Whether you have an electric or gas heating system: Heating water requires a lot of energy and is quite expensive. That way you can easily save a lot in the bathroom.
Use cold water for brushing your teeth and washing your face.
Don’t take too hot showers. It’s not only bad for your skin, but also requires a lot of energy. Also, shorter showers are more energy efficient than longer ones.
Wash your clothes, if possible, at max. 40°. Generally speaking, the shorter and hotter your washing machine works, the higher the energy consumption.