Even simpler. Take the boost out of the circuit and run with DC right from the panels. You should only be making water when the sun is shining and there is an excess of power.
This is obviously simplest. You won't get MPPT but the simplicity makes up for it.
But I kinda assumed the need for heating is decoupled from the sun shining and there is some significant battery storage involved. If not, I'm all for the simplest possible solution.
PV voltage being too low for existing heating elements could be a problem though.
More information is needed, i.e., a full schematic of all components in question, including the panel string voltage and battery capacity and voltage, if any.
Maybe I'm misunderstanding your circuit, but I have seen some similar claims before so I'll comment about it even if it doesn't apply to your circuit. "PWM from capacitors to get power point and not have conversion losses" doesn't make any sense. You are likely having significant losses in capacitor ESR although it might kind-of work with parasitic inductance. You really need an inductor in the system for voltage conversion (and voltage conversion is needed to track MPPT while supplying loads). Buck, boost or any other power conversion topology works, and you can't completely get rid of conversion loss but properly designed converter can easily run at 98% efficiency. A ghetto converter which lacks important components like the inductor likely isn't as efficient even if the first instinct is that removing the inductor removes inductor loss.