At roughly $330, ET180 is attractive for one or two modest simultaneous fixtures in the right climate. It is not a universal whole-house answer.
Core specifications
ThermoMate lists the ET180 at 18 kW, 240 V and up to 4.58 GPM. The unit allows digital temperature adjustment from 80°F to 140°F.
Electrical requirements are substantial: the current product page specifies up to 76 amps, two double-pole 40-amp breakers and two 8-AWG conductors.
What “up to 4.58 GPM” means
That number is not available at every inlet temperature. A tankless heater produces less flow as the required temperature rise increases.
For a cold-climate winter inlet, sizing should be based on the manufacturer chart rather than the headline maximum.
Hard water and maintenance
Any water heater can accumulate scale when hardness is high. ThermoMate separates heating elements from water tubes to reduce direct scale exposure, but that does not eliminate mineral deposition throughout the system.
Homes with very hard water should consider treatment and a descaling schedule.
Best buyer
The ET180 is best for a household with confirmed electrical capacity, moderate flow requirements and a climate where the inlet temperature does not demand an extreme rise.
Large homes with simultaneous showers may need a higher-kW model or a gas solution.