Shallow fill waterbeds and normal fill single softside waterbeds require a smaller heater output than other types.  With a lower output heater we can not only save on energy consumption, but increase the mattress's lifespan since it is exposed to a lower temperature.  With time excessive heat will decrease the mattress's lifespan.  The 125 watt output of the Thermal Guardian low-watt heater satisfies the heating requirements of these waterbeds without subjecting them to unwarranted heat.  Similar to its high-watt cousin its controller has a separate receptacle for the heating pad, thereby making heater replacement easier in many instances.