Q. Beloved Umbra,

I know it's supposed to be bad to leave your cell phone charger plugged in when it's non charging, but hither's something I notice myself wondering often: Is it as bad to leave information technology plugged in with your phone fastened after it'southward been charged? And what virtually my laptop charger? Does that leak energy? Can't recollect if you've covered this earlier.

T.Thousand.
Oakland, Calif.

A. Dearest T.Grand.,

I take indeed covered some of this earlier, once or twice, but your question is timely: Just last calendar month, your fine state adopted new free energy-efficiency rules for chargers, citing potential residential and commercial savings of $306 million a year. Too, I am all zinged upwardly by your question about leaving chargers attached to gadgets when their job is done — an important, but often disregarded, variable in this multi-pronged energy equation.

Showtime, a refresher on things that plug in, which allows us to bandy about ii fun terms. "Vampires" are appliances that suck free energy even when you think they're close off, like microwaves, DVRs, TVs, and game systems. Anything with a cute piffling light or digital clock on it is drawing power, commonly unnecessarily, and costing y'all money — one gauge from Cornell University suggests these vampires toll an average household $200 per twelvemonth. Unplug these items when you're finished with them, or better yet, apply a power strip.

Our other offenders are "wall warts" — a nose-wrinkling term for those chargers with oversized, boxy plugs — and other Ac adapters. In a national brandish of incomprehensible laziness, these power supplies are frequently left plugged in when disconnected from the gadget in question. It's as if you decided to cascade yourself some orange juice, filled upwards the glass, then just left the jug lying on its side, the summit off, contents spilling everywhere. Why, people, why?

My tidiness issues aside, it turns out there'south but 1 thing worse than leaving a charger plugged in with no device attached: leaving it plugged in and charging for too long. Now, T.K., we become to the center of your question, just we must travel along slightly divergent arteries to discuss your phone and computer.

According to our very thorough, very reliable friends at the Lawrence Berkeley National Laboratory, who measured several devices in each category, a cell-phone charger draws an average of three.68 watts when the phone is on and charging; ii.24 watts when it is on and charged; and 0.26 watts when it is merely hanging out in the socket. So put very merely, leaving your charged phone fastened to the charger uses 10 times the free energy that leaving the charger dangling would. None of this amounts to much on its ain; the Berkeley Lab people estimate that each watt they measured translates into roughly $1 per yr of energy expenses, and then nosotros're talking about $3-$four per charger, per yr. Only when you lot consider all the chargers in your firm, and then multiply it by the 115 1000000 or so households in the U.S., it adds up.

Your laptop follows a similar-simply-higher-stakes pattern, drawing an average of 44.28 watts when information technology is charging; 29.48 watts when it is charged; and four.42 watts when we let the charger dangle. Laptops become a fleck more complicated, because keeping them plugged in can actually be a good matter — it'due south more efficient to use that power to run the machine than to use it to charge a bombardment which then runs the machine. So if you're going to exist stationary for any length of time, consider keeping the car plugged in (be sure to cheque your manufacturer'southward recommendations, as they do vary). Also, ignore people who try to scare you about having to charge, discharge, and recharge your battery; today'due south lithium-ion models practise not demand such handholding (here are a few tips for making your Li-ion battery last).

T.G., if you're feeling forgetful when it comes to your chargers, I have a few ideas:

  • Create a central charging area for all the devices in your house, using a power strip (with a timer, even) to ensure that zip is left on longer than needed.
  • Bank check out culling chargers like wind-up or solar devices.
  • Buy a watt meter, which can be had for $20-$twoscore, to meet how much free energy you lot're using around the house, and how much it costs. (To give y'all a sense of scale, many users written report that dangling chargers utilize so little energy as to non register on these meters.)
  • When the fourth dimension comes to buy new electronics, wait for the Free energy Star label.

Frankly, I'm of two minds about whether we should all freak out about chargers. Standby ability use is responsible for an estimated 1 percent of global CO2 emissions, and every little bit certainly counts. But if y'all haven't taken bigger steps like insulating your firm or embracing public transportation, fretting over wall warts might non be the best use of your energy.

Juicily,
Umbra