Plugging devices into power outlets to charge consumes energy even when the device is fully charged or not in use. This practice is common but inefficient, contributing to unnecessary electricity waste. Many modern devices, such as smartphones, laptops, and chargers, draw power continuously when plugged in, a phenomenon known as "vampire power" or "standby power." While the energy draw per individual device is often low, collectively it can significantly increase household electricity bills and environmental impact.

The inefficiency stems from two factors: static power consumption and lack of energy-saving mechanisms. For example, a typical USB charger consumes 0.1–0.5 watts when plugged in but not in use, according to the U.S. Department of Energy. Over a year, this equates to 43–182 kilowatt-hours of wasted energy per charger, costing $4–$17 annually at average electricity rates. A 2021 study by the Lawrence Berkeley National Laboratory found that U.S. households waste approximately $10 billion yearly on vampire power, with small electronics accounting for 5–10% of total residential electricity use. Additionally, fast-charging technologies like USB-C and wireless charging often operate at higher power levels, exacerbating energy loss. To mitigate this, experts recommend using smart power strips that cut off standby power or unplugging devices when fully charged. The Environmental Protection Agency estimates such measures could reduce household energy consumption by 10–15%, saving households $100–$200 annually.