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01Phone charging cost calculator
Default rate is $0.17 per kWh. Your bill lists your actual rate, sometimes split into supply and delivery charges; add them together.
Charging a phone costs about a third of a cent each time, so even a heavy user who charges twice a day spends only a few dollars a year. The calculator shows your exact figure once you put in your own rate.
The reason is simple: phone batteries are tiny. A 4,500 mAh battery holds around 17 watt-hours. A kettle uses that much energy in well under a minute.
02How the math works
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Turn mAh into watt-hours
Multiply the battery's mAh by its voltage (about 3.85 V for modern phones) and divide by 1,000. 4,500 mAh × 3.85 ÷ 1,000 ≈ 17.3 Wh.
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Add the losses
Chargers and the phone's own circuitry waste some energy as heat. Divide by 0.8 to cover it: 17.3 ÷ 0.8 ≈ 21.7 Wh from the wall.
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Convert to kilowatt-hours
Divide by 1,000. That's about 0.022 kWh per full charge.
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Multiply by your rate
At $0.17 per kWh, 0.022 × 0.17 ≈ $0.0037. Call it a third of a cent.
Yearly cost ≈ mAh × 3.85 ÷ 1,000,000 ÷ 0.8 × charges per day × 365 × $/kWh4,500 mAh, once a day, $0.17/kWh ≈ 7.9 kWh ≈ $1.35 a year.
Want to understand the units behind that formula? Watts, volts and amps and mAh vs Wh explain them without the physics lecture.
03Your phone vs the rest of the house
Same $0.17 rate, worked out from typical power draws. Your appliances will differ, but the scale won't.
| Device and use | Energy per year | Cost per year |
|---|---|---|
| Phone, one full charge a day | About 8 kWh | About $1.35 |
| Phone, two charges a day | About 16 kWh | About $2.70 |
| 10W LED bulb, 5 hours a day | About 18 kWh | About $3.10 |
| 45W laptop charger, 4 hours a day | About 66 kWh | About $11 |
| 100W TV, 4 hours a day | About 146 kWh | About $25 |
Charging a phone every day for a year costs less than leaving one LED bulb on in the evenings. If you're trimming your power bill, look at heating, cooling and old appliances first.
04Wireless, overnight and idle chargers
- Wireless charging wastes more energy than a cable, especially if the phone sits off-center or the case is thick. Expect a noticeably higher bill line, still well under a few dollars a year for one phone.
- Overnight charging doesn't keep pulling full power. Once the battery is full the phone draws only a trickle, so a night on the charger costs about the same as an hour.
- A charger with nothing plugged in draws a tiny amount. Modern USB-C bricks typically idle at a fraction of a watt, which works out to pennies a year.
- Power banks add another round of losses. Charging the bank, then the phone from the bank, can cost close to double per charge. Still fractions of a cent.
Electricity in some states costs twice the national average or more. Plug your own rate into the calculator. Even at double, one phone stays under about $3 a year.
05Where your charging money really goes
Electricity is the cheapest part of charging. The charger and cable cost far more, so the money-saving move is buying ones that last. A fraying cable or a cheap brick that dies in six months costs more than ten years of electricity.
Spend once on a USB-C PD charger from a seller that lists clear specs, and a braided cable that survives being yanked out of the wall. Avoid no-name chargers with no safety markings; our guide to spotting a fake charger shows what to check.
A fast USB-C charger, a braided cable and a magnetic pad for the nightstand.
Questions people ask
How much does it cost to charge a phone for a year?
About $1 to $2 for one full charge a day at typical US electricity prices. A 4,500 mAh phone charged daily at $0.17 per kWh uses roughly 8 kWh, or about $1.35 a year.
Does leaving a charger plugged in waste electricity?
A little. Modern USB-C chargers draw a fraction of a watt with nothing attached, which adds up to pennies a year. Unplug it if it's old, warm to the touch or buzzing.
Is wireless charging more expensive than wired?
Slightly. Wireless loses more energy as heat, so it takes more from the wall for the same charge. For one phone, the extra is usually well under a dollar a year.
Does fast charging use more electricity?
Not meaningfully. Fast charging delivers the same energy in less time. Efficiency differences between a good 20W and a good 45W charger are small enough to ignore on your bill.
How many kWh does it take to charge a phone?
About 0.015 to 0.03 kWh per full charge, depending on battery size and losses. A 5,000 mAh battery at 3.85 V holds about 19 Wh, so roughly 0.024 kWh from the wall.