I installed a new 8000 BTU window mount air conditioner on the weekend on a wall that is west facing. I plugged it into a Kill-A-Watt to monitor its power consumption and noticed in the morning, when the house and the outdoor temperature is at its coolest, it consumes 620-640 W. In the afternoon when the sun is on the unit, it consumes ~750W. Since the air conditioner is way undersized for the space it's trying to cool, it runs at max for the whole day (we shut it off at night since it's in our room and it's crazy loud).
In the morning, the indoor temperature is probably ~22ish C and the outdoor temperature is around 20C, and the afternoon the outdoor air temperature is around 29 C.
It didn't sound like the cooling fan had multiple speeds to account for an increased power consumption when the fins are hot. Is there anything else (electrically related) that could be causing the power consumption to increase by about 100 watts in the afternoon?