The PWM controller is in essence a switch that connects a solar array to the battery. The result is that
the voltage of the array will be pulled down to near that of the battery.
The MPPT controller is more sophisticated (and more expensive): it will adjust its input voltage to
harvest the maximum power from the solar array and then transform this power to supply the
varying voltage requirement of the battery plus load. Thus, it essentially decouples the array and
battery voltages so that there can be, for example, a 12 volt battery on one side of the MPPT charge
controller and panels wired in series to produce 36 volts on the other.
It is generally accepted that MPPT will outperform PWM in a cold to temperate climate, while both
controllers will show approximately the same performance in a subtropical to tropical climate.
In this paper the effect of temperature is analyzed in detail, and a quantitative performance comparison of both controller topologies is given.