Power Banks Ranked: The Ones That Actually Deliver Claimed Capacity

Buy a 20,000 mAh power bank. Charge your phone from 0 to 100%. Do the math: a modern iPhone has roughly a 3,500 mAh internal battery. So you should be able to charge it almost six times. In reality, you get three and a half, maybe four charges. Where did the other capacity go?

Power bank marketing is a semi-fictional genre. The number on the box refers to the internal cells' raw capacity at 3.7V, before any conversion losses. The number on the spec sheet doesn't account for efficiency losses, voltage conversion overhead, and the fact that cold temperatures reduce effective capacity. A "20,000 mAh" power bank typically delivers 12,000 to 14,000 mAh of actual usable energy to your devices.

The result is a category where the spec sheet is a partial lie. Some brands are worse offenders than others. Here are the power banks that actually deliver what they claim, within the honest margins of physics.

The tested category leaders

Anker 737 Power Bank (PowerCore 24K) — $149

The flagship travel power bank. 24,000 mAh rated capacity, 140W PD output. In lab testing, the 737 delivers about 18,000 mAh of actual charge at 5V — that's 75% efficiency, which is at the top of the industry.

The 140W output is genuinely useful. It charges a MacBook Pro at full speed. Total throughput to a laptop, phone, and earbuds simultaneously works well. The built-in display shows remaining capacity and charge rate, which matters more than you'd expect.

Size: about the size of a paperback book. Weight: 630 grams. It's not pocketable but fits in any laptop bag or backpack.

This is the power bank I carry on every trip. It has survived three years of checked baggage, being dropped on airport floors, and being charged via questionable airport outlets. Still works perfectly.

Anker 325 (20,000 mAh, 45W) — $69

The everyday-carry power bank. 20,000 mAh rated, delivers around 14,500 mAh actual (73% efficient). 45W PD output handles an iPad Pro or a phone at top speed. Won't charge a full-size laptop.

Weight: 360 grams. Smaller than the 737, still not pocketable but reasonable in a bag.

The 325 is what I'd recommend to most people. Less expensive than the 737, still handles everyday devices at full speed. The only thing you lose is laptop charging capability.

Ugreen Magnetic Power Bank 10,000 mAh — $54

For iPhone users, magnetic power banks are the convenience king. Snap it to the back of the phone and it charges wirelessly while you keep using the phone. The Ugreen is the best-value magnetic power bank currently available.

Capacity: 10,000 mAh rated. Actual delivery via wireless is about 5,500 mAh to the phone (55% efficient, because wireless charging loses significant energy). USB-C direct delivery is about 7,200 mAh (72% efficient).

Use the USB-C direct output when you have a cable. The wireless charging is for convenience only, not efficiency.

Baseus Blade 100W — $89

The slim format alternative to the Anker 737. 20,000 mAh capacity with 100W output. The form factor is a flat wedge rather than a brick, which slides into a laptop sleeve or a tight backpack compartment.

Efficiency is about 70%, so actual delivery is around 14,000 mAh. Less than the 737 in both capacity and peak output, but more ergonomic for some use cases.

The power banks to actively avoid

Avoid any power bank from an unknown brand on Amazon. Generic "50,000 mAh" power banks at $39 are physically impossible — the cell density required for that capacity in a pocket-sized form factor doesn't exist yet. These products are either fake (actual capacity is 5,000-10,000 mAh) or dangerous (using reclaimed cells in ways that risk fires).

Avoid "solar" power banks. The solar panel is a marketing gimmick. Even in full sun, a 5,000 mAh solar panel takes 30+ hours to charge a power bank fully. The panels are low-quality and the power bank itself is usually a generic low-capacity unit with the solar feature as the only real differentiator.

Avoid power banks from phone manufacturers (Samsung, Xiaomi, etc.) unless you specifically need their ecosystem features. These products are usually overpriced for capacity and underperform dedicated power bank makers in raw efficiency.

Avoid ultra-thin credit-card-sized power banks unless you need one specifically for emergency top-ups. The 5,000 mAh "credit card" form factor is a style decision; the actual delivery is often only 3,000 mAh, which isn't enough for anything serious.

How to calculate what you actually need

Figure out the battery capacity of the devices you're trying to charge:

• iPhone 15-17 series: 3,500-4,500 mAh
• Pixel 8-9 series: 4,500-5,000 mAh
• iPad Pro 11-inch: 7,500 mAh
• iPad Pro 13-inch: 10,000 mAh
• MacBook Air 13-inch: 52 Wh (roughly 14,000 mAh at 3.7V)
• MacBook Pro 14-inch: 72 Wh (roughly 19,500 mAh at 3.7V)

Multiply your device's capacity by the number of full charges you want. Then divide by 0.7 to account for power bank efficiency losses. That's the rated capacity you should buy.

For a phone-only user who wants 2-3 full charges, a 10,000 mAh power bank is sufficient.

For a phone + iPad traveler, 20,000 mAh is the sweet spot.

For a phone + iPad + laptop business trip, 24,000 mAh (with 100W+ output) is the minimum viable product.

The charging speed question

Most people focus on capacity and ignore output speed. That's backwards. A 20,000 mAh power bank that outputs 18W charges your phone over an hour. The same capacity with 45W PD output charges in 30 minutes.

Time to full charge matters at airports, in cars, during short breaks. The faster power bank is the more useful power bank even if capacity is the same.

Minimum output specs to care about in 2026:

• For phones only: 20W PD output.
• For phones + tablets: 30W PD output.
• For MacBook Air: 65W PD output.
• For MacBook Pro: 100W PD output.

A power bank with lower output than your device supports will charge slowly even if it has plenty of capacity.

Airline rules in 2026

Most airlines allow power banks up to 100Wh (approximately 27,000 mAh at 3.7V) in carry-on. No airlines allow them in checked baggage — they must be in your carry-on. Some carriers (varies by country) require a declaration for banks over 100Wh up to 160Wh.

The Anker 737 at 85Wh is under every airline's threshold. The 160Wh category is where specialty workstation power banks live — those require airline-specific paperwork.

I've never been stopped carrying a 737 on any airline. But keep the spec sheet screenshotted in case a security agent asks.

The USB-C port question

Any power bank you buy in 2026 should have USB-C PD input and output. Full stop. If it has only USB-A output, it's not fully usable with modern phones and laptops.

Ideally: two USB-C PD ports plus one USB-A. That covers every device scenario plus backward compatibility.

Avoid power banks with only micro-USB input. You'll waste time looking for micro-USB cables that don't exist in your other devices' charging kits.

The cables that come in the box

Every power bank ships with a short USB-C cable. Most of them are mediocre — low-wattage-rated cables that limit the power bank's output. If you have good USB-C cables already, ignore the included one.

For maximum charge speed, pair the power bank with a cable rated for at least the bank's maximum output. A 140W power bank with a 60W cable will only deliver 60W.

Maintenance that extends life

Store a power bank at 40-60% charge if you won't use it for months. Fully charged or fully depleted storage degrades lithium cells faster.

Keep it out of hot cars. The 120-degree interior of a parked car in summer is above the safe operating temperature for most power bank cells, and repeated exposure reduces capacity permanently.

Don't leave a power bank plugged in after it's full. Modern ones have protection circuits, but cell cycling over many months reduces capacity.

Replace when capacity drops noticeably. Most power banks last 300-500 full cycles (around 3-4 years of regular use). When your power bank charges your phone half as many times as it used to, it's time to retire it.

The power bank category is littered with products that oversell and underdeliver. Stick to Anker, Ugreen, Baseus, and a few other reputable brands. Buy once, with appropriate output specs for your devices, and the power bank becomes invisible — it's in your bag, it works when you need it, it doesn't let you down at 37% battery while you're running late. That's the whole job.