The resistor voltage divider seems to have the price advantage and higher voltage and power Zener diodes are not as common but... From an energy standpoint, the low Zf forward impedance seems to give the Zener the nod from an energy loss standpoint. Am I missing something here?

 

Am I missing something here?

If it costs a nickel more to do the job right, I'd spend the money.

 

With resistor voltage divider, the output voltage is not constant. The voltage will drop as more current is supplied to the load.

With a zener regulated circuit, the voltage is relatively constant (depending on the characteristics of the zener) from zero load current up to the maximum designed current. The power consumed is the same regardless of the load current, i.e. power dissipated is the supply voltage x max current.

 

If the supply voltage and the load current are both constant, then a voltage divider works and requires only one resistor. We use this to power LEDs often.

 

A resistive voltage divider is not used as a voltage "power source" unless the load current is negligible compared to the divider current.