When my laptop is running out of battery, i go and charge it while on the laptop. And when it goes to full battery or close to it, many times i get lazy and unplug the charger from my laptop but I don’t unplug it from the outlet.
I still see the green charging light on it when its only plugged to the outlet.
I assume I am still using electricity because its connected to the outlet and shows green but it uses very little energy as oppose to when its connected to the laptop and charging?
Yes, you are using energy, but it’s not very much. For Energy Star certified chargers, it has to be under 1W. Most are even better than that.
Chargers are like most other electronics nowadays; they never really completely turn off unless they have an actual on/off switch (not a pushbutton); power consumption can be as much as 5 watts or so if it doesn’t have an Energy Star rating; the strictest ratings increasingly mandatory) reduce this to 10s-100s of mW. An easy test to see whether it is one of the “bad” ones (typically, the older it is, the more standby power due to less attention to efficiency) is to feel it after it hasn’t been loaded for a while, it will feel warm if it is drawing a significant amount of power. Also, for perspective, a 1 watt load will use 8.766 kWh per year (1 watt x 24 hours/day x 365.24 days/year), or about a dollar at common rates.