The listing claims that this has the 500 watt heater. Not so. The upgrades to this unit only include a better lid handle, a degas setting, and a half-wave power setting. The 22l model has the 500w heater. This unit has 8 transducers, not 7 as some reviews state. The 20l tank holds ~ 4 gallons to the fill line. The unit works well but it too soon to rate its longevity.