Newbie to solar gotchas?

[JoeBinotto]

@CycloneFW, question did you only pay $10,500 (net) for your 28 panel system? That is an amazing price!

[CycloneFW]

I ideally want to use the 225 amp panel as well because, if all goes well, I plan to expand the system next year. I need about 15 kW to offset my usage and Duke allows net metering for you to 20 kW, but their rebate is only up to 10 kW. So I’m doing the 10 now and thinking of another 5 next year. I would imagine having line side taps with two arrays wouldn’t be fun.

[Ampster]

I would go for the bigger panel even if you have to derate it. I like the simplicity of not having a line side tap but that is not a professional opinion.

[CycloneFW]

So another question. I imagine my county permitting and inspection office would be my AHJ. They have given their blessing to installing the 225 amp panel even with it having a 225 amp main breaker. My electrician called Duke Energy though and the admin office said they don’t have documentation on what my transformer feed wiring size is to my meter, to see if it would support 225 amp.

When poking around the Internet with some searches, I see some posts about the meter being rated 200 amp continuous and up to 240 amp, so going from the meter to the main service panel with 225 wouldn’t be a problem. Does that generally sound correct to you folks?

Ideally I’d like to put in the 225 amp panel with its factory 225 amp breaker, as I’m already paying a premium for the panel itself. If I wanted to derate to a 200 amp main and use this panel for the 225 amp bus, that is another breaker to buy and I’d be tempted to just use the 200 amp panel I got (for $80 less than the 225 amp panel) and have my installer do a line-side tap (they already had planned on this before I decided to do the panel upgrade).

[bob-n]

You're right. Two protectors is better than one. But the MNSPD600 is not right for your home. You need the MNSPD300AC for protecting the 240VAC mains.

"The MNSPD-300-AC can be used on120/240 VAC split-phase or two legs each on 208 VAC circuits. The MNSPD-600 is designed for high-voltage grid-tie PV arrays, or two legs each on 480 VAC circuits."

[CycloneFW]

So things are starting to come together. I am still a go with the installer, but I pulled off the panel upgrade and go with my own electrician to save almost half of the panel upgrade cost. I got two panels just in case of hiccups, as one is a Eaton 200 amp 40-space 50-circuit BR-style panel (matching my existing panel, so I could reuse my newer circuit breakers if I wanted to) and the other is a Eaton 225-amp 42-space 84-circuit BR-style PON panel with a copper bus. I wasn't expecting it to have a 225 amp main, but that's what is on there. Got all new circuit breakers as well with the plan being to use new breakers vs. the tandems to avoid any concerns b/c my older house shares neutrals across multiple circuits. Wouldn't want a goof to actually put both legs of service to the same neutral via the circuit breakers. My electrician filed for the permit and expects that he can install it next week.

Meanwhile, rerouting the vents is technically possible as the room is there to do so. However, it is beyond what I can do that the installer doesn't feel it would be worth the effort and the extra cost they would charge me. They have meanwhile revised the panel layout, putting a top row of horizontal/landscape-oriented panels with two rows of vertical/portrait-oriented panels beneath on the main roof. The revised design has them using a Soladeck to penetrate the roof beneath the top right panel, exit the side to get to the garage roof, and come down from the soffit behind the house on the exterior of the home. I've asked them to change that to avoid exterior conducting. Right where they want to put the Soladeck penetration, there is a hollow column that leads from the roof beside the master bedroom closet to the main floor. From there, penetrating outside gets you to the garage and coming down there gives you access to a path into the basement. This would prevent any conduit outside except for a small run around one of the vents. I suspect this would mean the garage setup would have a penetration as well. In their design, I suspect they were going up the conduit to the roof and then down the soffit, but am unsure.

I verified that if I do not get permitting approval for the solar install by there design and we cannot make it work, my deposit is refunded to me.

Now for an actual question. I ordered a Midnite Solar MNSPD-300-AC to install in the new panel. I already have an Eaton whole house surge protector on the old panel that I can reuse, but I figure two doesn't hurt. However, what arrived was the MNSPD600. My understanding is that on the 300, AC vs. DC is just how the leds are wired (correct me if I am wrong please). Would I be able to use the 600 for my intended purpose, or should I got through the process to get a 300-AC to put in? The 300 lists a clamping voltage of 775v and the 600 lists 1290v. I would imagine this means more surge would come through before the SPD shunts to ground?

[peakbagger]

To confirm my thoughts, my suggestion was reroute the vents inside the attic. As long as the lines are sloped upwards and the line sizing was not borderline to begin with running vents to near the ridgepole usually improve the flwo characteristics. I do not think a typical solar installer would have the capabilities or interest to do this, in order to be competitive they need to get in an out using a inventory of stock parts. Moving vents is custom. A typical Home Depot has the parts you probably need. The biggest hassle is working up there, its hot and dusty and in many home you have to stand on trusses.

