dogfish, most of the spec sheets I've seen on tankless heaters so far have stated they draw 100+ amps depending on size. Some I've seen with an amperage rating of 150 amps for the 7gpm ones. am I reading the spec sheet wrong and that amperage rating is actually amperage spike and not running amperage? You say yours is only on a 20 amp circuit? Which model do you have? My house is 1/3 the size of yours. 800 sqft. No joke. Haha.