At a cost of $0.134 per kWh, this amounts to $120.60 per month. A large 12,000 BTU air conditioner, like that in a window, running six hours each day will consume 270 kWh, at a cost of $36.26 per month. A smaller 6,500 BTU room air conditioner will consume 144 kWh at a cost of $19.34 per month.