Galaxy S9 and 15W Qi wireless chargers: Does it actually charge faster?

This year, Samsung's Galaxy S9 series supports wireless charging. Same as last year, right? Except that there's new hardware inside the phones to wirelessly charge at up to 15 watts, which is twice the speed of most phones (and more than double that of the Galaxy S8).

Charging speed is the only thing keeping some people away from wireless chargers, assuming their phone supports the feature. Even with advancements in the Qi standard and new charging pads, they're still notably slower than wired charging. For Samsung's phones, the sure bet for the fastest charging has always been its own chargers — product reviews for third-party chargers all over the internet are littered with people citing various problems using X phone with Y charger.

Now that Samsung's phones technically support these new speeds, we wanted to see how that translates to real-world usage. Several manufacturers have debuted wireless chargers with 15W of output, a considerable jump over the 10 or 12W previously offered, and far more than Samsung's own chargers that top out at 9W. They're available from Ventev (opens in new tab), Griffin (opens in new tab), Belkin (opens in new tab) and Spigen (opens in new tab), to name a few. So I bought that Ventev model to see just how much faster it is than Samsung's own charger (opens in new tab).

It was a simple test setup: run a Galaxy S9+ down to 0%, then turn it back on while on a charger and see how long it took to reach 100%, measuring every 15 minutes. The tests were done with the phone in airplane mode, to rule out extraneous network activity impacting charge time. For a baseline, I also recorded the charging speed from the in-box Fast Charge wall charger.

The results were disappointing.

Even with a much higher wattage rating, the charging times were identical.

You can see that Ventev's wireless charger, running at a much higher 15W output, charged at a near-identical rate to Samsung's 9W wireless charger. Doing two more rounds of testing, including a run with the phone completely off, yielded the same results within a couple minutes. Both chargers also charged the phone at a very linear rate, about 10-11% per 15 minutes, no matter the charge of the battery; the only outlier being the final 5%, which was unsurprisingly slow. Total charge time was 2 hours 30 minutes, which aligned with the estimate provided on the GS9+'s lock screen — turns out those numbers are generally accurate.

Compare that to the wired charger, which charges at almost double that rate, 20% per 15 minutes, up to about 75% before slowing down. The wired charger gets from 0-50% 30 minutes faster than wireless, and 0-100% 50 minutes faster — a full charge happens in 1 hour 40 minutes.

Pick your wireless charger for its design, utility and price — not for its claimed higher output.

After collecting all of this data, it looks like Samsung has done us a favor by choosing to not emphasize the wattage ratings of its own chargers and instead simply standardizing to a brand like "Fast Charge." In this case, a purportedly higher-end and "faster" wireless charger didn't yield charging speeds that were faster in any way, yet the Ventev charger is about $55 (opens in new tab) — more expensive than the current listing for Samsung's latest charger (opens in new tab) and far more than other lower-wattage chargers.

Now it isn't all bad news. Knowing that you can go buy a third-party wireless charger that charges just as fast as Samsung's is great — and you get more options for designs, form factors and prices without giving up charging speed. And I don't feel Ventev (and all of the other companies listed above) is attempting to mislead anyone — it's simply trying to market its advantage in charging output ... even though as I've shown here, that doesn't translate into an advantage in charging speeds. It's possible the Galaxy S9 series will be updated to support 15W charging (Apple's iPhone 8 and X series was updated through software to increase wireless charging from 5W to 7.5W), and we've reached out to Samsung for details about this.

So after this testing, we know to pick your wireless charger for its design, utility and price — not necessarily its claimed higher output. And when in doubt, know that Samsung's own wireless chargers will provide the fastest speeds for a Samsung phone.

Andrew was an Executive Editor, U.S. at Android Central between 2012 and 2020.

