Phantom Load Calculator: What Standby Power Costs You

Phantom load, also called standby power or “vampire” power, is electricity used by devices that are switched off or not doing their main job. A TV waiting for its remote, a phone charger with nothing attached, a microwave clock and a router all count. Each one is small, but they run 24 hours a day, 365 days a year, so they add up.

How the calculation works

The calculator adds up the always-on wattage of your devices, turns it into kilowatt-hours (kWh) for a full year, and multiplies by your electricity price.

Total standby watts = number of devices × average standby watts per device
kWh per year        = total standby watts × 8,760 hours ÷ 1,000
Cost per year       = kWh per year × electricity price ($/kWh)

There are 8,760 hours in a 365-day year. Dividing by 1,000 turns watt-hours into kWh, the unit on your bill. Berkeley Lab gives the same rule in round numbers: one watt running all year is about 9 kWh.

The default electricity price is $0.18 per kWh, based on the US average residential price of 18.31 cents per kWh in July 2026 (EIA Electric Power Monthly, Table 5.6.A). Replace it with your own rate.

The main assumption is that every device draws the same average standby power all year. In real homes a few devices draw most of the standby power, and some switch between low-power modes.

Worked example

The default inputs describe a home with 25 plugged-in devices averaging 2 watts each, at $0.18 per kWh.

1. Total always-on load: 25 × 2 W = 50 watts.
2. Yearly energy: 50 W × 8,760 hours ÷ 1,000 = 438 kWh.
3. Yearly cost: 438 kWh × $0.18 = about $79 a year.

That is money spent on devices you are not actively using.

A second example

Say a California household has 40 newer devices on standby, averaging 1 watt each, and pays $0.34 per kWh. California’s average residential price was 33.61 cents per kWh in July 2026 (EIA, Table 5.6.A). The calculator returns a 40.0-watt load, 350 kWh a year and about $119 a year. Fewer watts per device, but a much higher rate, means a bigger bill.

Now try the low end: 25 devices at 0.5 watts each, the level Berkeley Lab says most products are now under, at $0.18 per kWh. The result is 12.5 watts, 110 kWh and about $20 a year. That gap shows why your measured wattage matters more than the device count.

What your result means

Treat the result as a size check, not an exact bill line.

• Under about $25 a year: your standby use is already modest. Unplugging more devices will save little. Spend your effort on bigger loads.
• $25 to $100 a year: worth an hour with a plug-in watt meter. Find the two or three devices that draw the most and put them on a switchable power strip.
• Over $100 a year: look for a hidden always-on load. Common culprits are older entertainment gear, extra refrigerators or freezers, recirculation pumps, aquarium or pet heaters, and spare TVs with set-top boxes.

To see what a single appliance costs when it is actually running, use the appliance energy cost calculator. To see how standby fits into a whole monthly bill, try the electric bill calculator.

Typical standby levels to compare against

Use this table to sanity-check the “average watts per device” you enter. The ranges come from Berkeley Lab’s descriptions, not from lab tests of specific models.

The kWh figures follow the formula above. Your real home will be a mix. One device drawing 15 watts adds more than 30 devices drawing half a watt.

What changes the answer where you live

Your electricity rate. This is the biggest swing factor. In July 2026, average residential prices ranged from about 12.72 cents per kWh in Louisiana to 48.00 cents in Hawaii (EIA, Table 5.6.A). The same 50-watt standby load costs about three to four times more in Hawaii than in Louisiana.

Time-of-use rates. If your utility charges more at certain hours, standby power is billed at every rate, because it never stops. Use your average all-in price per kWh: total bill divided by kWh used.

How many devices you own. Berkeley Lab notes that standby per product has fallen, but the number of products with standby has grown. A home with smart speakers, smart plugs, security cameras and several chargers can have many small loads.

Programs and help. There is no federal rebate for power strips or watt meters. Some utilities give away or lend energy-saving kits, and some public libraries lend watt meters. Ask your utility. If high bills are a strain, see our guide to help paying energy bills.

Common mistakes

• Using the nameplate wattage. The label shows maximum power when running, not standby power. Standby is usually a tiny fraction of it.
• Counting devices that are actually on. A router or refrigerator is working, not idle. Its power use belongs in the appliance calculator, not here.
• Assuming every device draws the same. A cable box and a phone charger are not alike. Measure the large ones separately.
• Using only the energy rate. Your bill has fixed charges and taxes. Use your all-in cost per kWh for a fair picture.
• Unplugging things that need power. Medical equipment, security systems, sump pumps, smoke alarms on plug-in power and devices that must install updates should stay on.
• Expecting big savings. Berkeley Lab says an aggressive effort can cut standby use by about 20 percent. Useful, but heating, cooling and water heating usually matter more. Our guide on how to lower your energy bill ranks the bigger moves.

Limits of this calculator

This tool uses one average standby wattage for all devices. It does not model devices that switch between sleep, network standby and off modes, or loads that change with the season. It assumes the device stays plugged in all 8,760 hours of the year and uses a single flat electricity price.

A home energy audit can find always-on loads you would not think to count, such as pumps, heaters and old appliances. This calculator gives an educational estimate, not a quote, a measurement or advice for your home. Measured watts and your own bill are always better than defaults.