Now then chaps, I know a little bit about this refrigeration stuff but I just can't seem to "Get" electronic expansion valves!

We squirt liquid through a hole, and the reduction in pressure allows droplets to readily evaporate, providing our refrigeration effect. If the evaporator loading increases, we make the hole bigger and if it falls we close the hole up a bit, in order to regulate refrigerant flow and maintain our superheat.

How can it make our system more energy efficient opening or closing the valve (making the hole bigger or smaller) using an electronic stepper motor instead of just the usual pressure variation across a diaphragm?

The general perception seems to be that EEV will somehow work with reduced high side pressure, thereby achieving savings in compressor power input. I don't believe this to be correct, because after all an EEV is still just a hole as far as the refrigerant is concerned!

I am aware that EEV are much more "One size fits all" in terms of differing capacities and refrigerants, and can also obviate the requirement for a seperate solenoid valve, but can't really see these factors alone justifying the increased complexity.

Hopefully I am missing something profound, which will no doubt be revealed shortly?