How can I save energy when using a notebook?
I'm using a notebook as my only computer and I'm wondering how I might save the most energy (in terms of my electricity bill).
Will it use less energy overall to only plug it in if the battery is low and unplug it as soon as the battery is loaded? Or is it better to leave it plugged in until I'm done using it?
It's insignificant. Find better ways to save energy.
Your typical laptop consumes less electricity than one average light bulb.
This is a brilliant case of being penny-wise, pound foolish.
Laptop = 15-60 watts. Light bulb = 60-150 watts Fridge = 200-700 watts Dishwasher = 3500 watts Clothes dryer = 4500 watts ...
Are you planning to turn off your fridge every time it's cold enough and turn it back on just in time to avoid spoiling your food?
Energy saving should be an analytical activity. First, identify WHERE most of your energy footprint comes from, THEN figure out ways to reduce it. Don't fall for feel good, knee jerk measures.
Edit: Following your comment about electricity prices in Germany, here are some REAL numbers for you to think with:
Assuming 4 hours per day, 365 days per year, with a laptop consuming 50 Watts, you are using 76 kWh per year.
According to https://secure.wikimedia.org/wikipedia/en/wiki/Electricity_pricing:
1kWh = $0.306 (Germany - 2009).
76 x 0.306 = $22 per year.
If, through great efforts on your part, you saved 30% of your laptop energy consumption, you would reduce your yearly electricity bill by $7.
Do you really feel it is worth it?
To answer your actual question: discharging and recharging the battery, all other things being equal, will use more power than just being plugged in. Some energy is lost in the actual battery-discharge and battery-charge processes themselves, in addition to whatever you're actually using to do stuff on the laptop.
Other answers give good advice about how to actually lower your energy use.
- Turn the screen brightness down.
- Set the computer to automatically sleep/hibernate when idle (I have mine set to sleep in 5 minutes of idle time).
- Enable power-saving features of the CPU, e.g. Intel SpeedStep.
- Use smaller computer, a 11-inch Atom notebook uses less power than a 17-inch monster.
- If you need powerful graphics (e.g. for games), buy a notebook with dual VGA card, where one of the card is small power-saving card and the other is performance card. If you don't need powerful graphic, then don't buy a monster VGA card.
- SSD is more power friendly than a Harddisk, but they are also a bit more expensive.
- Spin down the harddisk, when not used.
- Avoid using peripherals, e.g. mouse, external keyboard, printers, etc all consume power. However, if using a mouse or external keyboard means you can finish a task in 1 minute instead of 10 then don't shy away from using them.
- Wifi, Bluetooth, and other wireless consumes power, disable them when you're not using them.
Type "cmd" on your "search for programs and files" and run the following command: powercfg -energy
After 60 seconds the program will create a html file that describes the possibilities to save battery consumptions and consequently energy.