In early 2014 our 55-gallon water heater started leaking... thankfully quite slowly. 

We decided to replace our traditional water heater with a tankless water heater.

Traditional water heaters continuously heat ~ 55 gallons of water, which flows to your faucets when you turn on the warm/hot water.

Tankless water heaters have coils that warm the water as it flows to the faucet.

We ordered our Made-in-USA tankless water heater from TankTheTank.com.  They build their heaters in Hialeah, FL - Miami, FL (in Dade County, Florida).

They have several whole-house tankless water heaters.

We ordered and installed a model N-120 on Memorial Day.  It worked great, providing hot water through the house.

Then, in November, we learned that

1. -the water in our rivers becomes cold
   (ok, we knew that)
   

2. -the water remains cold all the way to our houses
   (we just hadn’t thought about that)
   

3. -the tankless water heater we bought was never meant for such cold water, so while it could heat the cols water, it couldn’t heat it enough, quickly enough, to fill a bath tub (showers were ok)
   

4. -lowering the water flow into the N-120 did let it warm up enough for showers, but baths were paused for a couple weeks
   

5. -a quick call to TankTheTank.com can provide great insights... had we called first, we would have just installed the meant-for-cold climate AH-27 model.
   

So we now have a three-element AH-27 tankless water heater, with hot water at full water pressure through the house!

Cost savings...
We have already seen incredibly low natural gas bills - in the summer only the clothes dryer used gas, which was ok.  We do expect that the electrical bill will increase, and it has, but not enough to offset the reduction in the gas bill.  We will share as we confirm, over time, how good the savings prove to be.

the interim / temporary N-120 tankless water heater:

the original water heater: