It is one of the most reassuring sums in the whole house. A phone feels like it is always plugged in, always drinking power, and it is easy to picture it quietly adding pounds to the bill. It does not. A smartphone holds one of the smallest batteries of anything you own, and charging it is about the cheapest thing electricity does. This guide works out exactly what a full charge costs, what a year of daily charging adds up to, whether wireless or fast charging change the answer, and why the old worry about leaving the charger in the wall is not worth a moment's thought.
The short answer. A full phone charge uses only about 10 to 20 watt-hours of electricity, so at the standard rate of about 26p a unit it costs well under a penny, roughly a third to two thirds of a penny each time. Charge once a day for a whole year and you spend somewhere around 1 to 2 pounds. Even a heavy user topping up twice a day is looking at three or four pounds a year. It is one of the genuinely trivial lines on any electricity bill.
Why a phone costs so little to charge
The whole answer comes down to the size of the battery. A typical smartphone battery holds somewhere between 3,000 and 5,000 milliamp-hours at around 3.85 volts, which works out at roughly 11 to 19 watt-hours of stored energy, or about 0.01 to 0.02 of a kilowatt hour. The kilowatt hour is the unit your meter counts and your supplier bills, so a single full charge is only a fiftieth of a unit or so. Compare that with the appliances that actually drive a bill: a kettle uses roughly the energy of a hundred phone charges every time it boils, and an electric shower can get through several hundred phone charges' worth in a single ten-minute wash. Anything that makes heat dwarfs a phone, because charging a small battery moves a tiny amount of energy and makes almost none.
What a charge costs, and what a year costs
The sum is the same one the running cost calculator does for any device: the energy it uses multiplied by your price per unit. Charging is not perfectly efficient, so a little more comes out of the wall than ends up in the battery, maybe 15 or 20 per cent more, lost as gentle warmth in the charger and the phone. The table folds that in and uses the standard price-cap rate of about 26p per kWh, current in mid 2026.
| How you charge | Energy from the wall | Cost per full charge | Year, charging once a day |
|---|---|---|---|
| Smaller phone (~11 Wh) by cable | ~0.013 kWh | ~0.3p | ~£1.20 |
| Larger phone (~19 Wh) by cable | ~0.022 kWh | ~0.6p | ~£2.10 |
| Larger phone on a wireless pad | ~0.032 kWh | ~0.8p | ~£3.00 |
At an example 26.11p per kWh, the Ofgem price cap for July to September 2026. Assumes a full charge from near empty; most days you top up less than that, so real costs are lower.
Those yearly figures assume a full charge every single day, which most people do not manage, since a phone is usually topped up part-way rather than run flat and filled. In practice the real annual cost of keeping a phone charged is closer to a pound than two for most users. It is the kind of number that disappears into the rounding on a bill dominated by heating, hot water and the tumble dryer.
Does fast charging use more electricity?
No, or so little you will never see it. Fast charging delivers the same amount of energy into the same battery; it just pushes it in more quickly, at higher power for a shorter time. A 20-watt fast charge and a 5-watt slow charge both have to put the same 15 or so watt-hours into the cell, so the cost is the same. Fast charging does run the phone and charger a touch warmer, and heat is wasted energy, so a fast charge can use a hair more from the wall, but the difference is a fraction of a penny and not worth thinking about. Charge speed is about convenience and long-term battery health, not the bill.
Is wireless charging more expensive?
Wireless charging genuinely does use more, because passing energy across a gap through two coils is less efficient than a cable, and the difference shows up as warmth in the pad and the back of the phone. A wireless charge typically draws something like half as much again as a cable, sometimes more, which is why it sits higher in the table. In proportion that sounds dramatic, but in money it is the difference between roughly a third of a penny and roughly three quarters of a penny per charge, or a pound or so a year at daily use. If you prefer the convenience of dropping the phone on a pad, the cost is not a reason to stop. It is worth knowing only because the same inefficiency is why wireless charging warms the phone more, which is the thing that actually matters for the battery.
The plugged-in charger: a myth worth retiring
The classic worry is the charger left in the wall with no phone on the end. It does draw a whisker of power, but on a modern charger it is a whisker indeed. A typical USB plug idles at somewhere between a fiftieth and a quarter of a watt, which over a whole year comes to a few pence up to at most a pound, and that is for a charger left in the socket every hour of every day. Unplugging it is harmless and tidy, but presenting it as a saving is the sort of advice that makes people feel virtuous while the real costs sail past unnoticed. The genuinely hungry always-on devices, like a broadband router or an old set-top box, are where standby power is actually worth chasing, as the full story on standby power explains. The phone charger is not one of them, and the wider crop of energy-saving myths is worth a read for the same reason.
How a phone compares with a tablet or laptop
Scaling up puts the phone in perspective. A tablet holds two or three times the battery of a phone, so a full charge costs about a penny and a bit, and a year of daily charging still comes to only a few pounds. A laptop is the big one of the three: its battery is often 50 to 90 watt-hours, four or five times a phone, so a full charge runs to a penny or two and heavy daily use might reach seven to eleven pounds a year, still modest. What all three share is that they are storing energy in a battery, not making heat, which is why even the laptop, the greediest of the pocket devices, costs less over a year than an electric shower does in a fortnight. If you want to see where the real money goes, the guide to what uses the most electricity in your home ranks it, and the surprise is always how far down the list the gadgets sit.
The bottom line
Charging a phone is about as close to free as any regular use of electricity gets: well under a penny a time, a pound or two a year at daily charging, and no meaningful difference from fast charging. Wireless charging costs a little more but still counts in pennies, and the charger left in the wall wastes almost nothing at all. If you are hunting for savings, this is the wrong end of the house to look. Leave the phone habits alone, plug in the energy monitor instead, and point the effort at the heat: the shower, the heating, the hot water and the dryer, where the pounds actually are.
Common questions
How much does it cost to charge a phone?
Well under a penny per full charge. A smartphone battery holds only about 10 to 20 watt-hours, so at the standard 26p per kWh rate a full charge costs roughly a third to two thirds of a penny. Charged once a day for a year, that is about 1 to 2 pounds.
Does leaving my phone charger plugged in waste electricity?
Almost none. A modern USB charger left in the wall with no phone attached draws a tiny fraction of a watt, adding up to a few pence to at most a pound over a whole year. Unplugging it is tidy but saves next to nothing; the real always-on costs are devices like routers and set-top boxes.
Is wireless charging more expensive than a cable?
Slightly. Charging across a gap is less efficient than a cable, so a wireless charge uses roughly half as much again, which is the difference between about a third of a penny and about three quarters of a penny per charge, or a pound or so a year. In money it is trivial; it matters more because it warms the phone.
Does fast charging use more electricity?
No meaningful difference. Fast charging delivers the same energy into the same battery, just more quickly. It runs a little warmer, so it can use a fraction more from the wall, but the cost difference is a fraction of a penny and not worth considering.