Adding more panels to a builder installed Sunpower system

[Danimal86]

I'm kicking myself in the butt for not maxing out our solar option back in 2016 when our house was being built. The builder installed a 2kw (i'd have to dig up the paperwork to confirm) system that uses a Sunnyboy SB 3000TL-US-22 inverter and 5 panels on the roof of the second story (west facing). Looking at the sunpower app, we usually generate around 0.9kwh at peak during the day (this is August between 2-3pm). Seems like there's a lot of room left on the table.

I was looking at the data sheet for the inverter and saw that it has two inputs.


I'm not comfortable going up on the second story and messing with the roof, but we have a alumawood patio cover that starts getting sun around noon (back side of the house, west facing) thats about 25' wide and 10' deep.
I'm always looking around facebook marketplace and i see used panels for fairly cheap. For starters i'd add around 1k - 1.5k of solar to the system, figuring that that would get me around 2kwh production in ideal conditions. Most likely, since i'm a tinkerer....i'd keep adding until i get to the 3kwh.
Seems like i'd need 3-5 panels to get me going depending on the Vmp of the panels to get me over the 150v start voltage. Sunpower panels seem like they have the highest Vmp, i have local people that sell 320w sunpower panels for $100 (Vmp 55), so for around $500 in panels i could probably be close to my goal of 2kwh.

As far as the installation and connection, i'd probably use some sort of a track for the panels on the patio cover so that the weight would be distributed evenly (dont want to exceed 200lbs) and i probably will just leave them up for spring through fall and then take them down for winter since it can get pretty windy here. For connecting to the inverter I was thinking about adding a dc rated breaker inbetween the panels and inverter. Not really sure about how i would run the wires, probably try to have some sort of shielding on them but would rather not run conduit on the side of the house. I guess then just connect it to the second MPPT. Seem reasonable?
I'd love to hear some input if this seems like a good idea or i'm off my rocker. I'm also a little concerned with NEM 3.0, i'm not sure how anyone would know that we've added solar, we never dip into the negative for power usage.

 

[chrisski]

Seem reasonable?

Seems doable for the most part unless there is permitting issues.

but would rather not run conduit on the side of the house. I

The builder I went trenched with conduit. Prior to running cable in the conduit, an inspector would show up.

just leave them up for spring through fall and then take them down for winter since it can get pretty windy here.

To me that seems like a bad idea. Around hear wind speed is almost always calm but the freak wind storm or squall can come any time of year.

=================
May be more practical to have Sunpower install more panels and a better inverter. Unfortunately that is $15k per 5 kWh locally. To top that off, sunpower is having some financial troubles. I wonder how hard it would be to get a second contractor to expand this.

 

[Hedges]

I think about 4kW (STC) of panels would peak at the 3kW inverter rating.
I think about 6kW (STC) of panels, two 3kW strings of different orientation.
Since Sunny Boy has 2 MPPT, each can take one string.
It is also OK to wire two strings in parallel, would operate around peak for extended time.

It is a Sunny Boy; feel free to over-panel further. But understand Voc (and that it increases with cold weather), don't exceed hard voltage limit. Current limits are more like guidelines. Wattage limits are like suggestions.
With too much current or wattage on a single MPPT, Sunny Boy will limit. You get more peak power with array divided onto two strings for two MPPT. Two different orientations paralleled into one MPPT can work well, so see how many panels physically fit, what orientation, and design array to maximize production. Could be something like 3s2p into one MPPT, 3s2p into another MPPT, depending on wattage etc.

Santan Solar and various eBay sellers sometimes have SunPower panels.

 

[Danimal86]

Seems doable for the most part unless there is permitting issues.

The builder I went trenched with conduit. Prior to running cable in the conduit, an inspector would show up.

To me that seems like a bad idea. Around hear wind speed is almost always calm but the freak wind storm or squall can come any time of year.

=================
May be more practical to have Sunpower install more panels and a better inverter. Unfortunately that is $15k per 5 kWh locally. To top that off, sunpower is having some financial troubles. I wonder how hard it would be to get a second contractor to expand this.

Hey thanks for the response. Aiming for a DIY solution without having to pull a permit/get inspections.
Regarding the abitlity to remove the panels, I guess it would be more of the ability in case we get one crazy wind storm that comes through. Usually it maxes around 10-20mph wind, but 2 decembers ago we had a crazy wind storm that came through that gusts were 60+mph.....i'd pull them for those type of storms since they wont be bolted down.

