Saving energy > Laundry

Wash with cold water whenever possible.
Wash and dry full loads to maximize efficiency.
Don't overload dryers.
Overloaded dryers use more energy, cause clothes to wrinkle so they may need to be ironed, and wears out clothes more quickly.
Use suds savers and front-loading washers for maximum efficiency.
Always adjust the water level to fit load size. Overloaded washers don't clean clothes as effectively so they even may need to be rewashed.
Clean the lint filter after each drying cycle to maintain dryer efficiency.
Spin-dry your clothes (on a highspin speed) to remove as much water as possible before you put them in the dryer.