Does leaving a phone charger plugged in cost anything at all?
A modern phone charger left plugged in with nothing attached draws at most 0.1 watts by law, which is 0.876 kilowatt hours over a full year and 22.9p at the Ofgem cap rate of 26.11p per kWh. An older charger measured at 0.26 watts costs 59.5p a year, so even a houseful of them is under three pounds.
The number, and where it comes from
This question has a legal answer rather than an estimated one, which makes it unusually easy to settle.
Ecodesign rules for external power supplies, retained in UK law as Regulation 2019/1782, state that an alternating to direct current adapter rated at 49 watts or less must not draw more than 0.10 watts with nothing connected. Every phone charger in your house falls under that limit, including the Apple 20 watt USB-C adapter that ships with most iPhones. Manufacturers design to the rule with a little room to spare, so the real figure is usually lower.
Older chargers predate the rule. Measurements by Berkeley Lab put the average no load draw of the previous generation at 0.26 watts, and independent bench tests of a drawer full of assorted chargers found a spread of 0.1 to 0.5 watts. A charger sold in 2002 might have drawn 3 watts, which is where this whole worry started.
Work it out for your own phone charger left plugged in
Type in the wattage from the plate on the back, then your own unit rate. The numbers update as you type.
What that costs over a year
| Charger | No load draw | Per day | Per month | Per year |
|---|---|---|---|---|
| Modern charger at the legal limit | 0.10 W | 0.06p | 1.9p | 22.9p |
| Typical older charger | 0.26 W | 0.16p | 5.0p | 59.5p |
| Worst case in bench testing | 0.50 W | 0.31p | 9.5p | £1.14 |
| Ten modern chargers in one house | 1.00 W | 0.63p | 19.1p | £2.29 |
| A charger from 2002 | 3.00 W | 1.9p | 57.2p | £6.86 |
Only the bottom row ever justified the habit of unplugging, and those chargers went out of production two decades ago.
| Appliance | Typical draw | Usage we assume | Per hour (UK) | Per usage (UK) | Per month (UK) | Per hour (US) |
|---|---|---|---|---|---|---|
| Phone charger left plugged in | 0.1 W | per 24 hours plugged in with no phone attached | 0.00p | 0.06p | 1.9p | 0.00 cents |
Rates: Ofgem cap 1 July to 30 September 2026 at 26.11p per kWh (source), EIA residential average June 2026 at 18.34 cents per kWh (source). Checked 2026-09-22.
The sum, for anyone who wants to check
Take the watts, divide by a thousand, multiply by the hours, multiply by your rate.
A charger at 0.1 watts is 0.0001 kilowatts. Multiply by 8,760 hours in a year and you have 0.876 kilowatt hours. Multiply by 26.11p and the answer is 22.9p. Even the pessimistic 0.5 watt case gives 4.38 kilowatt hours and £1.14, which is roughly the price of a single tumble dryer cycle.
Charging the phone itself is the larger figure, though still tiny. A modern phone battery holds somewhere between 15 and 20 watt hours, and conversion losses add roughly a fifth on top, so a full charge from flat costs about half a penny. Daily charging for a year comes to around £1.91.
Where the same worry is worth having
The instinct behind this question is sound. Things left plugged in do cost money, just not this thing. If you want the habit to pay, point it at the appliances that actually draw power while idle.
- A broadband router runs at about 10 watts around the clock, which is 87.6 kilowatt hours and £22.87 a year, a hundred times a charger.
- A television on standby at half a watt costs £1.14 a year, and an older set with an instant on feature can cost several pounds.
- A set top box or games console in rest mode can draw more overnight than the television it is attached to.
- A gaming PC left at the desktop rather than asleep draws around 80 watts and costs about £15 a month, which makes it the largest silent cost in any home that has one.
- An electric shower, a tumble dryer and a kettle cost more in a week than every charger in the house costs in a decade.
Why you cannot measure this at home
Anybody who tries to check these figures with a plug in energy monitor gets the same result, which is zero. That is not proof the charger draws nothing, it is the meter telling you the truth about itself. Most consumer energy monitors have a starting threshold somewhere between half a watt and three watts, so a 0.1 watt load sits below the point where the meter registers anything at all.
Laboratories measure no load power with equipment that averages current over long periods under controlled voltage, which is how Berkeley Lab arrived at the 0.26 watt figure and how manufacturers certify compliance with the 0.10 watt limit. If you want a home approximation, plug six chargers into one extension lead and read the monitor, then divide, and accept that you are still measuring the extension lead as much as the chargers.
The useful takeaway is that an appliance your meter cannot see is an appliance your bill cannot feel. Anything worth chasing shows up on a cheap monitor within a second of plugging it in.
What it costs in the United States
At the EIA residential average of 18.34 cents per kilowatt hour, a charger at the 0.1 watt limit costs 16 cents a year. Even in California, where residential electricity runs close to 35 cents, the figure is 30 cents. Ten chargers in a Californian home, left plugged in permanently for twelve months, cost $3.04.
American chargers sold since 2016 meet Department of Energy Level VI efficiency rules, which set similar no load limits to the European ones, so the same conclusion holds on both sides of the Atlantic.
The honest verdict
Leaving a phone charger plugged in costs about as much per year as one slice of bread. The advice to unplug them survives because it sounds thrifty and because it was genuinely true in 2002, not because the arithmetic still supports it.
The one reason to unplug that does still stand is safety with cheap unbranded adapters, which have been the subject of repeated fire service warnings. Buy a charger with a recognised brand on it and leave it where it is, then go and put the gaming PC to sleep, because that is where the £15 a month is hiding.
Common questions
How much electricity does a phone charger use when not charging?
Almost none. Ecodesign rules that apply in the UK and the EU cap no load consumption at 0.10 watts for any adapter rated 49 watts or less, which covers every phone charger sold. That is 0.0024 kilowatt hours a day, or six hundredths of a penny.
How much electricity does a phone charger use per month?
At the legal limit of 0.1 watts, a charger left plugged in all month uses 0.073 kilowatt hours and costs 1.9p. An older charger drawing 0.26 watts costs 5p a month. Ten of them scattered around the house come to 19p a month at worst.
Does a phone charger use a lot of electricity while it is actually charging?
A full charge of a modern phone takes roughly 0.02 kilowatt hours once conversion losses are counted, which is about half a penny. Charging every day for a year costs around £1.91, so the charging itself costs more than eight years of leaving the charger plugged in.
Is it worth unplugging phone chargers to save money?
Not on the electricity, no. The saving is under 25p a year per charger, which is less than the value of the time spent doing it. There is a mild safety argument for unplugging cheap unbranded chargers, and that one is worth taking seriously, but it is a fire question rather than a bill question.