[CycloneFW]

There are methods to extend plumbing vents underneath and beyond the panels. Solar panels should not be mounted over any vents that the not been extended. Bathroom Vents are too big to be extended under the panels and as @peakbagger said they could be rerouted to near the ridge or the north facing roof.

Thank you @peakbagger and @Ampster , I will explicitly ask about rerouting the vents, if possible. They haven’t come for the on-site survey yet, so I will bring it up with that crew as they gather the doc for the designer.

I appreciate everyone’s help with these things. It seems I’ve done a good job covering the big details, but these small details/nuances are what I missed up front. Exactly why I created this thread!

[Ampster]

.........
Are you saying to shift the bathroom exhaust vents to the ridge? I should mention that the Sunpower installer providing the second image in the Op said they would reroute, if possible. The proposed setup assumes they could. Another installer said, depending on the height, they could install over the vent.
........

There are methods to extend plumbing vents underneath and beyond the panels. Solar panels should not be mounted over any vents that the not been extended. Bathroom Vents are too big to be extended under the panels and as @peakbagger said they could be rerouted to near the ridge or the north facing roof.

[CycloneFW]

Any chance you have access to the attic so you can re-pipe what I presume are stack vents up to the ridgepole?

Do not forget about installing surge protection devices on the incoming utility line and on the line coming into the house from the array. I think the Midnight Solar SPDs have the best reputation. It will not save you from a direct strike but may from an nearby strike

There is crawl space access to the attic on the house and full standing access to the attic on the garage. I have three exhaust fans in the house, one for each bathroom. I suspect the two upstairs share the vent surrounded by panels, the one near the center ridge (which is using a ridgevent) is for the downstairs bathroom (it is in the center of the house), and the one closer to the edge, which basically above the master bathroom, is for the waste drain? If not, then those each are for one of the bathrooms, but then I don’t know where the waste line is getting an air intake from.

The roof was redone 5 years ago and the old vents were replaced with these newer ones. They weren’t relocated though, if I recall correctly. There used to be one of those balloon-looking oscillating vents up there, but that was replaced with the ridgevent.

Are you saying to shift the bathroom exhaust vents to the ridge? I should mention that the Sunpower installer providing the second image in the Op said they would reroute, if possible. The proposed setup assumes they could. Another installer said, depending on the height, they could install over the vent.

I do have a whole-house surge suppressor in the panel. I suspect you are talking about a different device though? I saw on an off-grid YouTube video someone putting on DC suppressors at his combiner boxes and then another one at his inverter. I don’t recall if this third one was DC or AC. Are you suggesting something like that?

[peakbagger]

Any chance you have access to the attic so you can re-pipe what I presume are stack vents up to the ridgepole?

Do not forget about installing surge protection devices on the incoming utility line and on the line coming into the house from the array. I think the Midnight Solar SPDs have the best reputation. It will not save you from a direct strike but may from an nearby strike

[CycloneFW]

Phil,
1. Yeah. All of them (except 1) actually originally quoted above 10 kW, but I asked for a 10 kW cap to maximize the utility rebate. But even after that, I was surprised by the fourth row on the garage roof.

I had forgotten that one of the other proposals included measurements. I'll punched this into SolarEdge Designer using these measurements and saw there is a good bit of room before the edge of the garage roof edge. There will be more than 18" to the edge and thus, no overhang.



2. That is a VERY good question. I hadn't even thought about asking that. I will make sure to ask for this explicitly. Either way, I am the type who reads every single page in major contracts (like my 104 page refinance). I will be doing that with the purchase agreement.

3. Their website has a large number of images of prior installs and they have great reviews on EnergySage. However, the images are only one per project and nobody I know personally has used them. I can ask if they have more sample project images I can look through. I put a few into this Imgur album if anyone wants to look at them. Meanwhile, they explicitly mention "our installers and electricians document every step of the installation process with pictures and videos", provided their GC license number, state they are NABCEP Certified, only use #6 copper, etc.

4. I had read some of the threads about SolarEdge monitoring here. I would definitely push to have Owner + Admin (even if only read-only) access. I've already registered with SolarEdge as an installer. Along those lines, they include the consumption meter, so I'll have the high-level data SolarEdge provides for their system.

5. They use Aurora to mock up the setup and evaluate the expected sun-hours. The sent me a video 3D tour of the property.

[oregon_phil]

To add to the already excellent advice given, I have the following additional thoughts:

1) It seems like the solar estimators (sales person) try to cram as many panels in the estimate as possible only to have the technical layout person come back with reality due to codes and regulations.

