# Thermoelectric cooler's Qmax cites maximum heat transfer — how is it so close to rated wattage considering TEC's low efficiency?

Some background regarding my question:

I'm thinking if making some sort of TEC-based ice cream maker. Considering the combined specific heat capacities, I calculated (possibly incorrectly) the value in watt hours to be slightly less than 8wh to cool 600 grams of ice cream mix (would be 1 batch) 14 degrees from (a refrigerator-cooled) 4 degrees celsius to -10 degrees celsius.

So the TEC needs to be able to reach that low temperature, and for time's sake it (or the combined set of them) needs to pump heat energy at around 24 watts so it won't take more than 20 minutes to reach a solid-ish ice cream.

I bought once (for a different purpose) a couple of cheap TEC from a Chinese vendor and they seemed to perform lousily and were of inconsistent quality, so I tried looking for offerings from known TEC manufacturers.

The spec sheet of one of them is, for example, Qmax @ Th of 13.0W @ 27 degrees celsius, while the maximal current and voltage are 5.6A and 3.6V.

Are these specs saying something different? Because how can a TEC running at 20.16 watts pump heat at 13 watts, which would mean an efficiency of ~64.5% (even if only at the specific most efficient temperature), when I read their efficiencies are perhaps 8%?