Charging cost comes down to a simple formula: energy used (in kWh) × your electricity rate (in $/kWh). A full charge for a tablet uses roughly 0.03 kWh of energy under typical conditions.
| Electricity Rate | Cost per Full Charge |
|---|---|
| $0.12/kWh (low) | $0.004 |
| $0.16/kWh (US average) | $0.005 |
| $0.25/kWh (high) | $0.007 |
| $0.35/kWh (peak/premium) | $0.01 |
Charger efficiency losses (typically 10-20%) mean the wall draws slightly more than the device actually stores — the table above already reflects realistic wall-side consumption, not just battery capacity.
Why it matters
Even at premium electricity rates, charging a tablet costs a small fraction of equivalent gasoline or replacement-battery costs — the practical impact on a monthly bill is usually minor unless charging very large packs (like EVs) frequently.