Replacing old solar installation questions

[fresnoboy]

Hi everyone. We recently built a new house, are prepping our old house for renting it out. It was built in 1996, and had 36 Kyocera 167W panels installed back in the 2004-2005 timeframe. A few years ago the Fronius IG5100 inverter failed. It turns out I couldn't replace it because the wiring spec has changed, and the newer inverters are not compatible with the way the original panels were wired. I do have conduit from the attic below the roof all the way to the garage where the inverter is.

I'd like to get solar fixed now before it's rented. Replacing the wiring to put in a new string inverter means removing the panels. Given their age and 167W max rating, I might as well replace the panels as well. I would really like to reuse the racking if possible, because removing it and installing a new set of racks means a lot more hole punctures and possibility of leaks. I've been told that the code also has changed regarding how close the panels can be mounted to the edge of the roof. But even if not all the locations can be used, the newer panels are much more efficient.

Has the racking changed enough since 2004 that I have to replace that too? I did call tesla to see about them doing an install, but they won't remove the old panels and can't use the old mounting because of the system they use. And if I am going to remove panels and the racking, I'd really like someone who would do both parts.

Also, the roof appears to be in pretty good shape, but it is the original composite shingle roof that went on the house when it was built back in 96. So it's almost 25 years old. Should I go ahead and bit the bullet and replace the roof now since I wouldn't want to have to replace it after new panels go on.

Any advice for me?

Thx!
Mike

[bob-n]

Where I live, composite shinge roofs are good for 20 years or so. I can't tell about your roof, but now you know that removing panels is not cheap. So if the roof will need replacing in the next 5 years, definitely do it first. That will mean removing the racks and the rack mounts, so you're back to ground zero.

You didn't mention the rack brand or details, so it is hard to know exactly what you're up against. Even if you told us the brand and model, we probably wouldn't know for sure, but it is likely that you need to replace roof mounts when you replace the roof. Panels have gotten thinner over the years, so even if you reuse the rack, you will probably need new clamps sized to the panels, too. Then it comes to details. Is that rack maker still in business and still selling clamps and mounts for your old racks?

Most of us would advise against any sort of hybrid of old and new, or mixing brands, because it wouldn't be a fully engineered solution and may have risks. It may also void any liability or warranty coverage.

Panel X and Y is relatively standard for 60-cell panels, slightly under 1 meter by 2 meter. Today, you can also buy 72-cell and 96 -cell panels. If you went with 72 or 96-cell panels, you would change the roof design. So best to stay with standard 60-cell panels.

If you use higher power panels and the same number of panels, the power company is going to want to be involved. You'll be pushing more energy onto the grid at noon, and they want to plan for it.

You need to check with your local building inspector to know if you will need to:
1) Get a building permit
2) Get engineering drawings
3) Get inspections
4) Upgrade to modern roof setback requirements (do they grandfather old installations?)
5) Upgrade the electricals (do they grandfather old installations?)

In summary, it sounds like the costs will be fairly close to a whole new solar installation plus demolition, and you will probably want to replace the roof before investing in it. You can probably apply for a 26% federal tax credit and perhaps also some credits from the state, so it may still make sense to do it now.

I hope that this is helpful. Please keep those questions coming. If possible, add details.

[Mike90250]

> the newer panels are much more efficient.
I seriously doubt that. Panel efficiency has only gone up a couple %. Now it's true that your used panels have lost some eff, and that new ones would be more efficient, but
even the best advertised are
"record-breaking efficiency of up to 22.8 percent"
compared to "average" panels of 16%
There are different mfgs and different types (poly vs mono crystalline) but the differences between the same grade/class of panels, is small, just a couple %, not as huge as the salesman implies (up to 45mpg on the hwy)

https://www.azocleantech.com/article.aspx?ArticleID=603

[J.P.M.]

> the newer panels are much more efficient.
I seriously doubt that. Panel efficiency has only gone up a couple %. Now it's true that your used panels have lost some eff, and that new ones would be more efficient, but
even the best advertised are
"record-breaking efficiency of up to 22.8 percent"
compared to "average" panels of 16%
There are different mfgs and different types (poly vs mono crystalline) but the differences between the same grade/class of panels, is small, just a couple %, not as huge as the salesman implies (up to 45mpg on the hwy)

https://www.azocleantech.com/article.aspx?ArticleID=603

And all that's an area efficiency anyway. STC efficiency only means an array using more "efficient" panels will be physically smaller. That's it - besides probably costing more.

For any reasonable quality panel, when new, 1 STC kW of PV from one mfg. installed in the same location and orientation will produce about as much annual output as 1 STC kW of PV from any other mfg., regardless of STC efficiency. The less "efficient" panels will only take up less real estate and probably cost more.

The replacement/additions may be more productive than what's up there now by virtue of being newer and any still working 24 yr. old panels may be getting a bit long in the tooth. I'd expect they've lost about 12-15 % of their original efficiency.

Even if the racking will work (??), I also kind of doubt you'll have an easy time finding a vendor that'll remove old panels, leave old racking in place and add new panels. Not a blow and go type situation that vendors prefer.

Besides, if some PV of some form or another is planned for the roof, it's probably not a bad idea to replace a 25 yr. old roof, and by the time you replace the roof, I wouldn't be too surprised to find it to be more long term cost effective or at least have a lower probability of future leaks/problems to simply replace the existing array, provided MAYBE that it's possible to reuse (or blank off) any existing roof (or unused) penetrations with the idea of not creating leakers, and then add penetrations for new racking as required. Maybe a bit unusual, but kind of an interesting design situation with no single best approach/solution.