How Much Energy Does My Phone Charger Use?

By Vernon Trollinger, February 9, 2016, Energy Efficiency

Saving energy (and money) is always easier when you know how much you’re using. But because many of our smaller appliances draw little amounts of power, we often discount how their combined impact contributes to your home’s energy usage. With our “How Much Energy Does This Appliance Use?” series, we”ll examine what’s watt to learn approximately how much they use. To help you understand very basic electrical consumption calculations, keep this simple equation in mind: Volts (V) x Amperes (I) = Watts (W). What you’ll discover is how just how these little conveniences can make big differences on your bill.

How Much Energy Does Your Phone Charger Use?

Both cordless landline phones and smartphones need to have their batteries charged. You might think a phone battery charger should be interchangeable because they’re battery powered, but they work differently, have vastly different power requirements, and affect your electrical usage differently as well.

Smartphone Chargers

How Much Energy Does This Appliance Use? - Your Phone Charger

No one wants to see this screen, since it means you can’t post that new sunset picture you just took to Instagram.

Smartphone chargers use 15 to 20 watts when they’re plugged in. Leave your charger plugged in for an hour, and that becomes 15 to 20 Watt-hours (Wh) of usage. For more than a decade, the power consumption has been roughly the same: 100 Volts AC (VAC) at .15 to .20 amps or about 15 to 20 watts. This is because chargers were developed to ultimately use the popular Universal Serial Bus connector (USB) to deliver 5 volts DC at 1 amp to the device to be charged.

For comparison, consider my household collection of USB chargers.  Both my old iPhone wall charger and my brand new charger pull about 100 VAC at .15 amps (15 watts) each. A ten-year-old charger from a flip-phone with a USB connector ate 100 VAC at .20 amps (20 Watts), and my son’s five-year-old smartphone charger also used 100 VAC at .15 amps (15 watts). Even flip-phone chargers from the year 2000 with those really annoying proprietary connectors pull 100 VAC between .15 and .20 amps and put out — yep, you guessed it — 5 volts DC at 1 amp.

While 15 to 20 watts can add up fast, the great thing about smartphone chargers is you don’t need to keep the charger plugged in. Once you’ve charged up your phone, you’re done for a few days. Plus because the USB connection offers more charging flexibility, you can charge your smartphone from your computer’s USB port or even from charging ports or adapters in your car.

How much does it cost? Depending on the manufacturer, charging a smartphones takes between 30 minutes and 2 hours. Let’s say at worst you’re using 20 watts for one-hour charging cycles twice a week. That’s 40 Watt hours (Wh). Multiply by 4 weeks, that’s 160 Wh/month or .16 kWh. If you are paying 10¢/kWh, charging your smartphone here costs about 1.6 ¢/month.

Cordless Land Line Phones

How Much Energy Does This Appliance Use? - Your Phone Charger

If you’re under 25, you might not know what this is – unless you love watching reruns of ’80s and ’90s sitcoms.

While smartphones chargers might consume more wattage per charge, cordless landline phones tend to use more electricity because their base stations are always on — no matter if the phone is being used or not. Both the AC adapters for handset chargers and bast stations will have input voltages between 100 to 120 VAC with amperages varying from .20 to .90 or even 1 full amp. Wattage will vary depending on whether the phone is in standby mode (some models use between .3 and .9 watts) charging a phone or if it is a base station transmitting to a hand set (up to 3 watts).

How much does it cost? Since cordless phones can consume an average daily usage of about 2.5 watts, they can eat up to 2kWh/month. That adds up to around 25¢/month.

Does your bill make you cry? Next up “How Much Energy Does This Appliance Use?“, we’ll try to pacify you with a look at baby monitor systems.

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About 

A native of Wyomissing Hills, PA, Vernon Trollinger studied writing and film at the University of Iowa, later earning his MA in writing there as well. Following a decade of digging in CRM archaeology, he now writes about green energy technology, home energy efficiency, DIY projects, the natural gas industry, and the electrical grid.

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