Originally Posted by Medwed
You only run out of hot water when you have a water tank to draw water from. Tankless water heaters by design cannot run out of hot water, unless of course they are broken and need replacement.
Tankless heaters also heat the house if you have water heating system like I do. No variation in water pressure or water temperature with tankless heaters.
Tankless heaters have to decide how much water to heat, and it takes time for the water to work its way through the maze of pipes inside it. For whatever reason, they tend to put out water with significant variations in temperature when you vary the demand. I'm hardly the only one who's noticed this.
Also, tankless heaters don't run out of water; they run out of the ability to heat the water to your desired temperature when too much water is pulled through. Maybe if you use Government Approved 1.5 gallon-per-minute shower heads and faucets everywhere they can handle it. But where water isn't scarce, that sucks. And try filling a tub with one.
Originally Posted by mike1445
tank style water heaters are $350-1000 with a lifespan of 12 years, tank-less are $800-1400 with a 20 year lifespan and energy cost savings of 30% or about $100/yr for a 2 person home, savings seem substantial enough for me. Price varies with volume for tank-style and output (gpm) for the tank-less. If your friend has 3 it's because he probably bought multiple lower priced units small outputs,
Those numbers are based on very unrealistic assumptions about how much water will be used. Real people use way more water, and the more you use the better the tank style heater does.
But don't take my word for it. Here's the top three hits from google:
Probably not. Gas tankless water heaters, which use high-powered burners to quickly heat water as it runs through a heat exchanger, were 22 percent more energy efficient on average than the gas-fired storage-tank models in our tests. That translates into a savings of around $70 to $80 per year, based on 2008 national energy costs. But because they cost much more than storage water heaters, it can take up to 22 years to break even—longer than the 20-year life of many models. Moreover, our online poll of 1,200 readers revealed wide variations in installation costs, energy savings, and satisfaction.
Tankless units might need more care
During our long-term testing, an indicator on the tankless model warned of scale buildup. We paid $334 for special valves and a plumber to flush out the water heater with vinegar. Many industry pros recommend that tankless models be serviced once a year by a qualified technician. Calcium buildup can decrease efficiency, restrict water flow, and damage tankless models. Experts suggest installing a water softener if your water hardness is above 11 grains per gallon. Ignoring this advice can shorten your warranty.
Since water heating represents about $20 of the average FPL bill, the savings for a tankless water heater would be less than $2 per month for a typical customer.