New system in parallel with 2011 vintage Sunpower system.

[Stomp]

Curious whether anybody has done this. I have a Sunpower 5.83kw AC system that I had installed around 2011 and so far it has been working pretty well. The problem is that 1.) we're using the AC a lot more than we used to and 2.) considering getting either an all electric or plug-in hybrid as the next car. The electricity demands of these *might* make a larger system worthwhile (I still need to run the analysis). We're probably starting a remodel next year that could result in the existing system coming down for a period of time, so I want to research my options.

Obviously panel prices have come down a ton in the past 4 years. I assume my options would either be upgrading my inverter and adding more Sunpower panels OR adding a second system that would run in parallel. The benefit of the second system as I see it is that 1.) I'm not beholden to the more expensive Sunpower panels, 2.) I don't need to toss my old inverter, and 3.) the part of the roof that I'd add panels to has partial later-afternoon shading, so running a system w/ micro inverters to get the most bang for the buck from each panel in the array could make sense vs the traditional single inverter.

Economics of adding to my system vs. using grid electricity aside (I can run that analysis later), any knee-jerk reactions from people here on which option would be the better to pursue?

Thanks,

Derek

[inetdog]

Whatever you do to expand, you will technically need to redo your POCO interconnect agreement and get new permits and inspections.
But going beyond that, there is no particular drawback that I can think of to installing separate panel array(s), new GT inverter, etc. in parallel rather than expanding the old system.

[sdold]

I helped a friend do this for the same reasons and it worked fine. The permits and PG&E agreement modification were no problem. This was a microinverter system added to an existing central inverter system. The systems are 100% separate until they enter the main panel, each on their own breaker.

[inetdog]

I helped a friend do this for the same reasons and it worked fine. The permits and PG&E agreement modification were no problem. This was a microinverter system added to an existing central inverter system. The systems are 100% separate until they enter the main panel, each on their own breaker.

The 2014 NEC seems to require that all PV AC outputs be combined and run through a single disconnect or backfed breaker. Who knows what any particular inspector will or will not allow.

[thejq]

To expand and keep the original warranty, you might have to get the original installer involved. Depending the wattage of your current inverter and additional capacity you have in mind, you might not need to change the inverter, but you still need to buy the same type of panels (assuming you can). If either is false, you probably better off with a new system which you have a lot more choices (micro or solaredge with different/cheaper panels), but you might be forced to upgrade your main breaker panel for the added ampage.

You will probably be better off waiting until you get your EV or PHEV, so you know what the consumption will be. Depending on where you're located, there might be EV-TOU plans that you can take advantage of. I know quite a few people (incl. myself) not having to increase the system size, with additional EV usage, simply by shifting usage (AC, charging, laundry etc) to the cheapest period, while maximizing generation in the most expensive period.

[sensij]

OP is in CA, still on 2011 NEC. SCE's TOU-D-A or TOU-D-T plans could be a nice alternative, if you haven't checked them out yet. Putting a system in parallel on its own breaker should have no effect on the warranty of the original system.

[peakbagger]

I have three arrays with inverters of separate vintages. They all terminate in a separate subpanel which then feeds one backfeed breaker on the main panel. It makes sense to keep the new array separate from the Sunpower system to keep the warranty. My utility keeps the same permit number but revises it. None of my systems have warranties on the panels as they are from defunct companies. Since you have decided to go with microinverters on the new array it sure doesn't make sense to retrofit the Sunpower panels with them.