I'm not sure why we would want to replace mechanical systems. A portable AC unit with 10,000 BTUs uses ~650wh these days, and it'll turn a 50m^2 apartment into an icebox. That's not much more than a flagship GPU pulls. This is also about the least efficient class of aircon you can get.

Sure less energy usage is always better, and if we could get the same out of mere single digit wh power draws that would be cool. But I don't think thermoelectrics are ever going to get us there.