*Cost* implements the cost function. One of it’s properties
is price of the electricity (kW−h). We suppose that all electric energy is transformed to heat energy.
Also, usually we have price for (kW−h), but in our model we have (J), so we transform between them using
1kW−h= 3.6e6J.

The output value of *Cost* component is accumulated cost of the house heat-
ing/cooling. The input is the heat flow from heater/cooler.