Standby power is the electricity used when a device is idle but still connected. One device may draw little, yet several always-on devices can create a measurable annual cost.
Formula
Annual kWh = standby watts ÷ 1,000 × 24 × 365
Multiply annual kWh by the applicable tariff to estimate cost.
Worked example
Ten devices average 5 W each, for a combined 50 W or 0.05 kW. Annual energy is 0.05 × 24 × 365 = 438 kWh. At ₹8 per kWh, estimated annual cost is ₹3,504.
Measure before replacing
Nameplate ratings may not show standby consumption. A compatible plug-in meter provides better evidence. Devices with clocks, remote control, network connectivity, or instant-on modes are common candidates.
Use the Unit Converter for watts and kilowatts and the Percentage Calculator to compare before-and-after use.
Reduce waste safely
- Use switched power strips for suitable devices.
- Enable sleep and power-management settings.
- Do not disconnect safety, medical, network, or update-dependent equipment without checking requirements.
- Measure high-draw devices first.
Frequently asked questions
Do chargers use power when not charging?
Some draw a small amount; measure the specific charger if the decision matters.
Should I use the average or marginal tariff?
Use the tariff applicable to the additional kWh, including time-of-use or slab effects.
Will switching everything off save the full estimate?
Only if those devices truly stop drawing power and the change does not create other costs or risks.
Prioritise devices by annual energy
One 20 W always-on device uses about 175.2 kWh per year, equal to twenty 1 W devices combined. Measure or estimate watts first, then rank devices by annual kWh and ease of switching.
Some equipment needs continuous power for connectivity, recording, safety or updates. Use built-in low-power settings where disconnection is unsuitable. Compare measured baseline and follow-up use over similar periods and document which devices were included.