What a phone charger actually draws
A charger topping up a phone overnight draws 2 to 5 W. A modern fast charger can hit 20 to 45 W, but only for the first 20 to 30 minutes of a charge — the window when the battery is deeply discharged and will accept power quickly. After that, the phone tapers deliberately to protect the cells, and draw collapses to under a watt long before the battery reads full.
This is why the number printed on the charger tells you so little. A 45 W brick is a delivery ceiling, reached briefly and rarely. The average across a charging session is far closer to the low end of the range, which is why 5 W is used here as the typical figure with about 3 hours a day of effective charging time.
For scale, DTE's appliance chart lists a cell phone charger at 0.004 kWh — the smallest single line item on the entire utility table. Nothing else a household plugs in is measured in thousandths of a kilowatt-hour.
Then there is the draw everybody asks about: the charger sitting in the wall with nothing attached. This dataset carries 0.2 W for that state, which is already tiny. Measurements of current chargers frequently come in lower still. Either way, it is a number so small that most consumer plug-in meters cannot resolve it reliably.
What that costs, worked through
Watts × hours ÷ 1,000 = kWh per day. For a charger: 5 W × 3 hours = 15 watt-hours, or 0.015 kWh a day. Over 30.4 days that is 0.5 kWh a month, and at the US average rate of 18.44 cents per kWh, that is about 8 cents a month. For the year: roughly 5.5 kWh, or about $1.01.
One dollar. That is the total annual cost of charging a phone at average US rates. Even in the most expensive states, where electricity runs two to three times the national average, it does not clear four dollars.
Per charge, the numbers stop being meaningful in dollars. Thirty minutes at a fast charger's full 45 W is 0.0225 kWh, which is about four tenths of one cent. A full overnight cycle on a slow charger is a fraction of a cent more.
The idle draw deserves its own line because of how often it is cited. At the 0.2 W this dataset carries, a charger left plugged in all year uses 1.75 kWh — about 32 cents. Independent measurements of modern chargers commonly land lower, in the range of 10 to 25 cents a year. The two figures disagree, and the disagreement does not matter: whichever you accept, the answer is small change. If you want to sanity-check that against your own rate, the kWh cost calculator will do it in a few seconds.
What makes the number move
There is less variation here than in any other category on this site, but the factors are worth naming because they are the ones people misjudge.
- Battery size. A large phone or a tablet holds more energy and takes more to fill. A tablet can use several times what a phone does — still measured in cents a year.
- How flat you let it get. Charging from 10 percent moves more energy than topping up from 80. This is the only genuine usage variable.
- Fast charging. Changes the shape of the curve, not the total. A fast charger delivers the same energy into the same battery, just sooner and with slightly more heat lost along the way.
- Charger quality. A cheap, poorly regulated adapter wastes more as heat and idles higher than a well-made one. The difference is real and still trivial in money.
- Wireless charging. Noticeably less efficient than a cable, because energy is lost in the coils as heat. It roughly changes cents into slightly more cents.
What does not move it: leaving the phone plugged in after it reads 100 percent, since the phone stops drawing; charging overnight rather than during the day; or which brand of cable you use.
The one genuine oddity is a charger connected to a phone that is being used heavily — navigation, gaming, video — where the device may consume as fast as the charger supplies and never actually taper.
Whether it is worth doing anything about
No. And this is worth saying plainly, because "unplug your chargers" is one of the most repeated pieces of energy advice in circulation and it is essentially worthless.
A modern charger left plugged in with no phone attached draws well under 0.3 W — roughly 10 to 25 cents of electricity a year. If you unplugged every charger in a typical house every day for a year, you would save less than the price of a cup of coffee, and you would spend real attention doing it. Advice that costs more attention than it returns money is bad advice, however often it is repeated.
The reason the myth persists is that it used to be closer to true. Old linear transformer adapters — the heavy black bricks of the 1990s and 2000s — did draw meaningful idle power. Efficiency standards for external power supplies changed that, and the modern switching charger simply does not behave the same way.
Spend the attention on loads that are genuinely large and genuinely always-on instead: cable and DVR boxes, game consoles left in rest mode, and above all a second refrigerator in the garage, which can quietly run 30 to 40 kWh a month on its own — a hundred times the phone charger, every month, forever. That is the swap worth making: same instinct, applied where the number is big enough to notice. The appliance energy cost calculator will rank them for you.
How it compares with everything else you plug in
At 0.5 kWh a month, the phone charger is the smallest thing on this entire site. It uses less than a single LED light bulb at 0.8 kWh a month. It uses about one-twelfth of a WiFi router's 5.8 kWh, one-eighteenth of a laptop's 9.1 kWh, and one-fiftieth of a desktop computer's 27.4 kWh.
Against household heavyweights the ratios stop being intuitive. A refrigerator at 36.5 kWh a month is roughly 73 chargers. An electric dryer at 54.7 kWh is about 110. An electric water heater at 232.6 kWh is over 460. A central air conditioner at 638.4 kWh in cooling season is more than 1,200 phone chargers running simultaneously.
Put another way: a household could charge every phone it owns, every day, for a decade, and still use less electricity than one summer month of air conditioning. The comparison is not close, and it is not meant to be.
The lesson generalises past this appliance. Energy advice tends to fixate on small, visible, frequently-touched devices, because those are the ones we notice. The bill is set by things that heat, cool or move air and water — and by things that never switch off. A charger is neither. If your bill is rising, look at why your electric bill is so high, and leave the chargers where they are.
Frequently asked questions
How many watts does a phone charger use?
About 2 to 5 watts while topping up a battery. A fast charger is rated 20 to 45 watts, but it only delivers that for the first 20 to 30 minutes of a charge, when the battery is deeply discharged; after that the phone tapers deliberately and draw falls below a watt. The rating on the brick is a ceiling, not a typical figure. DTE's utility chart lists a cell phone charger at 0.004 kWh, the smallest line item on the whole table.
How much does it cost to charge a phone?
Roughly $1.01 a year at the US average rate of 18.44 cents per kWh. The arithmetic: 5 watts for about 3 hours a day is 0.015 kWh, which is 0.5 kWh over a 30.4-day month, or about 8 cents. A single charge costs a fraction of a cent — 30 minutes at a fast charger's full 45 watts is 0.0225 kWh, about four tenths of a cent. Even in the most expensive states in the country, a year of phone charging does not reach four dollars.
Does leaving a charger plugged in waste electricity?
Barely. A modern charger with no phone attached draws well under 0.3 watts, which is roughly 10 to 25 cents of electricity a year; the 0.2 watt figure used in this dataset works out to about 32 cents. Either way it is small change. The advice made more sense in the era of heavy linear transformer adapters, which did idle meaningfully; efficiency standards for external power supplies changed that. Spend the effort on DVR boxes, consoles in rest mode, or a second fridge in the garage instead.
Is wireless charging less efficient than a cable?
Yes. Inductive charging loses energy as heat in the transmitting and receiving coils, and alignment matters — a phone sitting slightly off-centre wastes more. In practical terms it turns a charge costing a fraction of a cent into a charge costing a slightly larger fraction of a cent, so the electricity argument against wireless charging is not a serious one. The real costs are slower charging and more heat in the battery, which matters for battery longevity rather than for your bill.