The difference between 10000 vs 20000 mAh is simple: a 20000 mAh power bank stores about twice the energy, so it gives roughly twice the phone charges, but it is also about twice as heavy and takes twice as long to refill. A 10000 mAh pack suits daily carry; 20000 mAh suits outages, travel and two phones.
How many phone charges each gives
No power bank delivers its full rating. Energy is lost converting the battery’s voltage to USB and as heat, so expect about 60–70% of the label to reach your phone. If the numbers on the label confuse you, start with what mAh actually means.
| 10000 mAh | 20000 mAh | |
|---|---|---|
| Usable for your phone | about 6,000–7,000 mAh | about 12,000–14,000 mAh |
| Charges of a 5,000 mAh phone | about 1.2–1.4 | about 2.4–2.8 |
| Charges of a 3,500 mAh phone | about 2 | about 4 |
| Typical weight | about 180–250 g | about 350–450 g |
| Refill time (18–20 W input) | about 3–4 hours | about 6–8 hours |
The same logic answers smaller comparisons such as 5000 vs 6000 mAh phones: 20% more capacity means about 20% longer screen time, not a different class of phone.
How many hours does it last?
“10000 mAh means how many hours” depends on what you plug in, not the power bank alone. Rough guides:
- Phone in normal use: a 10000 mAh pack adds roughly one extra day; 20000 mAh adds about two.
- Wi-Fi router during a KPLC blackout: most home routers draw around 6–12 W and need a USB-to-12 V boost cable (check the voltage on your router’s adapter). Expect roughly 3–4 hours from 10000 mAh and 6–8 hours from 20000 mAh.
- Phone plus router together: split the hours accordingly.
Size, weight and charging time
Weight is the real trade-off. A 10000 mAh pack fits a pocket; a 20000 mAh pack is closer to a small brick and lives in a bag. Faster input (USB-C Power Delivery, 20 W or more) cuts refill time noticeably, which matters when power comes back for only a few hours.
Both sizes are allowed in hand luggage on flights because they sit well under the usual 100 Wh limit; see power banks on planes for the rules.
Which suits power cuts, travel or daily carry
- Daily carry, matatu commutes, one phone: 10000 mAh.
- Frequent outages, keeping a router alive, upcountry trips: 20000 mAh.
- Two phones or a phone and tablet: 20000 mAh.
- Charging a laptop: neither size by default; you need a pack with high-wattage USB-C output.
To size one exactly for your phone, use the formula in what mAh power bank do I need.
Quick answers
A 20000 mAh power bank holds about twice the energy, so it gives about twice the charges, but it weighs roughly twice as much and takes about twice as long to recharge.
It depends on the device. It adds about a day of normal phone use, or roughly 3–4 hours to a typical Wi-Fi router through a 12 V boost cable.
At around 350–450 g it is too heavy for most pockets but fine in a bag. If you mainly need it at home during outages, the weight does not matter.