It looks like the first layout has panels almost overhanging the gutter line. I had my installer move the panels back from the gutter line about 18" so the rain doesn't run down the panel, over the gutter and onto the ground.

2) The in house designer designs the layout for you to sign off. I paid this fee after it went though permitting. What if you sign off on the document, pay them a fee and then it gets rejected at permitting?

3) I would want to know how all the particulars of roof, wall, etc penetrations into my house. What is it going to look like? Do they have examples?

4) I would ask for full access to whatever app/program as your installer is using for the inverter.

5) I had an estimator use an app (Helioscope?) where it pulled in google earth data (picture location, time date, etc) that showed tree shadowing for a particular date time and location. They he manipulated the date and time to show shadow movement through the day for different dates (winter, summer). It did help visualize shadow movement for different times of the year. You can do the same thing in SketchUp if you are good with CAD and pay a little bit of money for the app.

[CycloneFW]

Whew, lots of info here. Going to try and break it down to not get lost in a wall of text.

It looks like several trees near the house have to go.

Also, I would do the meter upgrade "critical Loads " panel

One installer said nothing about removing trees. She was out of consideration immediately. The other wouldn't estimate production w/o the tree, so he went out of consideration. The remaining three all said to remove the big tree, with the statement that when doing the on-site measurements, they will confirm if others needs to be trimmed/removed. I am open to that, but we will see what they advice is. I trim back the trees every few years already and just did so last year, so I may be good with just removing the one and trimming the others more regularly.

I thought so on the panel. Time to bite that bullet and at least get aa 26% discount on doing it.

Any PVWatts modeling is without shading unless you plug in an estimate by modifying the system loss parameter.

I'd invest in a chain saw and get rid of the trees, but that's opinion.

From the cartoons, and depending on their height, it looks like some of the roof penetrations may shade some of the array. Perhaps more importantly, if the first cartoon is correct in its roof penetration locations, the Sunpower cartoon will have has panels either covering vents or the vents assumed moved. Covering vents is not a good idea.

Help avoid the Dunning-Kruger syndrome by getting good and straight information that'll filter the hearsay and conflicting info from unvetted sources - usually with skin in the game. Start with a free download of a slightly dated version of " Solar Power Your Home for Dummies"., or a new hardcopy version for ~ $25 @ bookstores. Learning buzzwords and anecdotal junk without a grasp of the basics is like trying to get into an elevator that's already gone up 5 ft.

Yeah, I put in a system loss value in there, but I likely didn't put in enough of a loss compared to what the installers worked up. I trim the lower portion of the trees myself regularly, and high pros for more every few years. I just did the lower trimming in June. I've been reading that. I've read up to Chapter 5. So far, a good read, but nothing I wasn't already aware of thanks to being a science nerd. Hence the concern about Dunning-Kruger syndrome! The next few chapters should be most interesting.

I think that the installer is assuming that the panels go up in August or September, but the power company may not get around to doing their meter swap until October. There is a normal power meter and a "netmeter". When you install solar panels, the power company will take out your normal meter and install a netmeter.

Gotcha. I didn't realize that getting my PTO could be done before a bi-directional meter is installed. That would explain how the installer's comment would work.

On your power bill, the power company will have three charges: meter rental (fixed fee), cost for energy you use (going in), and credit for energy you made surplus (going out). Rates vary, but the meter rate is probably in the $10 to $25 per month range. Energy going in costs more and energy you send out gets credited less. Sorry for being vague. You need to check with Duke to get the exact netmeter rates in your town.

Familiar there. I can remain on my same RE schedule listed in the Op. A friend sent his January bill so I can see the differences. He is on the RS schedule, but the only difference between the two is he pays/gets a higher $/kWh that I would. I am eligible to switch to RS if I wanted to, but since I will produce less than my usage nearly year-round, I plan to stick my cheaper rate schedule. Basically, $14/mo + around $0.08/kWh + tax.

My buddies bill:

As to the payback time, the smaller the install, the less you pay up front, so likely the sooner it pays back, but the less it produces. Opinions on the optimum size vary from 110% to 130% of your current usage. You can find your current usage by looking at your power bills over the past year. Many power companies make that historical information available easily on the web.

I'm actually only going to do around 60% of my usage because my utility rebate is capped at 10 kW annually. Even with the lower credit next year, it makes more sense to spread the rollout over two years if I want a larger system (we'll see how this goes first).

Trees are always a problem and GET WORSE with time. They grow roughly 1.5' to 2' per year, depending on the species and climate. So even if you have very little shade from the trees now, you might have a lot in the future. Large trees are more expensive to cut than smaller ones, so get to them as soon as you can. I believe that you can include the cost of tree removal in your federal tax credit calculation, if it directly benefits solar power, but I am not a tax professional. Verify that with a tax professional.

