It is a closed loop, they run muni water through the towers in open loop to cool the closed loop. As far as how much cheaper? Well, heat pumps basically double

It is a closed loop, they run muni water through the towers in open loop to cool the closed loop. As far as how much cheaper? Well, heat pumps basically double your power costs, air handlers are highly contingent on reduced density and/or cool environmental air, so, alot cheaper to run the tap, no doubt. It's more an issue of waste. That water, at that scale, should be treated and fed back into the system, but it's just discharged instead.