When I first heard of Tankless water heaters, I gleefully imagined we’d be getting a small Hot Water Heater under each sink, or for each bath tub. That would be NEAT. We would be saving water, and saving electricity. In addition, there would be only a COLD water line to each room of need, cutting long plumbing runs in half.
Unfortunately, they didn’t turn out so gleeful.
Tankless water heaters draw up to 100 amps to instantaneously heat water on demand. At that much current you would need HUGE wires to run to each appliance, or at best, one to each bathroom or kitchen. Another problem with the milti room scenario is ‘what if’ the two bath and one kitchen units turn on at the same time? Demand of 300 amps on your load center…
Another problem, I don’t know any electricians who want to wrestle those ‘sausage’ 150 Amp power cables through floors and walls (50% overkill for safety) to your remote upstairs bathroom.
So we end up putting one ‘Tankless’ water heater in the basement, next to the load center. As I stated before, this can be the worst place since you may need to run the faucet a long time in some places before you can rinse the soap off the dishes.
Read the fine print on the Tankless Water Heater brochure. Hot water is not INSTANT. It can take 6-10 seconds to get hot water out the side of it. Add this to the length of pipe going to your faucet. If hot water took 20 seconds with a tank heater, it’ll take 30 seconds on tankless.
So they will waste water.
Modern ‘Tank’ heaters have reached the pinnacle of efficiency Glass/foam lined tanks keep the heat in very well. Cycle time for no water flow is only 30 minutes at 15 amps per day (I ran the test myself - .9KW/Hr). They have grossly exaggerated the ‘cost savings’, saying they will pay for themselves in 20 years.
Tankless water heaters are more subject to corrosion than tanked types. In the WORST hard water conditions, tanks will last 3 years, tankless gum up in 6 months. They are more fragile.
And last of all, there is the SURVIVAL scenario. You lose power, water, cable, roads, and phone from some freak hurricane or snow storm. Tanked water heaters will give you a SURVIVAL supply of fresh water to drink and flush the toilet.