A Computer's sleep mode is okay for overnight.
Actually, sleep mode still uses a significant amount of energy. Both the computer and the monitor are drawing power to keep themselves in a suspended mode, ready to wake up the second you want to use them again. In fact, they could be sucking up as much as a combined 12 watts while you're in bed dreaming of a lower energy bill.
Any time a computer is not going to be in use for a long period of time, be sure it is turned off. There are a variety of software programs that help you out with this. You can set your computer to save energy, and even to shut down at appointed times without having to be there to flip the switch.
Appliances don't use power while in stand-by mode.
Photovoltaic panels will never generate more energy than was used in their manuf...
Showering uses less energy than taking a bath.
Windmills kill a significant number of birds, bats, and moths.
Turning the heat down at night doesn't save any energy because you just have to ...