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

If you own a smartphone, chances are good that it serves some vital purposes in your life. It may be what wakes you up each morning, how you check traffic reports, how you navigate, how you take photos and video — even how you make phone calls. But do you ever wonder what it’s costing you to keep that technological powerhouse running? How much does it cost to charge a phone?

The answer is reassuring.

Don’t Stress Over Smartphone Power Consumption

It’s now the norm for American households to have no landline phone. According to 2016 data collected by the National Center for Health Statistics, 50.8 percent of American homes rely entirely on mobile phones for communication.

As more consumers leave landlines behind, they’ll also be getting rid of their cordless landline phones, which tend to consume about two kilowatt hours (kWh) per month. At a typical rate of about 12 cents per kWh, ditching those landline phones could save you just under a quarter per month per phone — not something most electricity customers will notice on their monthly bills.

But would you believe that smartphones use even less electricity?

How Many Watts Does It Take to Charge a Phone?

In spite of the fact that your smartphone does the work of dozens of gadgets, it doesn’t ask for much in terms of electricity. Forbes took a look at this issue in 2013 and found that if you fully drained and recharged an iPhone every day, it would cost you about two kWh per year — that’s less than a quarter for an entire year of smartphone convenience.

Smartphone batteries and chargers have changed a little since Forbes’ test, but not enough to make a noticeable dent in your monthly electric bill. The biggest smartphone batteries of a few years ago clocked in at 1,440 milliamp-hours (mAh), while today’s iPhone X holds almost twice that amount of energy with its 2,716 mAh battery.

And while it’s still fine to use standard five-watt USB charging adapters when time is no object, smartphone users who need super-fast charging can opt for “fast” chargers that draw up to 30 watts.

The higher iPhone charger wattage will consume more electricity in a shorter length of time, but compared to slower chargers, they’ll cost you about the same in the long run. The bigger difference maker is the size of your smartphone battery, but even the difference between a 1,440 mAh battery and a 2,716 mAh battery comes out to about a quarter per year.

The bottom line: smartphones run on pocket change.

How Many Watts Does a Phone Charger Use?

You may have heard that it’s wasteful to leave phone chargers plugged in all the time, but we have good news for you there, as well.

It’s true that a plugged-in charger draws electricity even when there’s no phone on the other end of the cable, and therefore the best practice is to keep them unplugged when not in use. But when it comes to your monthly bill, diligently unplugging these chargers won’t make much of a difference.

How-To Geek ran its own experiment to discover how much energy these gadget chargers can really waste. They used a Kill-A-Watt electricity meter to measure the energy consumption of a variety of common chargers, and discovered that no one charger used a detectable level of electricity. In the end, the experiment’s designers simultaneously connected six gadget chargers plus a power strip to achieve a measurable reading of .3 watts, which amounts to a little more than 30 cents per year. So even if you make a point of always unplugging your chargers when not in use, the savings potential comes out to a rounding error.

We should always be on the lookout for ways to conserve electricity — it’s good for our budgets, and it’s good for the planet. But our phones and chargers use such small amounts of energy that they really aren’t worth fussing over. Instead, it’s better to focus on reducing the energy consumption of big things like our air conditioners, furnaces, water heaters and kitchen and laundry appliances.