My installer has not decided yet which inverter to use for a grid-tie-only solar PV installation, a Fronius IG Plus 7.5 ( http://www.fronius.com/cps/rde/xchg/SID-DEFE32D8-A55877F7/fronius_usa/hs.xsl/2714_1481.htm ) or a SMA Sunny Boy 7000US ( http://www.sma-america.com/en_US/products/grid-tied-inverters/sunny-boy/sunny-boy-5000us-6000us-7000us-8000us.html ).

Both have approximately the same max recommended PV input power (about 8.7 kW), both use a fan for cooling, and both offer a 10 year warranty.

One significant difference is the Sunny Boy weighs 141 lbs versus the Fronius at 57 - don't know why.

My question is, does anyone have an opinion on why one versus the other inverter would be better for a rooftop system (36 panels @ 225 w ea) where the inverter is mounted inside a garage?

Many thanks!

Best regards,

Bill

Bill I don't know if you made a choice yet and I don't have an answer for you but if you ask over on Wind & Sun they will tell you more than you want to know about the two. My guess is you already looked in to logging on them and I am sure someone on Wind & Sun can tell you which is better for that as well.

I think one unit might be fan cooled and one is passive cooled, but I wouldn't swear to that. All my stuff is battery based.

Brock, thanks for the note.

The decision was made by my installer, and was based on availability.  At this particular moment, the installer was unable to obtain a Fronius IG Plus 7000, and thus proceeded with the Sunny Boy 7000.

It's twice as heavy as the Fronius, and thus my guess is the Sunny Boy is a more traditional design with a big heavy transformer (and perhaps the Fronius is even tranformerless - i.e., some kind of high frequency switching design).

Both units use fans for cooling.  My Sunny Boy has two that will need to be kept clean.

Thanks for the reference to the Wind & Sun forum.  I had been using the Solar Power Forum.

Best regards,

Bill