How Much Does It Cost to Charge a USB Phone Power Bank in the UK? (2026 Guide)
Charging a typical 10,000mAh USB phone power bank costs approximately 1.2p in the UK. A 20,000mAh model costs around 2.4p. Both estimates use the October–December 2026 average capped electricity rate of 26.32p/kWh, assuming 80% charging efficiency.
Power bank charging costs at a glance
Approximate cost to recharge from empty using the average standard-variable electricity unit rate for households paying by Direct Debit in England, Scotland and Wales.
| Power bank capacity | Stored energy (3.7V) | Cost per full charge |
|---|---|---|
| 5,000mAh | 18.5Wh | 0.6p |
| 10,000mAh | 37Wh | 1.2p |
| 20,000mAh | 74Wh | 2.4p |
| 26,800mAh | 99.2Wh | 3.3p |
Assumptions: 3.7V nominal battery voltage, 80% efficiency from the wall socket into the power bank, and 26.32p/kWh. Estimates exclude the daily standing charge. Your tariff, product specifications and losses will change the result.
Power bank charging-cost calculator
Enter the power bank capacity and the electricity unit rate from your bill, then click Calculate cost to update the green result.
Estimated wall electricity: 46.3Wh
At one full recharge per week: 63.3p per year (52 charges).
This tool calculates electricity used to refill the power bank, not the extra losses when the power bank subsequently charges a phone. It is an estimate, not a measurement from a smart plug.
How we calculated the 1.2p figure
A power bank rated at 10,000mAh does not contain 10kWh of electricity. First convert its capacity to amp-hours (Ah), then multiply by the internal battery’s nominal voltage to find watt-hours (Wh).
10Ah × 3.7V = 37Wh stored in the cells
37Wh ÷ 0.80 estimated charging efficiency = 46.25Wh from the socket
46.25Wh ÷ 1,000 = 0.04625kWh
0.04625kWh × 26.32p/kWh = 1.2173p ≈ 1.2p
We use watt-hours because mAh by itself does not account for battery voltage. Some power banks use different nominal voltages or report a separate Wh rating, which should take priority when available.
Common questions about charging costs
Does a 20W or 45W USB-C charger cost more?
Not necessarily much more for the same refill. Higher wattage can shorten charging time, but the total energy used depends mainly on the energy being replaced and real efficiency.
What if I have a cheaper overnight tariff?
Enter your off-peak unit rate in the calculator. Charging at a lower price per kWh reduces the electricity cost; the power bank’s capacity stays the same.
Why might my actual cost differ?
Power banks may start partly charged; cell voltage, charger efficiency, standby use and battery condition vary. The calculator assumes a complete recharge from empty.
Does this include charging my phone afterwards?
No. Energy is also lost when electricity travels from the power bank into the phone. These figures only estimate the mains electricity needed to refill the power bank itself.
Which power banks are popular on Amazon UK?
We capture dated Amazon UK bestseller snapshots and record changes in our Top 5. You can compare the current ranked products and see their historical positions — without confusing bestseller popularity with independent hands-on testing.
See the Amazon UK Top 5 Power Banks →Sources and assumptions
UK electricity price: Ofgem — electricity price cap unit rates and standing charges. National average of 26.32p/kWh for standard-variable single-rate electricity paid by Direct Debit, 1 October to 31 December 2026. This is a Great Britain average, not a universal UK tariff; Northern Ireland has different arrangements.
mAh and watt-hours: TP-Link — Understanding the capacity and efficiency of a power bank. The 3.7V cell value is a typical illustrative assumption. We independently calculate the costs; 80% mains-to-battery efficiency is our stated estimate, not a measured figure or manufacturer guarantee.
Editorial note: First published 12 October 2026. We intend to check the displayed rate when Ofgem changes its quarterly cap. If the quoted period has ended, use the calculator with your current tariff instead. Our power bank bestseller charts contain dated snapshots, not continuous sales tracking.