Hot Water Cylinder Timer

Hey Chc people. Has anyone recently installed a HWC timer so it only powers on and heat the water at certain hours ? I am with Contact and get free power 9pm-12am everyday. I was thinking if the time can be installed and it only heats water up during that time. I live alone and do morning shower before work and the evening shower is at the gym.

Its a bloody old cyclinder. For the timer, do i need to get in touch with electricians etc, anyone can chime on what cost will be like and million dollar question. Is 3hrs enought to heat water for one shower ?