Why a discrepancy between 2 different branded 300w heaters

[windemerejack]

My heater has just packed up after 8 years so cannot complain, so looking at Schego and Aqua Medic 300w heaters, Schego advertise 300w heater for up to 300 litre tank yet Aqua Medic advertise their 300w heater for 500-1000 litre tanks.
Which is correct and why such a large discrepancy between them? I presumed 300w is 300w no matter what brand.

 

[Ron Reefman]

Yes, but.

How big is the heating element? How far is the element from the edge of the heater? Just because they both use 300 watts doesn't mean they work equally. A 6 passenger car gets 20mpg and a different 2 passenger sports car gets 20 mpg. They both use the same amount of energy, but they don't accomplish the same job.

 

[Crustaceon]

I’d imagine it’s about duty cycle and btu output. Same wattage, better performance.