The rate the electric compressor draws energy from the battery makes a difference in things like how soon/how often/how long you can go into EV mode and how much the ICE runs in general to keep the charge up. There is a thread on another forum where Dan (who visits here from time to time) gave more details. IIRC - it is anywhere from 1-2 MPG cost to run in full mode as opposed to ECO - again this would depend on your local ambient temperatures and sun conditions.

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