ThermoMate currently has lower list pricing on comparable electric sizes. Camplux wins on breadth and a longer advertised cookie.
Price and power range
ThermoMate currently lists 18 kW around $330, 24 kW around $360 and 27 kW around $430. Camplux currently lists 18 kW around $420 and 24 kW around $480.
Promotions change, so the more important comparison is the required flow at the local temperature rise.
Electrical requirements
Both brands sell models that can require very large electrical loads. Before buying any 18–36 kW heater, confirm service capacity, breaker positions and conductor sizing with the installation requirements.
Which brand fits which buyer
ThermoMate is attractive for a price-sensitive electric-only buyer. Camplux is more useful for households comparing gas, electric, RV and outdoor hot-water options from one brand.