The __init__ methods of the various model classes show quite a bit of dublication once the econ_type parameter is integrated. In my opinion, the parameter could be included in the params dictionary. This would already make a lot of things much easier.

On top of that, there are parts of the code (e.g. setup of the self.nw attribute), that is shared for every model and is not affected by any specification. These parts should be included in the HeatPumpBase.__init__ method. Parts, that are individual to other classes should be added in their __init__ method, but only after calling the super().__init__ method. For this purpose it may also be useful. to create an "in-between" level of abstraction, e.g. a TwoWorkingFluidsHeatPump. which has a different __init__ compared to the SingleWorkingFluidHeatPump. These classes do not have any purpose other than the in-between level of abstraction.