation: Anker Nano Power Bank 5,000mAh with 22.5W output

Expected performance: One full phone charge, pocket-friendly size

Budget: $20-30

Travel & Commuting

Need: Multiple phone charges, bag storage

Recommendation: Anker PowerCore 10,000mAh with 30W output

Expected performance: 2-3 full phone charges, reasonable size

Budget: $30-45

Laptop Power Extension

Need: Extra hours of laptop use, high output

Recommendation: Anker Prime 20,000mAh with 65W output or UGREEN Nexode 20,000mAh

Expected performance: 2-3 hours additional laptop use, 4+ phone charges

Budget: $50-80

Maximum Portable Power

Need: Long flights, camping, group charging

Recommendation: Anker Prime 26,800mAh with 200W output

Expected performance: Full laptop charge + multiple phone charges, ultra-fast charging

Budget: $100-150

Common Power Bank Mistakes

Mistake #1: Buying based on mAh alone

A cheap 20,000mAh bank might deliver less actual energy than a quality 10,000mAh bank.

Mistake #2: Ignoring output power

If you have a fast-charging phone but a 10W-output power bank, you're wasting your phone's capabilities.

Mistake #3: Leaving power bank fully drained

Lithium batteries degrade faster when stored at very low charge. Keep your power bank at 30-80% when not in use for long periods.

Mistake #4: Expecting laptop-like charging speeds

Physics limits how fast power banks can discharge safely. Even a 200W power bank doesn't charge as fast as a wall charger in practice.

The Bottom Line

For most people, a 10,000mAh power bank with 22.5-30W output offers the best balance of capacity, speed, and portability. It'll fully charge your phone twice, fits easily in any bag, and costs under $45 from reputable brands.

If you regularly use a laptop away from outlets, invest in a 20,000mAh 65W unit. Yes, it costs more and weighs more—but having 2-3 extra hours of productivity is worth the trade-off.

For maximum power, the new 200W output power banks from Anker Prime series are game-changers for laptop users who need serious portable charging capability.

Skip the gimmicks (solar panels, built-in cables, wireless charging on budget models). Focus on capacity, output power, and build quality from known brands. Your future self—stuck at 5% battery during an important moment—will thank you.

Data Sources: Airline lithium battery guidelines (FAA/TSA), manufacturer specifications, and aggregated user reviews. Last verified: 2026-01-08.