22 Comments
  • Good old wall charger... works everytime. I do have a Seneo fast wireless charger on my desk at work but I'm usually not to concerned about the speed as it's going to be docked there the better part of the day.
  • i have unbranded fast wireless charger takes about 3 hours to charge
  • Just curious to know if another type of phone was tested on the same setup to determine if the 15w charger actually performs as intended?
  • Are there any other phones that support it? I haven't heard of any
  • Lg V30 is compatible with 15w wireless
  • Before seeing this comment, I came here to say the same thing.
  • Rarely use a wired charger any more. We have three Samsung wireless chargers around house. Its just easy. Its fast enough to top off middle of the day.
  • A more "scientific" approach should be taken in addition to "clock time." Connect an inline USB wattage meter between the wall outlet and the wireless charging pad. That will tell you how many watts are being delivered. One can be found in many outlets by searching "USB Safety Tester" It will also show the Volts, Amps, Wattage, Ah and Wh delivered since reset (there is a reset button like an odometer). You're welcome for the idea.
  • How will that work when the current isn't going through the USB port? Edit: never mind, you said between the wall and the charger.
  • If all else fails there's also using a Kill-A-Watt P3 that plugs inline with the mains.
  • How would that change anything here? The end result is all that matters to people — the 15W charger doesn't charge the phone any faster than the 9W charger. That would also simply tell you how much power's going from the wall plug to the charger, not how much is actually getting into the phone. Also, the 15W wireless charger doesn't use USB — it's a regular old barrel connector to the wall plug, so couldn't get an in-line USB meter on it.
  • I have the S7 edge. It's true that it's frustrating how much slower wireless charging is. It also seems to get slightly slower over time. Performance degradation in general is why I didn't go back to Samsung already. I have the flat Samsung fast charger and the stand one that came out with the S7. Are they both 9W, then? And the S7 supports up to 9W only? In general it feels like wireless charging is marketed in a complicated way that will confuse most consumers. Let's not forget we are more invested than most.
  • I really don't understand what a so called wireless charger does that my wired charger can't.
    I see the same wire but instead of a small USBC at the end there's a large pad.
    I like to use my phone while it's charging so along with the inconvenience of not charging quickly you also can't pick up your phone.
  • Try it with the V30. It supports 15W as well. AC only ever tries this stuff on Samsung phones.
  • Hey Andrew, I have not thoroughly researched wireless charging technology but isn't the charging speed also somehow dependent on the winding ratio of the induction coil receiver inside the phone? I say this because I think beyond a certain output threshold of the charger, you need a better receiver in order to increase the charging speed. This was potentially what was lacking in your experiment. I could be wrong but I think your phone's receiver could probably only output 1A or maybe 1.5A regardless of the output of the wireless charger. This is probably why you had the results you had. Anyways, just my two cents.
  • As mentioned in the article, the charger he chose is supposed to have 15W output, and the S9 is supposed to support 15W input. Near the end of the article, he mentioned perhaps it is limited by software.
  • Does the Ventev charger have cooling fans like the Samsung one? I only ask because two years ago I bought an Anker wireless charger that would heat up the phone (S7 at the time) like crazy to the point the phone would either stop charging or power off. Since then, I only purchase wireless chargers from Samsung for my S9 and my fiance's iPhone 8+.
  • Mine S9 is in a Incipio case and doesn't charge very well using the Samsung Fast Charge wireless charger - does the higher wattage overcome this?
  • Did you not read the article?
    The answer is a very clear "no".
  • Just re-read the article. Not once was a case mentioned. From the image, it appears the device has no case. The article shows that a caseless S9 doesn't charge any faster, but perhaps, with a case, the higher output of the charger may help the device charge quicker by overcoming the case's resistance.
  • It would really be interesting to know what the internal temperature is during charging. Wireless chargers are less efficient, so there is heat going somewhere. I suspect there would be an increase in battery temperature, which is a bad thing.
  • « Charging speed is the only thing keeping some people away from wireless chargers » Ut’s nlt the only reason. I stopped using wireless charging because my phone was getting hot, way more than with the wired charger. I think witeless charging hurts the battery more on the long term.