Only way it would make sense for us to upgrade the entire system is if we bought a couple EV's and went with a ton of panels and batteries, but i dont see that happening anytime soon.

 

[Danimal86]

I think about 4kW (STC) of panels would peak at the 3kW inverter rating.
I think about 6kW (STC) of panels, two 3kW strings of different orientation.
Since Sunny Boy has 2 MPPT, each can take one string.
It is also OK to wire two strings in parallel, would operate around peak for extended time.

It is a Sunny Boy; feel free to over-panel further. But understand Voc (and that it increases with cold weather), don't exceed hard voltage limit. Current limits are more like guidelines. Wattage limits are like suggestions.
With too much current or wattage on a single MPPT, Sunny Boy will limit. You get more peak power with array divided onto two strings for two MPPT. Two different orientations paralleled into one MPPT can work well, so see how many panels physically fit, what orientation, and design array to maximize production. Could be something like 3s2p into one MPPT, 3s2p into another MPPT, depending on wattage etc.

Santan Solar and various eBay sellers sometimes have SunPower panels.

Thanks for the info. Good to know that there's some headroom without going over the Voc (looks like 600v in my case). I dont really know how the current 5 panels on the roof are wired up. I'd think probably straight series to get over the Vmp?

I'd imagine that i'd probably wire up all the panels in series to try to get over the voltage trigger for the mppt. I dont really have a ton of weight to work with, it seems like most of these pannels weigh 40-50lbs each so i probably would be limited to 5-6 total before i worry about overloading the patio cover (weight will be distributed evenly). I did think about going with some flexible panels since they weigh much less, but would be cost prohibitive since most i've seen are 100w-150w and seem to run $100+

I did check out ebay/Satan Solar, seems like most you have to buy pallets, so probably would work too well unless i get some neighbors that want to do the same thing, or sell them on FB Marketplace.

As far as wring them, i was figuring i'd use some 10g wire and put a DC rated breaker between the panels and sunny boy...anything else other than panel connectors?

 

[Hedges]

5 panels would be in series. Whatever Voc adds up to, multiply by 1.16 for conservative estimate of max in cold. Or do more careful calculation.
If you add many, could be two strings. All in one string need to be same or very similar orientation.

Flexible panels I hear die in a very short time. Rigid frame monocrystaline panels are the way to go

Wire should be PV wire where exposed (tough, UV resistant, 1000V rated.) Inside conduit, use THHN/THWN-2 or PV wire.
You can buy ready-made PV cables with something resembling MC4 connectors. Mix-n-match of brands should not be done, doesn't meet UL, have been known to cause fires. Only identical model or UL listed pair of brands tested together.

I paid $295 shipping from Santan Arizona to San Jose one month ago. That was a pallet of 25 panels. I drive there with my pickup; maybe $100 extra if they deliver to you?

I see four SunPower listings right now:

Shop Refurbished Solar Panels | SanTan Solar

Shop Filters Shop / Shop Products / Search results for “sunpower” Quickview 10AWG PV Cables $7.50 – $121.50 Select options Quickview 10KW 120/240 Sungold w/5KW Solar 10KW Battery Kit $7,500.00 Add to cart Quickview 11.3KW QCell Solar Panels w/ Growatt 10KW Inverter Grid Tie Tigo Kit $7,450.00...

www.santansolar.com

e.g. $125 for 435W panel "Max power current: 5.97 A"

If connected in series with your existing panels, needs to be same/similar current. Will operate at the lowest current of any panel in the string.
What are specs of existing ones?

$125 x 5 + $295 + $100 = $1120, plus tax for 2175W

Buy one or two extras, in case one gets damaged, and for expansion plans.
PG&E allows 1kW increase over what was originally authorized. You might later shop on eBay for a 4kW Sunny Boy. About 5kW to 5.5kW (STC) of panels would fully load that, assuming same orientation. About 7.5kW to 9kW of two orientations, maybe as four strings into two MPPT, would be the most it could utilize well.

