Why does my bill not fall by exactly this amount?

The estimate assumes the entered wattage, schedule, and rate stay constant. Real devices change modes, electricity prices can include tiers or time-of-use rates, and fixed bill charges do not fall when consumption falls.

Home Energy Vampire Power Cost Calculator

Estimate how much electricity devices use while off, idle, or in standby. Add measured or estimated standby loads to see daily, monthly, annual, and avoidable costs. Inputs stay in your browser.

What one watt of standby power costs

A continuous 1-watt load uses about 8.77 kWh per year. Multiply that by your electricity rate: at an illustrative rate of $0.20/kWh, it costs about $1.75 per year. Ten continuous standby watts use about 87.7 kWh and cost about $17.53 per year at that same rate.

Power to energyWatts × standby hours ÷ 1,000 = kWh.

Energy to costkWh × your variable electricity rate = cost.

Best inputMeasure low-watt standby draw with a suitable plug-in electricity meter.

Rates and standby devices

1. Cost and impact assumptions

Currency Display only; no exchange-rate conversion. Electricity rate per kWh Use the variable energy rate from your bill. Avoidable standby share (%) Share that could safely be switched off. Grid emissions (kg CO₂/kWh) Optional editable planning factor; use local data.

2. Devices in standby

Add an editable example Examples are planning inputs, not product ratings.

Results update as inputs change.

Estimated standby cost

Current annual cost — Enter valid device values to calculate.

Core methodStandby watts × standby time ÷ 1,000

ScheduleHours per day × connected days per year

Result scopeElectricity use, cost, and optional operational CO₂

PrivacyNo input upload or storage

How the vampire power calculation works

Each row describes one device type during its off, idle, sleep, or standby state. The calculator treats the entered watts as constant during the entered standby hours and adds all device rows. Full precision is retained internally; displayed values are rounded.

Device kWh/year = quantity × standby watts × standby hours/day × connected days/year ÷ 1,000 Annual standby cost = total standby kWh/year × electricity rate per kWh Avoidable kWh and cost = current total × avoidable standby share Operational CO₂/year = total standby kWh/year × grid kg CO₂/kWh

Do not count active use twice: enter only hours spent in the standby state represented by the wattage. If a television runs for 4 hours each day and sits in standby for 20, enter 20 standby hours—not 24.

Get a more useful estimate

Measure the low-power state

Nameplate ratings commonly describe maximum input, not standby draw. Use a meter that can resolve small loads and measure long enough to catch cycling, updates, and sleep transitions.

Use your marginal rate

Enter the part of the bill charged per kWh. Fixed customer charges remain even if standby consumption falls. For time-of-use plans, use a weighted rate for the hours represented.

Separate necessary loads

Avoid switching off equipment that supports security, medical needs, freeze protection, appliance safety, networking, scheduled recordings, or required remote access.

Count the control device

A smart plug or remote-controlled strip may consume power itself. Compare its standby draw with the load it can eliminate; a simple switched strip may suit some groups of devices.

Assumptions and limitations

The built-in device values and $0.20/kWh rate are editable examples, not national averages or model-specific claims. Standby consumption can change with device settings, network state, battery charging, software updates, temperature, and age. For best results, replace every example with a measurement and use the rate and emissions factor applicable to your household.

Monthly values equal annual values divided by 12, and ten-year cost assumes the same device use and electricity rate for the full period. Results exclude active energy, power-strip or smart-plug consumption unless listed, rate escalation, taxes, fixed charges, manufacturing impacts, and disposal. The CO₂ result is an operational planning estimate, not a life-cycle or regulated inventory.

Vampire power cost FAQ

What is vampire power?

Vampire power, also called standby power, is electricity used while a device is connected but not performing its main function. Displays, remote-control receivers, network connections, sensors, and power supplies can all draw standby power.

How do I calculate standby electricity cost?

Multiply standby watts by standby hours per day, connected days per year, and device quantity. Divide by 1,000 to get annual kWh, then multiply by the electricity rate.

Should I use the wattage printed on the device?

Usually not. A nameplate often states maximum or active power. Measure the actual standby state with a suitable plug-in electricity meter when possible.

Is all standby energy avoidable?

No. Routers, security and medical equipment, appliance safety controls, scheduled recordings, clocks, and remotely accessed devices may need continuous power. Only include a load in the avoidable share when it can safely be switched off.

Does a switched-off smart plug use electricity?

Many smart plugs still draw power for their radio and controls. Add the plug as its own row or subtract its measured use from the expected savings.

Why might my bill change by less than the estimate?

Fixed charges do not fall with kWh, devices can move among several power states, and actual rates may be tiered or time-dependent. This calculator holds the entered wattage, schedule, and rate constant.

Are my device and rate inputs tracked?

No. Calculations, copied text, and CSV creation occur locally in your browser. The tool does not upload or store these inputs.