Be careful about wattage specs, many units will say "200 watts" (or whatever) but what it really means is a "total" of 200w for both the transducer and the heater. Look for the "transducer" spec! There will be a spec for the Frequency (usually 42khz), the wattage of the ultrasonic transducers, and the wattage of the heater. The one you are most concerned with is the transducer wattage. For example my latest unit is a 3 liter 220w model with a 99 minuter timer. It has two 60w transducers and a 100w heater. I have seen 250w models which at first glance sound more powerful but that were really a single 50w transducer and 200w heater. This would be much less effective for our intended use. In our application we care about the transducer wattage much more than the heat. I find that if I start with hot water I dont need any heat at all as the operation of the unit generates plenty enough heat all on its own.
shop for the most transducer power you can afford, even if it doesnt have any heat. The small cheap ones usually have a 35w or less transducer, and are also less efficient in design, ie the use of plastic etc, but they will work, it just takes longer than a fancier model.
