The height and color of the pin indicate an estimated load. The load is computed interactively as a function of temperature and time of day from a simple model. The temperature dependence is based upon a polynomial approximation of the relationship between historical data of power demand and weather observations. The temporal variation is based upon a spline fit of hourly electricity requirements for mid-week days in an urban tropical environment, which is consistent with other results in the literature. The function is scaled by the rated power plant capacity using published data.
Heat index is used as a more accurate measure of demand than simply temperature.
The weather model results are interpolated at each time step to the location of each of the power plants.