Smart Plug Standby Power Use | Calculate Real Cost and Savings

By Marlo Strydom

The Short Answer: Yes

If you are wondering do smart plugs use electricity when not in use, the answer is yes. They require a small amount of power to stay connected to your WiFi network. However, the cost is minimal compared to the savings.

You want to save money on your electricity bill, so you invested in smart plugs. But then a logic check hits you: if the plug itself is electronic, surely it consumes power too?

I grabbed my energy meter to find the exact numbers. This guide breaks down exactly how much electricity smart plugs use on standby, how it affects your bill, and why the math still works in your favor.

In This Guide

  1. Why Do Smart Plugs Use Power When Off?
  2. My Test Results: Standby Power by Brand
  3. The Math: Cost to Run vs. Savings
  4. The Real Enemy: Vampire Power
  5. Comparison: Smart Plugs vs. Standard Devices
  6. 3 Tips to Maximize Savings
  7. FAQ

1. Why Do Smart Plugs Use Power When Off?

It helps to think of a smart plug not as a simple switch, but as a tiny computer. Even when you tell Google Assistant to "turn off the lamp" the smart plug itself must remain awake.

It draws what is known as standby power (or vampire power) for three specific reasons:

  • WiFi Connectivity: The internal radio must stay powered to maintain a connection to your router. Without this, it couldn't receive the "On" command from your phone.
  • AC/DC Conversion: The plug contains a transformer to convert your wall's high voltage (120V/240V) down to the low voltage needed for its internal chip.
  • LED Indicators: Most plugs have a small LED status light that draws a negligible, but measurable, amount of power.

2. My Test Results: Standby Power by Brand

Not all smart plugs are created equal. I used a Kill-A-Watt usage monitor to test several popular models to see how much electricity they actually draw when the connected device is turned off.

Here is what the data shows regarding smart plug energy consumption:

Plug Type Connection Standby Power Approx. Yearly Cost*
Standard WiFi Plug
(e.g., TP-Link Kasa, Wyze)		 WiFi (2.4GHz) 1.0 - 1.5 Watts $1.20 - $1.80
Energy Monitoring Plug
(e.g., Shelly, Emporia)		 WiFi 1.5 - 2.0 Watts $1.80 - $2.40
Hub-Based Plug
(e.g., Zigbee/Z-Wave)		 Mesh Network 0.3 - 0.8 Watts $0.36 - $0.96
Old Mechanical Timer Analog 1.0 - 2.0 Watts $1.20 - $2.40
*Calculated at the US national average of roughly $0.14 per kWh.

Key Insight: Zigbee and Z-Wave plugs use significantly less power (under 1 Watt) because they don't communicate directly with your power-hungry WiFi router, but rather with a localized hub.

3. The Math: Cost to Run vs. Savings

The biggest concern people have is whether the smart plug costs more to run than the savings it generates. Let's run the calculation.

The Cost of the Plug

If a standard smart plug uses 1.5 Watts continuously:

  • 1.5W x 24 hours = 36 Watt-hours per day
  • 36Wh x 365 days = 13,140Wh (or 13.14 kWh) per year
  • 13.14 kWh x $0.14 = $1.84 per year to run the plug.

The Savings (The Breakeven Point)

To break even, the smart plug only needs to save you $1.84 worth of electricity per year.

If you use a smart plug to turn off a Game Console that consumes 10 Watts in "Instant On" mode for just 8 hours a night:

  • Savings: 10W x 8 hours = 80Wh saved per day
  • Yearly: 29,200Wh (29.2 kWh) saved
  • Value: 29.2 kWh x $0.14 = $4.08 saved per year.

Verdict: Even in this conservative example, the plug pays for its own energy usage twice over. If you control a more power-hungry device, like a cable box or an older TV, the savings can be 10x to 20x the cost of the plug.

4. The Real Enemy: Vampire Power

Understanding phantom power (also called vampire power) helps explain why smart plugs are a net positive for your wallet. This is the power devices use when they are "off" but plugged in.

According to the Lawrence Berkeley National Laboratory, the average home loses significant energy to these devices. A smart plug acts as a physical barrier, cutting that power draw to zero (except for the plug's own tiny 1W draw).

Typical "Off" Power Draw of Common Devices

  • Cable Box / DVR: 25 - 45 Watts (Costs ~$40/year just to sit there!)
  • Desktop Computer (Sleep): 5 - 10 Watts
  • Modern Soundbar: 3 - 8 Watts
  • Smart TV (Listening Mode): 0.5 - 3 Watts

Using a smart plug on a Cable Box effectively trades a 30 Watt draw for a 1 Watt draw. That is a massive efficiency win.

5. Comparison: Smart Plugs vs. Standard Devices

To put the electricity usage of a smart plug into perspective, let's compare it to other always-on devices in your home.

  • Smart Plug (Idle): ~1 Watt
  • Microwave (Clock Display): ~4 Watts
  • WiFi Router: ~6 to 15 Watts
  • Phone Charger (No phone attached): ~0.1 to 0.5 Watts

While smart plugs do use electricity when not in use, they are incredibly efficient compared to almost anything else plugged into your walls.

6. 3 Tips to Maximize Savings

Since we know the plug costs about $2 a year to run, you want to ensure it is controlling a device that wastes at least that much. Here is how to optimize your setup:

  1. Target "Old" Tech: Older TVs, stereos, and game consoles from previous generations are notorious energy hogs. Prioritize smart plugs for these items.
  2. Skip Low-Power Items: Don't use a smart plug solely for a single LED lamp or a phone charger. The plug itself might use more power than the lamp would when off. Use smart plugs for groups of devices (via a power strip).
  3. Use Scheduling: Ensure the plug actually turns off. If you leave the smart plug "On" 24/7, you are adding the plug's 1W load on top of your device's load, which increases your bill. Automation is key.

The Bottom Line

Do smart plugs use electricity when not in use? Yes, about 1 Watt.
Should you worry about it? No.

The ability to kill power to high-consumption devices like entertainment centers and heaters far outweighs the negligible cost of running the smart plug itself. It remains one of the most cost-effective ways to modernize your home's energy efficiency.

Frequently Asked Questions

Do smart plugs increase your electric bill?

In most cases, no. While they add a tiny load (approx $2/year), they lower your bill by turning off power-hungry devices that would otherwise cost $20-$50/year in standby fees.

Should I unplug smart plugs when not in use?

No. Unplugging them disconnects them from your WiFi, meaning you lose all automation and remote control capabilities. The convenience and energy management features require them to stay plugged in.

Which smart plug uses the least electricity?

Generally, plugs that use Zigbee or Z-Wave protocols (like Philips Hue or Samsung SmartThings plugs) use less standby power than direct WiFi plugs, as they don't need to broadcast a high-power WiFi signal constantly.

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