Tankless Electric Water Heater
Typically come in the 3kW variety, but more advanced ones are 1.8kW. Otherwise, 1.5kW are mini-tank, not true tankless.
- 1.8kW electric on-demand water heater - $159 - comes with aerator, 0.21 gpm activated, limited to 0.32 gpm. . 39F temp rise at 0.32 gpm. 
- Cheapo point-of-use on-demand electric - 3kW - $68 
- 3kW on Ebay, $60 - 
- 2.6kW - 60F rise at 1GPM - on the shower itself - 
About 1.5 kW - worst of 2 worlds - don't have enough continuous hot water, and waste energy. You can tell by their larger size than true tankless.
- Great point from review from a wise electrician - 'I just wanted to clarify a few points in respect to wattage and breaker size...
The element is rated at 1440 watts (at 120 volt), As stated this would be considered a continuous load per NEC 424.3. So, 1440 watts x 125% = 1800 watts 1800w/120v = 15 amp So it seems like 15 amp would be correct? NOT SO FAST. Since the element is a resistive load the wattage rating of the element increases as the voltage increases. Any source voltage greater than 120 volt will therefore put the load on the circuit above the 15 amp rating. Depending on your geographic location there is a very good chance the power company is supplying >120 volts. This may not jive with what you have heard, but after having this discussion with many journeyman electricians over the past 40+ years I've made a point to teach my apprentices the math behind it. see less By LifeTastesGood on September 20, 2019' - ref