It's generally accepted that Phase change cooling is more efficient that TEC cooling. However this is not always true.

I headed down to my local Air con shop to get some efficiency numbers on Phase change units. The smallest unit they sold used 950watts of electricity while providing 3,200 watts of cooling. That means for every 1 watt used 3.68 watts of heat was moved.

I will now compare this to TEC cooling. A 172watt TEC running at Umax (max volts 24.6) with an ambient temp of 26.85 uses 361watts of electricity while providing 172watts of cooling. That means for every 1 watt used 0.47 watts of heat is moved.

However since a TEC becomes more efficient as you lower its input voltage relative to Umax the same TEC running at 20% (4.92V) of Umax can achieve 83 watts of cooling while using 14.47 watts of electricity. That’s 5.73 watts of cooling for ever 1 watt used !

Here's a picture of a 172watt TECs efficiently relative to input voltage.

So depending on how you implement your TEC cooling system it may or my not be more efficient than Phase change cooling.