Its amazing when dripping a small amount of water how much it can change your temperature. My hotwater heater is gas powered and at least for now gas is a good bit cheaper then electricity. After months of looking at everything and checking the bills and useing a meter to check the power that was used for my tank running the drip system and using the hot water to heat it came out to a little less or the same price as just running the heaters on my tank, I would still need to do water changes on top of that if I was running the heaters in my system. Of course all water is different, all tank sizes would be different so what works for me might not work for you. My friend is going to try it with him 300ish gallon tank and see how it goes for him.