Run tap water through the IC for 5 minutes. Even with the tap at 85F, the wort will hit about 110F. From there, switch to a pond pump in a bucket of ice water.
This is the most efficient way. If you try to use icewater only, it's going to take more than a bag. In any case, nothing is free. If you need 3 bags of ice, that's $5+ and a lot more than it would cost for the 30 gallons of water you usually burn in an IC chill. If you argue that you can make your own ice, true but that's a lot of electricity to do so. We usually write that off in our mind because we have a freezer running anyway, but how many people know that putting anything warm in there immediatey starts the $$$$ compressor?