Most of us leave the computer on during the day while we walk away from the computer for a few hours. Whether it’s laptop or desktop. It just makes more sense to leave it on since it’ll go to sleep by itself anyway. But according to a study done by the US department of energy, it actually saves more if you turn it off while you’re away. We all know that there is a small surge in energy when a computer starts up, but the small amount of energy is still less than the energy used when a computer is running for long periods of time. So the better choice is to turn it off.
It’s recommended that turning off the monitor if you’re away for more than 20 minutes, and both the monitor and computer off if you are away for more than 2 hours.
The other saving comes from cooling off the temperature in the house. Whether desktop or laptop do tend to heat up. But turning on and off your computer can be a hassle. So the best way is to leave it to hibernate which only uses 70% less of its electricity.
Also never use screen savers. Because it uses even more energy. The good news is that modern LCD color monitors do not need screen savers at all.
Source: EERE. U.S. Department of Energy