A useful power bank comparison starts with rated Wh, measured USB output Wh, device-compatible charging profiles, port sharing, recharge input, size, weight and safety documentation. Do not compare products by mAh or peak wattage alone, and do not call one model the longest-lasting without the same load and test method.
Convert mAh to Wh Before Comparing Capacity
mAh is incomplete without the battery’s nominal voltage. Use Wh = mAh × V ÷ 1,000 to compare stored energy. Then keep rated cell Wh separate from measured USB output Wh. Conversion losses, the selected output voltage, cable resistance, temperature and device charging losses all affect the energy that reaches a phone or laptop.
The mAh-to-Wh calculator provides the unit conversion. A product comparison should record the exact nominal voltage shown on each label rather than assuming every pack uses the same value.
Match Output Profiles to the Devices
Record each fixed USB Power Delivery PDO, PPS range and per-port maximum. A high total wattage does not prove laptop compatibility, and it does not mean every port supplies that power simultaneously. Compare one-port and multi-port allocations, then check the input profile used to recharge the bank.
| Metric | Comparable record | Avoid |
|---|---|---|
| Capacity | Rated Wh and measured output Wh | mAh alone |
| Charging | Exact PDO/PPS profiles | “Fast charging” without profiles |
| Multiple devices | Allocation for each port combination | Total wattage assigned to every port |
| Portability | Maximum dimensions and complete-unit weight | “Compact” without measurements |
| Runtime/cycles | Same load, cutoff, environment and sample method | Unattributed category averages |
Use One Method for Every Candidate
| Field | Model A | Model B |
|---|---|---|
| Rated Wh / measured USB Wh | Record | Record |
| USB-C input and output profiles | Record | Record |
| C1 + C2 allocation | Record | Record |
| Recharge time and test adapter | Record | Record |
| Weight and maximum dimensions | Record | Record |
| Peak temperature at stated load/ambient | Record | Record |
| Label and exact safety records | Record | Record |
Keep model identity, sample count, equipment and test date with the scorecard. A vendor specification can populate a declared field, but only a comparable measurement should be labelled as a test result.
Choose the Smallest Product That Completes the Task
- Daily phone use: prioritize weight, pocket fit and the phone’s fast-charge profile.
- Phone plus tablet: verify simultaneous allocation and enough stored Wh.
- Laptop: confirm the required voltage profile and sustained output.
- Travel: check printed Wh and airline rules before packing.
- Wireless model: compare alignment, wireless output and the remaining energy for wired ports.
For phone-specific choices, continue with the power banks for phones guide. This page owns the comparison method, not a changing “best model” ranking.