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How to use
- Enter Standby watts per device.
- Enter Devices.
- Enter Standby hours/day.
- Enter Days.
- Enter Price per kWh.
- Calculate, then review power, price and period before comparing.
How it is calculated
kWh = standby watts × devices ÷1000 × hours × days
Example
Ten devices drawing 5 W standby for 20 hours daily over 30 days use 30 kWh and cost 5.4 at 0.18 per kWh.
Important notes
Some devices vary standby draw or enter deep sleep. Measuring with a plug-in power meter gives better accuracy than a nominal estimate.
Worked examples and interpreting results
| Case | Calculation | Result |
|---|---|---|
| Standby kWh | 5 × 10 ÷ 1000 × 20 × 30 | 30 |
| Cost | 30 × 0.18 | 5.4 |
Frequently asked questions
Should I assume 24 standby hours?
Only if devices are never actively used or disconnected; subtract active-use hours.
Is the result an actual utility bill?
No. It is a calculation from your usage, price and inputs; real tariffs, taxes and fixed fees may add other items.
How can I improve accuracy?
Use measured or device-specific power and usage plus the actual electricity price for the same period.