Verified. Any tree removal and panel upgrade costs will be deductible through the ITC. I was already wanting to remove this tree, but the lightbulb hadn't gone off that the larger the tree, the more it would cost (within only a few short years). This tree was seriously trimmed back 10 months ago. Now I want it removed even if I didn't do solar.

If your roof is worn, STOP. It is false economy to install solar panels on a roof when replacement is due soon. Reroofing with solar panels will add >>$1k to the roofing bill, perhaps >$4k depending on the exact situation. Again, please forgive me for being vague. Each situation and each contractor is different.

No problem. I looked into solar five years ago when I got my new roof. The financials then just didn't make it worthwhile. Including the cost of removing the tree, I was looking at over a 25 year payback due to local pricing then being (retail) $4/watt.

You didn't mention the hardware that the contractors are proposing. We see three general types of installations:
1) String inverters.
2) String inverters with optimizers.
3) Microinverters.

Sorry, that might have gotten lost in my long opening post. SolarEdge SE10000H (HD Wave) string inverter with SolarEdge P370 Power Optimizers.

[bob-n]

Here are some thoughts. I hope that they help.

You wrote: Oddly, the installer said “Between initial installation (August) and final activation with Duke (October) you are still able to generate and use your solar power on-site. The only thing you can't do is sell excess power back to Duke (until you fully activate in October).” I don’t understand how that works.

I think that the installer is assuming that the panels go up in August or September, but the power company may not get around to doing their meter swap until October. There is a normal power meter and a "netmeter". When you install solar panels, the power company will take out your normal meter and install a netmeter.

The normal meter measures energy. It's clueless whether you make power or you use power. It just measures power x time and calls it energy.

The netmeter measures power going out and separately measures power coming in. So for bright sunny days when no one is home, you're making lots of power and using very little. That means you're sending lots of power out to the neighbors. The netmeter will record all of the energy going out in the "going out" accumulator. At night, when you're using power and not making power, all of the energy you use gets recorded in the "coming in" accumulator. If you're making 4000W and using 2000W, then you are sending 2000W out and recording it in the "going out" accumulator. If you're making 100W and using 1000W, then you are consuming 900W from the power company, so 900W gets recorded in the coming in accumulator.

On your power bill, the power company will have three charges: meter rental (fixed fee), cost for energy you use (going in), and credit for energy you made surplus (going out). Rates vary, but the meter rate is probably in the $10 to $25 per month range. Energy going in costs more and energy you send out gets credited less. Sorry for being vague. You need to check with Duke to get the exact netmeter rates in your town.

As to the payback time, the smaller the install, the less you pay up front, so likely the sooner it pays back, but the less it produces. Opinions on the optimum size vary from 110% to 130% of your current usage. You can find your current usage by looking at your power bills over the past year. Many power companies make that historical information available easily on the web.

Trees are always a problem and GET WORSE with time. They grow roughly 1.5' to 2' per year, depending on the species and climate. So even if you have very little shade from the trees now, you might have a lot in the future. Large trees are more expensive to cut than smaller ones, so get to them as soon as you can. I believe that you can include the cost of tree removal in your federal tax credit calculation, if it directly benefits solar power, but I am not a tax professional. Verify that with a tax professional.

In addition to PVWatts (great site!), fanatics will survey their property with a shade-measuring tool, such as the cellphone app scanthesun. It's not trivial to use, but there are youtube videos that walk you through it. Your installer may also do that for you.

If your roof is worn, STOP. It is false economy to install solar panels on a roof when replacement is due soon. Reroofing with solar panels will add >>$1k to the roofing bill, perhaps >$4k depending on the exact situation. Again, please forgive me for being vague. Each situation and each contractor is different.

12 year payback is in the same general range other see. Some people do the installation themselves and cut that down to 4-6 years. But that means working on a roof, doing high-power electrical work, and pushing your comfort zone.

You didn't mention the hardware that the contractors are proposing. We see three general types of installations:
1) String inverters.
2) String inverters with optimizers.
3) Microinverters.
#1 is cheapest, #3 most expensive. #1 has a weakness in that shade on any one panel will significantly reduce output from your total system. #2 and #3 reduce the shade problem. Shade comes from trees, clouds, chimney, vents, and other things. They all reduce your production. #2 and #3 are better in terms of shade, but some people believe that they are less reliable because they require putting electronics on the roof. So far, the statistics I've seen have shown microinverters are more reliable than panels so this doesn't worry me, but others here are strongly against microinverters. Please don't quote me on this, but the added cost for microinverters is VERY roughly $50 per panel extra in material cost. That's not a big percentage of the total job, so once you decide what you want, make sure your installer gives you your preference.

I hope that this helps. Please continue to ask questions here.