Smart Plugs and Phantom Load: What You Can Actually Save
How much electricity standby devices really use, which ones are worth putting on a smart plug, and why the savings are smaller than most articles suggest.
- The formula is watts ÷ 1,000 × 8,760 × your rate; LBNL puts standby at roughly 5–10% of residential electricity, about $240 a year for an average household.
- Most of that standby load sits in devices you shouldn't switch off, so the recoverable share is far smaller than the headline number.
- A smart plug draws its own standby power continuously, which can cancel out the saving on a low-draw device.
- Measure before buying: a 0.5W device costs about 81¢ a year — not worth a $15 smart plug on its own.
- Groups of devices, like an entertainment cluster or a desktop setup, are worth putting on a smart plug; routers, DVRs and refrigerators are not.
On this page
Standby load is the easiest energy-saving story to tell and one of the easiest to overstate. It is genuinely worth addressing — just not first, not everywhere, and not before you have measured something.
What standby load actually is
Devices that appear off often are not: they are waiting for a remote, keeping a clock, holding a network connection, or charging an internal battery. LBNL's working definition is broad — almost any product with an external power supply, an internal battery, a remote control, a continuous display, or a permanent network connection draws power around the clock.
The scale is larger than most people expect and smaller than most people can act on. LBNL puts standby at roughly 5–10% of residential electricity in developed countries, and more than 1,300 kWh a year for an average U.S. household. At 18.44¢/kWh that is about $240 a year. The catch is in the next section.
Standby is not the same as recoverable
That $240 covers every device in the house that draws power while idle. A large share of it sits in things that must stay powered — the router, the refrigerator, smoke alarms, anything with a scheduled task — or in devices whose individual draw is too small for any intervention to repay itself. Treat the national figure as the size of the category, not the size of your opportunity.
The formula
Annual standby cost = average standby watts ÷ 1,000 × 8,760 hours × your rate. The 8,760 is a full year, because that is what continuous means.
How to measure standby properly
- Plug the meter directly into the wall, then the device into the meter. Check the meter's amp rating covers the device's peak draw, not just its standby draw.
- Put the device into the state you actually want to measure — genuinely idle, screen off, not mid-update.
- Read cumulative kilowatt-hours, not instantaneous watts, over at least 24 hours. Many devices are intermittent in standby: they wake to sync, download an update, or run a defrost cycle, and a spot reading catches none of that.
- Divide the kWh by the hours measured to get an average wattage, then apply the annual formula above.
- Measure the smart plug on its own the same way, or take the manufacturer's published figure, and subtract it.
- Compare the net annual saving against the price of the plug before buying more of them.
Where a smart plug earns its place
- An entertainment cluster — television, console, soundbar, streaming box — idle overnight and through the working day, all on one plug.
- A desktop workstation with monitors, dock, printer, and speakers, switched as a group.
- Garage or workshop equipment used a few times a month.
- Seasonal loads that otherwise sit powered year-round.
Where it doesn't work
| Device | Why not |
|---|---|
| Phone and laptop chargers | Modern chargers draw very little when idle; the plug may use as much or more |
| Router and modem | Cutting power drops the network and recovery takes minutes |
| DVR and set-top boxes | Scheduled recordings, guide updates and firmware patches all fail |
| Refrigerators and freezers | Never — this is a running load, not standby, and cutting it spoils food |
| Smart speakers and security devices | Cutting them defeats the function you bought them for |
| Anything with a clock you rely on | You will reset it repeatedly and then stop bothering |
| Devices that update overnight | An interrupted firmware update can leave the device unusable |
What to do next
Borrow or buy a plug-in meter and check five suspects over 24 hours each: the TV area, the computer setup, the garage, the counter appliances, and anything with a permanent standby light. Apply the annual formula to what you measure, subtract the plug's own draw, and buy plugs only where the arithmetic clears the price. Then spend the rest of your attention on heating, cooling and hot water, where the numbers are an order of magnitude larger.
Sources
- Standby Power — frequently asked questions (share of residential electricity, kWh per household) — Lawrence Berkeley National Laboratory. Consulted August 1, 2026.
- Electric Power Monthly, Table 5.6.A — average residential price by state — U.S. Energy Information Administration. Consulted August 1, 2026.
- Energy Saver: Save Energy, Save Money — U.S. Department of Energy. Consulted July 22, 2026.
- Residential Energy Consumption Survey (RECS) — U.S. Energy Information Administration. Consulted July 22, 2026.
Frequently asked questions
How much does phantom load cost per year?
LBNL estimates standby at roughly 5–10% of residential electricity, and more than 1,300 kWh a year for an average U.S. household — around $240 at 18.44¢/kWh. That is the total across every device, most of which you should not or cannot switch off. The share a smart plug can actually recover is much smaller.
How do I measure a device's standby draw?
Put a plug-in energy meter between the outlet and the device, leave the device in its normal idle state, and read the cumulative kilowatt-hours over 24 hours or more rather than the instantaneous watts. Many devices are not steady in standby — they wake to update, sync, or run a compressor — so a single spot reading of watts will mislead you.
How small is too small to bother with?
Run the number before deciding. A device drawing 0.5W continuously costs about 81¢ a year at 18.44¢/kWh. A smart plug costing $15 and drawing 1W of its own would never repay that — it would increase your consumption. The threshold worth acting on is usually a cluster, not a single device.
Which devices are worth putting on a smart plug?
Ones that are genuinely idle for long stretches and draw meaningfully more than a trickle: an entertainment cluster, a desktop setup with monitors and peripherals, garage or workshop equipment, and seasonal items. Groups beat individual devices, because one plug's own draw is then spread across several.
Do smart plugs use electricity themselves?
Yes, continuously, to hold a Wi-Fi connection. That draw is subtracted from whatever the plug saves, and on a low-draw device it can cancel the benefit entirely. Measure the plug itself if the manufacturer does not publish the figure.