They provided further details privately. The conclusion was the pricing of the Hoymiles HSRD-2C devices was not materially different than the commonly available and seemingly equivalent Tigo TS4-A-2F devices. I dislike the RSD requirements, so anything I can do to reduce the cost impact of them is worth looking into. The UL 3741 change will basically eliminate them for the most part, but timing is such that code and vendors have not caught up to that yet, sadly.Ncsolarelectric is one of the handful of distributors so you could frame the question as availability from him.
For new installs, it is fair to compare DC versus AC. From my perspective, DC coupled is going to be more efficient since PV to battery has no unnecessary mid path conversion to and from AC produced by micro inverters. So your energy in the battery gets there with much higher efficiency. The battery to load/grid will be the same for both systems, so overall PV to battery to load is better on DC coupled. This is not news.Also AC coupled solutions need to be compared to other AC coupled solutions in efficiency, when used in retrofit.
An AC system with battery means you buy two inverters, the array of micro inverters on the panels, and then another one that is battery to load/grid. The Enphase battery system even uses plugged in micro inverters to make that explicit. A DC coupled system only has one inverter, PV and/or battery to load/grid.
Their micro inverters do seem generously rated. Hopefully this doesn't impact their efficiency at partial loads too much.You previously had a concern about clipping. Hoymiles oversizes their microinverters so they don’t clip (500W per channel). On their 4:1 microinverters they do still cost a healthy chunk above RSD. Personally I think their products are great for odd size roof planes and shading
When I pencil out the systems I am considering, DC coupled string inverters win on cost and efficiency. Long term, a string inverter inside the building seems like it will last longer than the extreme temperature cycling of the micro inverters on the roof. The go from the cold of night to the baking heat of full sun under a hot solar panel and that temperature cycling wears out electronics.
Mike C.
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