Power bank marketing is designed to confuse. The mAh number on the box is measured at a voltage your devices don't use; the "fast charge" claim may only apply to one port; and the wattage you need to charge a laptop is completely different from what's needed for a phone. Here is the honest 2026 buying guide.
What changed in 2026
- 100W+ USB-C output is now available in sub-500g power banks — GaN (gallium nitride) efficiency unlocked laptop charging in compact form factors.
- USB PD 3.1 (140W) power banks exist but add weight and cost; most users doing laptop charging are well-served by 65–100W.
- Wireless charging integration improved — mid-range units offer Qi2 (15W) on the reverse side, reducing cable dependence significantly.
- Regulations tightened around high-capacity units — 100Wh airline limits are strictly enforced; some airlines require advance approval above 100Wh.
- Portable power stations (200Wh+) diverged from power banks as a distinct category — see Best portable power stations in 2026 for that tier.
Understanding capacity
The mAh number is measured at 3.7V (the cell voltage). Your USB device charges at 5V. The conversion:
Effective capacity = (mAh × 3.7V × ~0.85 efficiency) / 5V
A 20,000mAh bank delivers ~12,500mAh to a 5V device — roughly 2.5–3 full charges of a modern smartphone. Always calculate from effective capacity, not the advertised number.
| Advertised mAh |
Approx. effective at 5V |
Phone charges |
| 5,000 mAh |
~3,100 mAh |
~0.8 charges |
| 10,000 mAh |
~6,300 mAh |
~1.5 charges |
| 20,000 mAh |
~12,500 mAh |
~3 charges |
| 26,800 mAh |
~16,700 mAh |
~4 charges |
Output wattage guide
| Device |
Minimum useful output |
Recommended output |
| Smartphone |
18W |
25–45W |
| Tablet |
18W |
30–45W |
| Small laptop (13") |
45W |
65W |
| 15–16" laptop |
65W |
100W |
| Gaming laptop |
100W |
140W+ |
Critical: If the power bank's output wattage is lower than the laptop's charging requirement, the laptop will still charge — just slowly, or while continuing to drain battery under load.
How to pick
- Identify the wattage your hungriest device needs. This sets your minimum output spec.
- Decide on size vs. capacity. Jacket-pocket: up to ~10,000mAh at 20W. Backpack daily carry: 20,000mAh at 65W+. Travel with laptop: 26,800mAh at 100W.
- Count ports. Charging two devices simultaneously shares output wattage across ports — check the multi-port spec, not just the max output.
- Check airline compliance. 100Wh is the universal carry-on limit. At 3.7V: 100Wh = ~27,000mAh. Over this requires approval or is prohibited.
- Confirm bidirectional charging. Most modern USB-C power banks charge both ways via USB-C; some older models need a dedicated input port.
Common mistakes
Buying by mAh without checking wattage. A 30,000mAh bank at 10W output is worse than a 20,000mAh bank at 65W output for laptop use.
Using a phone charger to recharge the power bank. A 26,800mAh bank takes 12+ hours to recharge from a 5W USB-A port. Use the highest-wattage charging input the bank supports.
Not checking multi-port power sharing. "65W output" may mean 45W on Port 1 and 20W on Port 2 simultaneously, not 65W per port.
Buying above the airline limit for travel use. Some travelers buy 40,000mAh banks not realizing they can't board. Keep travel banks under 100Wh.
Ignoring pass-through charging support. Some banks can charge a device while being charged themselves (pass-through); others can't. Useful for overnight hotel charging with one outlet.
What to skip
- Power banks with only USB-A output in 2026 — USB-C PD is the standard; USB-A tops out at 18–22.5W which is limiting.
- Ultra-cheap no-brand high-capacity units — lithium cell quality varies enormously; fire risk from swollen or substandard cells is real.
- Solar power banks for serious charging — integrated solar panels on portable banks are too small for meaningful generation; useful only for emergency trickle charging.
FAQ
What's the best capacity for everyday carry?
10,000mAh at 45W handles most phone and tablet needs in a slim form. Add to 20,000mAh if you regularly need multiple charges or carry a laptop.
Can a power bank charge a MacBook or Dell XPS?
Yes, if the output wattage is sufficient. A MacBook Pro 14" draws up to 96W; a 65W power bank will charge it slowly under light use. A 100W bank charges it normally when the screen is at moderate brightness.
How do I check if my power bank is airline-compliant?
Find the Wh (watt-hour) rating on the label. Under 100Wh: carry-on allowed. 100–160Wh: may need airline approval. Over 160Wh: generally prohibited on commercial flights.
How long does a power bank last before the cells degrade?
Quality lithium cells maintain ~80% capacity after 500 charge cycles. At one full charge cycle per week, that's ~10 years. Lower quality cells degrade faster and may swell — store in cool, dry conditions.
Where to go next