diy solar

diy solar

Used vs new panels for roof mount

Disturbedfuel15

New Member
Joined
Aug 12, 2023
Messages
73
Location
Mich
Hello!

I get a lot of FOMO and purchase when I see a good deal. So I currently have 40 235w vinyl-cracked solar panels from Santan solar ($1400 shipped to me). I also have about 20 10ft Unistrut/Superstrut struts for mounting the panels to. My original idea was to ground mount, until I was kicked in the mouth with an almost $5k quote to remove a large tree where I wanted the ground mount to go. In lieu of that, I'm chopping down a smaller tree that will give my roof all-day access to sun. I'd like to still use the strut, as I paid full price for those. I used it elsewhere for my battery rack, so it made sense at the time to buy it all in one go (shipping). The idea is to mount the struts to something like Unirac Flashloc or Quickbolt on my roof. End of backstory.

My question centers around using these used panels vs buying some brand new ones. Keep in mind, I didn't get to use the 30% tax credit for the used panels, whereas I'd be able to with regards to brand new panels. I don't mind spending double what I've already spent on new panels if it means I won't need to go on the roof as often. I couldn't imagine it being the middle of winter, needing to replace or bypass a panel on the roof. My roof is only four years-old, so I'm not worried about the integrity of it. I also feel like using less panels of greater wattage and greater efficiency would mean less square-footage of panels equaling the same output. I could get more wattage out of my roof if necessary, adding panels as necessary. I want all the panels to be the same for aesthetics.

If this were ground mount, I wouldn't be asking this question, as maintenance is easier. Climbing on my roof for maintenance, not as easy. Also keep in mind I could get at least half of my money back selling these used ones, I'm sure.

The main reason I'm asking this is to avoid what I'm doing, and have done countless times--buying twice amidst new knowledge. This community is oozing with knowledge, so I'm reaching out. Constructive criticism is always welcome.

Thank you kindly in advance!
 
After the tax credit some of the new ones are not much more expensive and will last longer. Also higher wattage so lower mounting cost. You paid about .14/ watt and new ones after tax credit can be as low as .2/watt
 
$5000 to remove a tree? If you do go to the roof mounting I would endorse the idea of new panels. The concept of using used panels at all these days, with the price of new being what it is, does not make sense for long term usage.
 
If you only have to visit your roof once, that’s a big win. Put up as many panels as you can in one go and bring each string back to the inverters separately in case you need to test or reconfigure without making a roof visit.
 
Well this pretty much validated my thoughts. I'll probably end up going with something like one of these:

Gotta do some research on panels now, bifacial vs non, good brands, things to look out for, etc. I definitely don't want to buy another pallet. My wife may leave me 😅

Thank you all for your opinions.
 
If they are going to go on the roof bifacial is a waste of your money, however there are less tariffs on those, so they may end up being very close to the same price as regular panels.
Next train of thought has to be what inverter fits your needs....what are your needs and desires ?
Maybe an Emporia energy monitor is your next purchase, to see where your energy is actually going and how much per minute/day/month.
 
If they are going to go on the roof bifacial is a waste of your money, however there are less tariffs on those, so they may end up being very close to the same price as regular panels.
Next train of thought has to be what inverter fits your needs....what are your needs and desires ?
Maybe an Emporia energy monitor is your next purchase, to see where your energy is actually going and how much per minute/day/month.
Thank you for the knowledge.
I already do have two SMA SI-6048s, 70kw ESS and two Sunny Boy sb5.0-1sp-us-40 string inverters. I haven't updated my build thread, but I should. I've got a ton of pictures, it would just take awhile.
 
Thank you for the knowledge.
I already do have two SMA SI-6048s, 70kw ESS and two Sunny Boy sb5.0-1sp-us-40 string inverters. I haven't updated my build thread, but I should. I've got a ton of pictures, it would just take awhile.

I of course approve of your excellent taste in inverters.
What does the 70kw(h) consist of?

Are you doing grid-tie net metering, or offgrid?
I don't think the Sunny Boy -40 inverters have the latest required grid-interactive functions that the (now discontinued) -41 models do.

If on-grid, 2x SB5.0 is about 80% of the limit that can pass through SI relays. If off-grid, SI could handle maybe five of those SB.
But you're probably limited by roof area, as I am on my coming build.
 
I of course approve of your excellent taste in inverters.
What does the 70kw(h) consist of?

Are you doing grid-tie net metering, or offgrid?
I don't think the Sunny Boy -40 inverters have the latest required grid-interactive functions that the (now discontinued) -41 models do.

If on-grid, 2x SB5.0 is about 80% of the limit that can pass through SI relays. If off-grid, SI could handle maybe five of those SB.
But you're probably limited by roof area, as I am on my coming build.
I'm one of the ones who bought the batteryhookup CATL modules. I'll update my build thread soon. This is it. https://diysolarforum.com/threads/first-system-build-thread-another-71kwh-diy.69341/
I've got the JK inverter BMS talking with the 6048s. Data manager M is sending all the data I could need to Ennex OS sunny portal. I'm really happy with it all.
Right now just acting as house battery backup. Did you know SI 6048s are primarily battery backup inverters? Saw it on a training seminar.

I'd like to eventually be off grid, but in reality, I'm not sure if I have enough property here where I live for all the panels it would require. I have no interest in selling back to the grid. I have the SI set to export absolutely nothing to the grid. I'm only using the grid for charging.

By the way, the $5k removal is the only quote I got, and they are a company from an expensive city nearby. I had no idea, everyone suggested them and I didn't look at where they were from at first. If I got it down, I could fit a respectable array where it was. It's also half dead, so I don't feel that bad about it. Who knows, I'll get more quotes but the smaller one blocking my roof I can take down myself. I'm going to to put panels on my roof no matter what. We will see what happens in the future with regard to other quotes.

Thanks for your replies, and also, if anybody wants to take a crack at cutting down the tree, happy to provide more info. Happy to give you all the tree you can take and $.
 
I think Sunny Island is primarily an off-grid inverter for AC coupling and use with a generator. But also has UL-1741 anti-islanding and backfeeding the grid, with a kludge of DC coupled PV pushing battery voltage higher than it wants.

At this point, SMA might sell them as backup to US on-grid customers. And that is how I'm using them, with export allowed from my Sunny Boys.

How do you avoid export? Have SI disconnect when Sunny Boy production exceeds loads + charging? Or Sunny Boys operating zero export (which I would expect to have an issue deciding what is exactly zero, a problem when grid disconnected.)

Or PV & SB not yet installed?
 
I think Sunny Island is primarily an off-grid inverter for AC coupling and use with a generator. But also has UL-1741 anti-islanding and backfeeding the grid, with a kludge of DC coupled PV pushing battery voltage higher than it wants.

At this point, SMA might sell them as backup to US on-grid customers. And that is how I'm using them, with export allowed from my Sunny Boys.

How do you avoid export? Have SI disconnect when Sunny Boy production exceeds loads + charging? Or Sunny Boys operating zero export (which I would expect to have an issue deciding what is exactly zero, a problem when grid disconnected.)

Or PV & SB not yet installed?
1716121226719.png
I do not have the PV and SB installed, yet. I am getting a tree removed this week and I will begin installing the mounts on my roof, followed by the panels.

We will see if I need to adjust settings further once the SBs and PV system is installed. I've got a decent-sized honey-do list so I have to sprinkle in solar project as often as I can :)
 
Back
Top