We’ve all used splitters and power strips to plug multiple items into a single receptacle, and while this can overload the circuit or damage the receptacle, it doesn’t reduce the amount of current that each device draws. In other words, if your electrical system is healthy, it shouldn’t slow charging.

That’s the hunch of someone with a physics degree and years of doing electric wiring and writing about it, but hunches don’t cut it when your job is to get it right. So, I did my research and interviewed experts. In the process, I came across this answer from Google’s Gemini answer bot: “The available power is divided among all the connected items, resulting in a reduced current for each individual device.” In other words, according to Gemini, plugging multiple items into a receptacle does slow charging.

HOWEVER: Gemini’s answers can be genuinely helpful, but this is a good example of why you shouldn’t rely on them exclusively. In this case, the bot seems to be hallucinating. “Your phone doesn’t care if it’s sharing an outlet with a toaster, a lamp, and a TV,” says electrician Ryan Gregor in dissent. “It just pulls the power it needs.” Other experts I interviewed agreed.

Does Plugging Too Many Things Into an Outlet Cause Charging to Slow Down?

For Gemini’s assertion to be true, an electrical receptacle would have to be analogous to a faucet in a residential plumbing system. When you turn on more than one faucet at a time, the pressure at each one is reduced because the pipes that supply the faucets can carry only a limited amount of water. But that’s not how electrical systems actually work.

The pressure that forces electric current to flow is called voltage, and in a North American residential electric system, it’s constant at 120 volts (or 240 volts for larger appliances). Following the plumbing analogy, it would be more accurate to compare an electrical circuit to a water tank that is kept full by an external source and to think of receptacles as holes drilled in the bottom of the tank. Since the pressure is constant, the only factor that determines the amount of water that flows through each hole is the size of the hole. In electric terms, the “size of the hole” is the current draw of a device plugged into the receptacle.

“It doesn’t matter how many devices are plugged into an outlet,” says electrician and HVAC pro Sergey Nikolin. “The speed of charging depends on the power output of the charger and outlet.” If a phone charger draws three amps of current, it will draw that much regardless of what else is plugged into the receptacle, and the phone will always charge at the same rate.

However, there are a couple of important caveats, as Nikolin explains: “Let’s say you use a shared USB hub powered by a single outlet. Here you might notice slower charging.” That would be due to the internal circuitry of the hub, and it’s more likely to happen with a cheap one.

“Also,” continues Nikolin, “using one outlet for multiple devices can overload a circuit (and even trip a breaker!), or generate excess heat (which wears down wiring over time and often happens in old houses). An overloaded circuit, in turn, can cause voltage fluctuations, and if the voltage drops below what your charger needs, it can reduce charging speed. Excess heat from overloaded wiring can damage connections over time, leading to higher resistance in the circuit and this can cause inconsistent power delivery to your charger.”

What’s Causing My Slow Charging?

If your device is taking longer to charge than expected, any of the following could be responsible:

  • A faulty charging cable or a poor connection;
  • Dirt in the charging port;
  • Background apps draining power;
  • Software issues that require an update;
  • An old, degraded battery that can’t hold a charge;
  • The charger isn’t the right one for your device.

Only after you’ve addressed all these potential causes of slow charging does it make sense to suspect that a voltage drop at an overloaded receptacle is responsible. If it comes to that, it may be time to consult an electrician for an inspection and a possible upgrade.

About the Experts

  • Ryan Gregor has over a decade of experience in the electrical field. He is the Owner and Head Electrician of Australia-based RCG Electrical.
  • Sergey Nikolin is the President of Product Air Heating & Cooling LLC, based in Marysville, WA. He has extensive experience in HVAC, indoor air quality, and electrical systems.

Sources

Author
Chris Deziel
Chris Deziel is a freelance service journalist who worked in landscaping and home improvement for more than thirty years. He has published over 10,000 how-to and expository pieces on home improvement and nature topics since he began writing in 2010. Deziel lives and works in an off-grid home in California where he enjoys recording original music an...
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Chris Deziel