camelot-forum.co.uk

Well, maybe they are not worth the extra money.
Gary articulately explains to us why not.

What it does not explain very well is you need a good Max Power Point Tracker (MPPT) in the inverter for the bypass diodes to work. Some cheaper inverters will only work with a small amount of shading, say one or two segments of a panel. But get a decent inverter with a global MPPT function like an SMA inverter and set the shade management function, it scans a large range of voltages every few minutes. In this case optimisers are hardly worth it apart from the individual panel monitoring function.

Where optimisers really come in is fitting together complicated strings with different panels, panels pointing different directions and panels with differing slope angles.

Or on the cheaper inverters where the MPPT does not do global peak max power point tracking with more extensive shading.

Andreas Speiss in Switzerland did some tests on this recently, too, in this video, and came to much the same conclusions about optimisers: