Well said! Good luck!You are correct I neglected the gas costs as I do not have any data at this point for the gas. I did mention that in the sentences right after my guestimation of monthly savings.
As @Triggreef mentions, I am using the gas water heater so not getting the electrical pull. I agree with you the electric wouldn't make sense because of the inefficiencies and still using electric.
Just looked at my bill. $.13111 per kwh. I don't really have delivery charges. They charge a fee per day, but I am getting charged that no matter what.
You are correct, the water returns to the water heater. So the loop uses no water, just the heat from that water.
You are correct, there is no energy savings. I agree with you that I am actually using more energy to heat my tank because electric heaters transfer basically all the energy into the water. The hot water heater is only so efficient at using gas, holding the heat in the hot water, and the insulation around the piping running through the house also allows heat to leave.
The savings simply comes down to two things.
1. Gas is much cheaper than electricity.
2. The marginal cost of the hot water heater setup is only the difference in what is already being used to maintain hot water for use and what it now takes to maintain that hot water with my system in place. I am repurposing heat that would normally go unused sitting in the water heater.
To your last point, yes a hot water heater is more expensive, but the marginal reduction in the life of the water heater is the cost of using my system. I am not sure what that will be, but I also know that I have replaced a whole lot of electric heaters in the past 5 years. Let's keep my loose math and examples going...
Hypothetical
Hot water heater costs $400 and has a useful life of 12 years. With the added wear and tear from the fish tank heating it now only lasts half as long, 6 years. Cost $200.
Electric Heaters
Cost $30 plus dollars each. 1 per year replaced(I've replaced way more than that, but they get used for various things from QT's to mixing containers, etc.). Cost $180+
Not a whole lot of cost difference there. This is all before we add in the many other benefits I alluded to previously. Electric heaters fail frequently, shock you and inhabitants, break, etc. Hot water heaters still work with the power out and running a pump on a generator in extended power outages is much easier than running a lot of power to keep the system heated. It heats water much faster. Etc. Etc.
Are these setups for everyone, definitely not. A number of variables go into whether setting one up would be worth it, however, in my case I know I will save money, just not to what extent. I look forward to seeing how it plays out and how much I save.