I have to drop 14.5 ~ 12V to 5V. Using 7805 will dissipate much heat. So,using below circuit will ease 7805 to drop less voltage and will generate less heat.
Using 7.2V 1W zener and 100 ohm 1W resistance :
What are the negative impact of adding zener-resistor combination at input stage of the circuit?
Will it add any efficiency in circuit. I have read that the 7805 are already replacement for zener-resistor combination, but I have seen people using these at input stage of 7805.