Central inverter and String inverter Comparison

Central inverters are either of limited size themselves (ie. 100kW each) or internally made of independent units (ie. 50kW for Gozuk inverters, others have similar setups). This already gives one many MPP trackers for a multi-MW solar field, so partial shading of the field due to clouds passing over should not have much if any effect in comparison to string inverters. Sure, string inverters give you a lesser loss in case one fails. They also give you many more points of failure, so you'll be replacing more of them and more often. Both string and central inverters should work OK now with thin-film panels; that was a firmware issue with how MPP tracking is done and I can't imagine any manufacturer that has not addressed that by now. Both with string or central inverters one should have a diligent program in place to make sure there is no partial shading of panels (ie. leafs and such); it affects both badly (though in a different way than the writer above alludes to). The latter may be a bit easier to catch with central inverters as they are usually installed with managed/monitored string combiners.

In terms of money, string inverters will get more and more expensive vs central inverters as the field size increases. It's a heck of a lot of additional labor to hook up 100 string inverters of 10kW vs. 3 or 4 central inverters (which can also be bought in pre-configured 1MW units with some of the connections already done).

Personally, I would draw the line around 250 - 400 kW. Below that string inverters work out well. Above that central inverters have their place (and will save money). Can it be made to work either way, and work well? Sure!