Older model 4000US, may not have AFCI, too expensive: https://www.ebay.com/itm/126030578372

Newer model 3.8kW -40 series https://www.ebay.com/itm/305310344561

For a 100A breaker panel and main breaker, 3.8kW PV inverter, 16A continuous through 20A breaker, is considered max. But I wouldn't worry about 4.0 kW, not likely to trip breaker.

I prefer to pay $0.10/W for older Sunny Boys.

I doubt 2000 lbs distributed would be too much vertical force unless horizontals are 2x2 wood. Make sure verticals are braced for earthquake and wind resistance.

 

[Danimal86]

5 panels would be in series. Whatever Voc adds up to, multiply by 1.16 for conservative estimate of max in cold. Or do more careful calculation.
If you add many, could be two strings. All in one string need to be same or very similar orientation.

Flexible panels I hear die in a very short time. Rigid frame monocrystaline panels are the way to go

Wire should be PV wire where exposed (tough, UV resistant, 1000V rated.) Inside conduit, use THHN/THWN-2 or PV wire.
You can buy ready-made PV cables with something resembling MC4 connectors. Mix-n-match of brands should not be done, doesn't meet UL, have been known to cause fires. Only identical model or UL listed pair of brands tested together.

I paid $295 shipping from Santan Arizona to San Jose one month ago. That was a pallet of 25 panels. I drive there with my pickup; maybe $100 extra if they deliver to you?

I see four SunPower listings right now:

Shop Refurbished Solar Panels | SanTan Solar

Shop Filters Shop / Shop Products / Search results for “sunpower” Quickview 10AWG PV Cables $7.50 – $121.50 Select options Quickview 10KW 120/240 Sungold w/5KW Solar 10KW Battery Kit $7,500.00 Add to cart Quickview 11.3KW QCell Solar Panels w/ Growatt 10KW Inverter Grid Tie Tigo Kit $7,450.00...

www.santansolar.com

e.g. $125 for 435W panel "Max power current: 5.97 A"

If connected in series with your existing panels, needs to be same/similar current. Will operate at the lowest current of any panel in the string.
What are specs of existing ones?

$125 x 5 + $295 + $100 = $1120, plus tax for 2175W

Buy one or two extras, in case one gets damaged, and for expansion plans.
PG&E allows 1kW increase over what was originally authorized. You might later shop on eBay for a 4kW Sunny Boy. About 5kW to 5.5kW (STC) of panels would fully load that, assuming same orientation. About 7.5kW to 9kW of two orientations, maybe as four strings into two MPPT, would be the most it could utilize well.

Older model 4000US, may not have AFCI, too expensive: https://www.ebay.com/itm/126030578372

Newer model 3.8kW -40 series https://www.ebay.com/itm/305310344561

For a 100A breaker panel and main breaker, 3.8kW PV inverter, 16A continuous through 20A breaker, is considered max. But I wouldn't worry about 4.0 kW, not likely to trip breaker.

I prefer to pay $0.10/W for older Sunny Boys.

I doubt 2000 lbs distributed would be too much vertical force unless horizontals are 2x2 wood. Make sure verticals are braced for earthquake and wind resistance.

Dang i hadn't seen any sunpower panels go that high wattage. Looks like it would fit the bill nicely! I just saw a post on SanTan's Facebook page that they were selling used sunpower 435's for $95, i tried using the code they gave but it looks like it expired. I would have instantly pulled the trigger at that price. Looks like you have to buy a minimum of 10 though :-(

I have no idea what the existing panels are on the roof that the builder put in. I think it was a 2kw system, but i remember that paperwork i got from the builder was just a single sheet without much info. I could fly my drone up and take a close up picture, but i'm not sure how helpfull it would be. There are 5 pannels up there, not sure if they had 400w panels back in 2017...it could very well be a little less than 2kw system. I looked back at the solar output history and it looks like peak output is around 0.9kwh-1.0kwh in the middle of summer here in Sacramento.

We use are lucky and get SMUD for power, i need to look to see what they allow...if its like PG&E and allow for 1kw over what was authorized, would that mean that (assuming its a 2kw system) that i could get up to 3kw of "actual" output? If so, that would probably be plenty, since currently i'm only tickling 1kwh. If i were only able to add 1kw worth of panels, then i'm not sure it would be worth it

Patio cover should be plenty sturdy. its one of those alumawood deals (steel posts i believe), was professionally installed and inspected. We had two ceiling fans installed and they ran reinforcements for where the fans will be.

