If you don't live with municipal running water stay clear of the tankless water heaters. I live in rural area have water softening unit, water neutralizer & blending tank of 100 gallons but I didn't have 300 gallon holding tank that the rinnai system could draw pre-treated water from so it could supply my 87 gallon jacuzzi or a Shower with seperate wall jets. These Tankless water systems draw water & Nat gas/Propane at an incredible rate in order to utilize quick heat. The plumber told me a designed system in a rural area with water softener/neutralizer, blending tank & holding tank was 10K. installed. Consequently I dropped that Idea & went with a Solar-electric system & (2) 80 gallon tanks one to pre heat the water the other to hold the water & using my existing softener system cost 6k. Plus I do not have to be worried as much at the cost of OIL/Utility bills I think you can presume that OIL (Propane) prices will be high for the rest of our lifetimes. That is the fuel the tankless heater was to use (BTW the cost of the Propane tank was another 5K to have it buried, 2500K if I didn't have it buried on top of the 6K price I just quoted you!

Installing both tank type & tankless water heaters in the attic has been a common practice if Florida, Calif, and other regions in the sun belt for years. In fact, both the IRC & UPC address specific additional requirements for installing the water heater in the attic. 1. The water heater must be located within 20ft of the attic hatchway. 2.There must be at least a 24" wide solid floor catwalk from the hatchway to the water heater location. 3. There must be a 30" workspace in front of the water heater. 4.At the water heater location there must be a 24" solid floor walkway all around the heater. 5.There must be a 120v electrical outlet in the near proximity of the water heater to permit operating power tools when servicing the unit. 6.There must be an electric light in the near proximity of the heater and the light must be controlled by a switch that is placed near the attic hatchway. 7.There must be an approved drip pan with a minimum 3/4"dia drain line that is run outside and terminated by code specification or it must terminate in an approved indirect waste. 8.The TPRV must have a full bore discharge line that goes outside and discharges in an obvious location per code spec or it must discharge into an approved waste receptor at and obvious location. TPRV MAY NOT discharge into the pan. 9. The water heater must remain accessible for service or inspection, (must not be blocked by personal items stored in the attic.) Under the IRC the attic hatch must be a minimum of 22"x30" Under the UPC the attic hatch must be a minimum of 30" x 30" Note, those dimensions are the minimum, but code also says the water heater MUST fit through the opening. That would generally not be an issue with a tankless but with a tanktype you need to check the tank size.

New twist...the old tank is leaking. Just filed a claim under the Home Warranty, so hopefully I can have them pay $ towards what we end up wanting. Fun stuff..

Tankless heaters have used as a marketing idea that they will increase efficiency by not having hot water sitting around in a tank all day not being used. It's an easy concept for consumers to grasp, but it's not true. On an electric heater, the difference in the energy factor is very small between a tank and a tankless heater. A tank heater will be in the area of 0.93 and a tankless might be 0.95 - not enough difference to talk about and certainly not enough to provide payback. That represents the amount of heat lost through the walls of a well insulated tank. With gas heaters it's different. The vast majority of the efficiency gain is in the lowered flue temps. Second is not having the heat loss through the center of the tank. For your situation, what you should know is that a properly installed and operating electric tank heater is extremely reliable and efficient. Get yours replaced or repaired and the TPV properly routed to the drain so that it doesn't cause damage. Since you have lost confidence in your heater, I would just replace it rather than repair. Make sure that you are addressing thermal expansion issues that might have caused the TPV to open. If you want more space, consider a stacking washer and dryer and eliminating the sink. The front loading LG's are full size (huge inside) stack and don't use much water - eliminating the overflowing washtub issue. That would be a cheaper way to get space than a tankless heater and they are great machines.