Seisco Tankless Water Heaters Review

A review of the whole-house and point-of-use Seisco tankless water heaters for heating potable water in residential applications. Explore the popular models and see what makes them different from other manufacturers.


Seisco tankless water heaters are small and very efficient electric units designed to continuously heat water on demand and deliver it in endless supply.

They are great for replacing traditional tank-type water heaters as a booster for the existing conventional, solar, and geothermal water heating systems.

Popular models

All the models listed below are grouped into two categories: two- and four-chamber, and can provide enough power not only for point-of-use service but whole-house water heating:

  • RA - 9
  • RA - 11
  • RA-14
  • RA-16
  • RA-18
  • RA-22
  • RA-24
  • RA-28
  • RA-32


Seisco RA-14 is the two-chamber water heater used for single applications, such as one kitchen or bath sink or shower, or as the supplement of the existing conventional tank-type water heater. There are two types of RA-14, one that requires 208 V and the other 240 V service. RA-14 is recommended for areas where the incoming water temperature is above 75 F.


Seisco RA-16 is the largest 2-chamber model designed mainly for use in small apartments and condos and where the incoming water temperature is above 70 F. As the model RA-14 also works great when combined with the tank-type water heater or in recirculating systems.


Seisco RA-18 water heater is the smallest 4-chamber tankless and electric water heater recommended for use in smaller homes, apartments, condos, and cottages located in the warmer regions, where the temperature of the incoming groundwater is above 65 F. It is used as the whole-house unit, solo or combined with the tank type that cannot satisfy the demand for hot water.


RA-24 is used in homes and light-duty commercial applications to easily replace a tank-type water heater with capacities from 30 to 50 gallons and the 208 V service.


RA-28 is the most popular residential tankless and electric water heater from Seisco. It is recommended as an ideal replacement of tank-type water heaters with a capacity from 50 to 80 gallons. It is built for use in homes where the 208 V or 240 V service is required.


Seisco RA-32 is the largest whole-house water heater, designed for high-demanding residential and light commercial applications. It works great in combination with the tank-type heaters to supply hot tubs and spas.


Seisco tankless water heaters for point-of-use service are a great solution for heating and delivering water fast, where it is needed. These are mainly used as the under-sink units, providing hot water to one sink and where the main whole-house water heater is distant.

2-chamber models

Model RA - 9 RA - 11 RA - 14
kW 8 10 14
# elements x watts 2x4000 2x5000 2x6000
Btu/hr 27300 34130 40950
Temp. rise @ 2.5 g/min 20 25 32
Voltage (V) 208 208 208 (240)
Amps (A) 38.5 48 58
Circuit 40AX1 50AX1 30AX2

4-chamber models

Model RA - 18 RA - 22 RA - 24 RA - 28 RA-32
kW 18 22 24 28 32
# elements x watts 4x4500 4x5500 4X6000 4x7000 4X8000
Btu/hr 61430 75080 81910 95560 109211
Temp. rise @ 4.0 g/min 30 37 30 48 55
Voltage (V) 240 240 208 (208) 240 240
Amps (A) 75 91 115 116 133
Circuit 40AX2 50AX2 30AX4 30AX4 40AX4

Top features

One of the top features found in Seisco tankless water heaters is the patented power-sharing distribution system that simultaneously provides an equal amount of heat when water passes through the heating elements, therefore, preventing the high temperatures, scalding water, and excessive mineral deposits. This way, the unit operates longer, and the users are less prone to scalding burns.

Every Seisco product comes with full-power control, so there is no disturbance in the current flow. In the low demanding periods for hot water, the microprocessor reduces the power level to the minimum, so there is no waste of energy. The power level depends on the flow rate and temperature rise, and the water heater uses only as it is needed to heat the water.

Safety features include dual low-level detectors that prevent dry firing of the heating elements and a leak detector that sounds an alarm if there is water leak. For easier troubleshooting and maintenance, the water heater incorporates the microprocessor with the diagnostic software.

All Seisco tankless water heaters are built in two sizes, and most of their parts are identical, which almost guarantees the availability of the parts. They are strong, high-performing water heaters that are made of materials that are rust and corrosion-resistant.