and therefore throws away all power which the Solar Panel(s) are generating above the desired 'battery charging voltage.
If your solar panels are 18.5 volts during peak production times, but your controller wants to deliver only 14.2 volts into your batteries, then your wasted power (power left in the panels by actually disconnecting them, thousands of times per second) ... is about 30%.
PWM controllers are simple, much cheaper and small enough to fit into the panel under the sink. But, if you can find a place to mount a bigger panel, an MPPT panel would only lose about 5% of panel power - converting the other Solar power into MORE useful current at 14.2 volts.
See full explanations PWM and MPPT solar controllers in this Thread, posts #1 and #2:
https://www.trailmanorowners.com/for...71&postcount=1