 

[Hedges]

Climb up, hold your cellphone underneath, and snap a picture of the label.

After you figure out what you want, call Santan and see if they'll give you a break. You can tell them you got referred by this forum, just too late for that deal.

You don't want to spend $950 or $1250 on ten panels, after you paid someone HOW MUCH to install 2kW of PV with 3kW inverter?

Don't know if they went by PV panel CEC rating (less than STC), or by inverter rating. Hopefully 3kW inverter. You can overpanel it without exceeding 3kW output, upgrade to 4kW.

SunPower made bigger and smaller panels with same cells, same amps. That's what you want to match in series.
For parallel, match string voltage.

 

[Danimal86]

Climb up, hold your cellphone underneath, and snap a picture of the label.

After you figure out what you want, call Santan and see if they'll give you a break. You can tell them you got referred by this forum, just too late for that deal.

You don't want to spend $950 or $1250 on ten panels, after you paid someone HOW MUCH to install 2kW of PV with 3kW inverter?

Don't know if they went by PV panel CEC rating (less than STC), or by inverter rating. Hopefully 3kW inverter. You can overpanel it without exceeding 3kW output, upgrade to 4kW.

SunPower made bigger and smaller panels with same cells, same amps. That's what you want to match in series.
For parallel, match string voltage.

We've got a 2 story house....would have to grab a 24+' extension ladder to be able to hop up there.

Yeah I could save a few/sell the others if need be from the 10pk.

I found on the smud site:
Can I increase the size of my solar electricity system?
For customers on the Solar and Storage Rate (SSR), SMUD will allow your system to be sized up to 110% of the last 12-month kWh consumption or up to 120% if battery storage is added on the premises. For existing NEM1 legacy customers, if the system size is increased by more than 10% of generating capacity originally approved, or 1 kW, whichever is greater, or exceeds 110% of generating capacity originally approved, you must move to the SSR rate schedule and submit a new Interconnection application.

So if i read that right, i can increase a max of 1kw from what was originally approved. I reached out to SMUD to see what we are approved for, waiting for a call back. Hopefully its 3kw.

 

[k490]

My understanding is that California builders are required to install solar is that how they do it throw up a few panels call it good? 2KW is what someone would put on a class A motorhome. Surprised they don't use microinverters. I would get a get a new design from greenlancer and start over with a new interconnect agreement. You could hire out to someone to install the panels you don't have to hire a contractor. You would be your own contractor just paying someone to do the labor get on the roof. Find a local electrician who willing to help if you have an approved permit from AHJ I bet you could find someone. If it were me, I would not lose mount anything on a patio cover you could be out of town and a windstorm shows up at the wrong time 40 lbs glass panels flying into your neighbor's yard.

 

[Danimal86]

So i heard back from SMUD. Bad news....first of all, i was off on the idea of it being a 2kw system. Its a 1.18kw baby system.
They also informed me that any adjustment to the solar system would trigger a change over to the new NEM system. I never really dug into what all that means when it was the hot topic last year, but i guess it really only matters is you produce more than you use.

That kinda sidelines the hopes of just a quick and dirty diy setup.

 

[k490]

So i heard back from SMUD. Bad news....first of all, i was off on the idea of it being a 2kw system. Its a 1.18kw baby system.
They also informed me that any adjustment to the solar system would trigger a change over to the new NEM system. I never really dug into what all that means when it was the hot topic last year, but i guess it really only matters is you produce more than you use.

That kinda sidelines the hopes of just a quick and dirty diy setup.

Do they have a connection into your inverter? I thought I read somewhere that California requires that maybe not back in 2016 if not how are they going to know what your doing. I would just buy some rails and mount them properly make it look professional that way doesn't look DIY. Guy posted here he was caught after some solar contractors noticed he had some panels just laid on his roof that also was in CA. He had to pay $1000 fine.

It's the same situation here in AZ if your under a grandfather and you make changes to your system lose that grandfathering. We used to have 1-1 Net metering which is dumb because if you installed 200 watt panels 13 years ago and several go dead where do you find same panels to replace them with. It's just another trick utilities use, and the solar contractors don't tell customers about that. If I had to guess I bet lot of people who are under a grandfather just replace with larger panels, and inverters no one knows the difference.