Device Power Calculator
Choose from common device presets or enter custom wattage. See daily, monthly and yearly electricity costs per device. Compare multiple devices. Runs locally.
Updated July 11, 2026
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Electricity Rate
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Formula Reference
Daily energy (kWh) = Watts (W) x Hours per day / 1000
Daily cost = Daily energy (kWh) x Rate ($/kWh)
Monthly cost = Daily cost x 30 days
Yearly cost = Daily cost x 365 days
Standby cost = Standby W / 1000 x Standby hours x 365 x Rate
How to use
- 1
Select a device preset or enter custom wattage.
- 2
Set daily usage hours.
- 3
See cost estimates and add more devices.
How it works
Active vs. standby power
Most devices draw power in two states: active (in use) and standby (plugged in but off or idle). A modern desktop might pull 200 W under load but still draw 1–3 W in sleep — a NAS or smart TV may pull 10–20 W of "vampire" draw around the clock.
This is why the calculator models both states separately and sums them. On devices that run 24/7 (routers, NAS, servers, always-on desktops), standby baselines can dominate the annual cost — far more than the bursts of peak usage.
To measure a single device precisely, use a plug-in wattmeter (e.g. Kill A Watt) or check the manufacturer's spec sheet for typical (not peak) consumption.
- Standby ("vampire") draw adds up: 5 W × 24h × 365d ≈ 44 kWh/year per device
- Nameplate wattage is a regulatory maximum — typical use is often 30–60% of it
- Always-on devices (NAS, router) matter more than rarely-used ones (printer)
How this is calculated
- Formula:
- Daily energy (kWh) = (active power (W) × active hours + standby power (W) × standby hours) ÷ 1000. Annual cost = daily kWh × 365.25 × rate ($/kWh).
- Applies to:
- Reference rates; confirm with your local utility and tariff.
Device power draw varies widely with model, age, settings, and actual usage — listed wattages are usually nameplate maxima, not average consumption. Electricity rates vary by provider, time of use (peak/off-peak), tier, and currency. Results are estimates for comparison only; not financial advice. Verify figures on your device label or manual and your utility bill.