The TCH in ECO mode will let the AC run full power (or near it) as long as the interior temp is 75 or greater. Then it throttles down to save energy. The result is that in demanding conditions (hot and sunny) you can't get the temperature to drop below 75 in ECO mode. You don't broil, but you don't freeze either.

Setting the temp control at its extremes or turning on the defroster automatically cancels ECO mode. In a IMHO design flaw, the ECO button has no memory, so turning off the defroster or resetting the temperature leaves ECO off. The ECO button seems to be an afterthought as it is located virtually under the dashboard to the left of the steering wheel instead of being in the climate control cluster. Very inconvenient.