Yes, I think this is true. Vaillant certainly underrate their units while other manufacturers overrate their units. There should really be a standard for nominal output. It’s even more confusing sice some heatpumps share components e.g a 3.5kW Vaillant uses the same compressor as a 5kW unit, while a 8kW Samsung HTQ uses the same compressor as a 14kW unit therefore the capacity of these units are much higher but the high-end modulation suffers.
