Brainstorming System Expansion on New (to me) Home

[jimmyz80]

I recently moved into a new home, which included a 7.28kW SolarCity (now Tesla) system. I've not had solar in the past, but understand most of the concepts at a high level. The existing system is 28 x REC260PEZ panels at 260W each, and an ABB PVI-6000 inverter. This system may have come close to meeting the needs of the previous homeowners, but we brought along two electric cars that they didn't have, so I'm exploring ways to add some capacity to the system. The house already has a pool and a spa, so it's relatively energy hungry.

My big dilemma is roof space. The existing system occupies nearly all of the SE and SW facing roof areas, with most of the remaining space facing NE and NW. The roof is a 4/12 pitch, so it seems like the panels facing away from south would get some sunlight in the non-winter months, but in the winter months I suspect they'd be pretty much useless with the sun low in the sky.

From my online exploring, it seems like modern panels like the LG NeON R are significantly more efficient than the REC panels I currently have, with nearly the same footprint. Would it make sense to get a quote from a local installer, to replace all of the panels with something like the LG NeON R, and then swap out the old ABB inverter for something like a SolarEdge SE10000H? Or would it make more sense to just install a second system on the sub-optimal roof faces, and oversize it a bit to get the output power where I want it? If I go the route of re-paneling my existing system, would any of the old equipment have any residual value at all?

Thanks!

[Mike90250]

i'd wait till the panels start to fail before changing things and making leaks in the roof.

[Ampster]

I don't see anything about your usage, anticipated usage or production estimates. That is where I would start with any kind of brainstorming. That is probably implicit in Mike's post above.

[Mike90250]

> From my online exploring, it seems like modern panels like the LG NeON R are significantly
> more efficient than the REC panels I currently have, with nearly the same footprint.

While you may think that, why not give us the numbers you saw and we'll find out for sure. In the last 10 years, panel efficiencies have gone up a little bit, and I suspect it's specmanship and a pile of asterisks ! *

* Your mileage may vary

[bob-n]

Mike's intuition is very good. Without any math, I'd go with his feeling.

Ampster also makes a good point to do the math. It will confirm what Mike says, or, very rarely, surprise us.

I'm a big fan of a web tool PVWatts.nrel.gov Using this tool, you can enter your location, your roof angle, your roof direction, your panels, and other parameters, and it will tell you what you will produce over a year. You can run the calculation for your current array, the same array with newer panels, and a new array on a different roof face. When you hit a question that you don't understand, like system losses, leave it at default for a quick estimate.

Just to give you a gut feel, estimate $3 per watt for installed cost. In other words, to install 5kW worth of panels and inverters, figure roughly $15,000 cost. It may be $10,000 or $20,000, but that will give you a sense before getting quotes.

Then you can compare the expense and production for each alternative.