Read some independant reviews of MPPT controllers.
My opinion is generally the MPPT money is better spent on more panels, for more power all the time instead of just sometimes.
They could be OK if the system is quite large. I never put a system in large enough to have a MPPT that would gain nearly as much as the same money spent on more panels.
A quote from windsun.com. And they are trying to sell them!
""Some MPPT's on the market don't give you as much you would hope for. The reason is efficiency. So you gain 25% by adding a MPPT - that does not help you much if your MPPT is 85% efficient. You've only gained about 5 watts - not much to get excited about..."" ""$500 to $1200...""
$500 to $1200 gets a lot more than 5 watts of panel!
The extra PVs will last what, 50 years? Who knows. But I can't see a high percentage of fancy controllers going even close to that long.
G-