Ok, that's really funny. I was reluctant to post this (what am I doing posting this here?) but I thought I remember'd NA had one installed and I was hoping to hear how it went.

Stop reading my brain! I've been meaning to ask folks about these since I have to replace ours soon before it fails at some inopportune time.

Posting a new thread is a tankless job...

Uh oh. Should I be doing this?

If I understand correctly: Hard water builds up mineral deposits in your water heater. Meaning, rocks. The rocks can break off inside and bang around when the water pours in. Ours was doing just that recently but the apt. guys replaced the heater for us. Too bad they're too cheap to get us a cool (hot?) tankless one.

Apartment repair guy is a tankless job.

Anyway, I'm not sure how much the build-up can affect the efficiency of the heater.

It can make a difference, the build-up is essentially an insulator between the heating element (gas or electric) and the water. The more build-up, the more energy it will take to heat the water, that extra energy is wasted.

I have had natural gass tankless (same brand as NA) for around 3 or 4 years
No problems haven't had to replace the burner and has paid for itself but it did replace both a 75Gallon Natural gass and an 45Gallon electric.

it would probably save even more if the roomate would listen and leave the kitchen sink on cold unless he needs hot water.

EM or NA didn't we talk about em before you got yours I seem to recall anyhow glad you like it. Love mine too.