Evaluating a quote for 9kw grid-tie solar install

[7acres]

We got quotes back yesterday from a local company that's been in business for 40 years and of good reputation. Of the 4 variations of proposals they provided one of them hits the sweet spot for what we are in the market for. Two of the quotes were based on an 11kw system; one for roof mount and one for ground mount. They were outside of what we feel comfortable paying for.

Of the two 8.96kw variations the ground mount seemed to be the best route. Our roof faces west. The ground mount was projected to be about 46% more efficient than roof mount while costing only 19% more. So I'd like your opinions on the ground mount install they are proposing.

Panels: CanadianSolar CS6K-280M (Quantity 32)
Inverter: SMA / SPR Sunny Boy 5,000TL-US (Quantity 2)
w/ WebConnect data exchange portal
Ground Mount System: Schletter FS System Ground Mount System
Meter: Certified utility revenue grade meter

The cost breakout is basically:
$35,750
-$10,725 (30% Federal tax rebate)
-$8,937 (25% State rebate)
-$7,168 (Utility rebate after 20% taxation)
____________
$8,920 Net cost after credits/rebates, etc.

This system is projected to offset 68% of our power bill and pay for itself in 5 years. My wife and I are loving these numbers. Is there anything here that would make you nervous if you were in my shoes? Anything I need to press them for further discussion on?

 

[maple1]

Holy wow on those rebates. I only wish we had incentives like that here.

 

[7acres]

Another tid bit that I was happy to hear...

Five years ago I installed a Generac 17kw propane whole house generator. They explained that their install is essentially supplementing grid power. When the grid goes down so does the solar array (anti-islanding). From my generator's point of view it's the same as normal loss of grid power. My generator will automatically fire up and power the house.

They don't need to do anything inside the house or even touch my main 200 amp breaker box. Everything they do will be outside at the breaker panel attached to the meter. I trust that's all true. If it is my generator still serves it's original purpose.

 

[DBoon]

Nothing they quoted would make me nervous.

I paid about $5/watt for a 5.3 kW ground mount about 3 years ago. I specified US made panels (increase in cost). If I had to do it over again, I would get frameless panels since the snow doesn't slide off these too well on its own. Otherwise, I like what I have.

I think the ground mounts will run about $1/watt more than a roof mount (guessing). $4/watt seems pretty reasonable (before incentives). I'd probably go with an 11kW if I could afford it if 9 kW only satisfied 2/3 of my bill, but not sure on how your net metering works (monthly or yearly) or what else may impact this.

 

[peakbagger]

The only thing that sounds slightly suspicious but may be legit is the statement that they don't need to touch your 200 AMP panel. Generally a 200 amp panel is the main panel with the main breaker and the outside meter panel doesn't have a breaker (unless its a mobile home). It may just be a regional difference or a special installation with a breaker at the meter. If there is a main breaker at the meter its not a problem but if they are doing a line side tap in the meter box, most utilities do not allow a tap in the meter panel. The usual fix for this is to install a separate panel between the meter panel and the main panel for the tap, the only hassle is they need to pull the meter but with your generator, you can just run on the generator while the power is out.

Sounds like a great deal. At that price I would probably but in bigger array and buy an electric car.

 

[jebatty]

I have Schletter FS 2Vx13, high load, ground mounts. These are top of the line IMO, good choice. In my area current bids are coming in at around $3.50/watt for ground mount systems.

 

[7acres]

Nothing they quoted would make me nervous.

I paid about $5/watt for a 5.3 kW ground mount about 3 years ago. I specified US made panels (increase in cost). If I had to do it over again, I would get frameless panels since the snow doesn't slide off these too well on its own. Otherwise, I like what I have.

I think the ground mounts will run about $1/watt more than a roof mount (guessing). $4/watt seems pretty reasonable (before incentives). I'd probably go with an 11kW if I could afford it if 9 kW only satisfied 2/3 of my bill, but not sure on how your net metering works (monthly or yearly) or what else may impact this.

Our net metering works yearly. Power company settles up in March of each year.

 

[7acres]

The only thing that sounds slightly suspicious but may be legit is the statement that they don't need to touch your 200 AMP panel. Generally a 200 amp panel is the main panel with the main breaker and the outside meter panel doesn't have a breaker (unless its a mobile home). It may just be a regional difference or a special installation with a breaker at the meter. If there is a main breaker at the meter its not a problem but if they are doing a line side tap in the meter box, most utilities do not allow a tap in the meter panel. The usual fix for this is to install a separate panel between the meter panel and the main panel for the tap, the only hassle is they need to pull the meter but with your generator, you can just run on the generator while the power is out.

Sounds like a great deal. At that price I would probably but in bigger array and buy an electric car.

We don't live in a mobile home. But this is the panel on the back of the house. What you said about installing a separate panel between the meter panel and the main panel sounds like what they said they would do.

I love the electric car suggestion. For now that's quite a stretch from the budget standpoint. Honestly I didn't see myself as a solar panel guy when we were putting in the wood stove. I'm still kind of in denial. But I can't find any excuse not to do this.

 

[Where2]

We don't live in a mobile home. But this is the panel on the back of the house.

I've got a similar breaker panel on the back of my house (Square-D Homeline), and I'm not in a mobile home either. Mine happened to be there because I upgraded the service entrance back in 1998 and thought "If I'm replacing the meter can with one that needs an external disconnect for the fire department, why not install one with breakers in case I ever want to install new circuits outside?". When I installed my PV array, I still dropped a separate 8 breaker Square-D panel adjacent to it to use as a solar combiner panel and lock out-tag out box for the PV array. The PV combiner panel is decorated in red NEC compliance stickers.

 

[Longstreet]

Did you request the ability to expand the system later? 10kw of inverter rating is decently oversized, probably 15-20%. I'd have to look up the exact derating ratio again.

I personally would rather have one larger imverter than two small. Like an 8k.

 

[7acres]

Did you request the ability to expand the system later? 10kw of inverter rating is decently oversized, probably 15-20%. I'd have to look up the exact derating ratio again.

I personally would rather have one larger imverter than two small. Like an 8k.

I did not. Didn't know that was a wise thing to consider. So I can add another rack of panels in the future?

 

[peakbagger]

I like using two smaller inverters rather than one larger inverter. I think SMAs have two MPPT circuits for each inverter (at least some do). Two 5 KW inverters will have 4 mppt circuits so if there are any shading issues on part of the array its a good chance that 3/4 of the array will function. The SMA units also have the secure power supply feature so two inverters mean two SPS circuits.There is also something to be said for having a second inverter if one fails.

 

[7acres]

Good points. Reminds me... They offer a $600 warranty on the inverters. They said the chances an inverter will fail in the first, I think they said 10, years is very high. I'll have to get the specifics on that offer again. Is an inverter warranty a good idea?

 

[Longstreet]

I like using two smaller inverters rather than one larger inverter. I think SMAs have two MPPT circuits for each inverter (at least some do). Two 5 KW inverters will have 4 mppt circuits so if there are any shading issues on part of the array its a good chance that 3/4 of the array will function. The SMA units also have the secure power supply feature so two inverters mean two SPS circuits.There is also something to be said for having a second inverter if one fails.

I was just assuming because he was going ground mount he could pick a location without shading. I agree, if shading is expected to be a problem two inverters are the way to go. I generally prefer one only becuase you have half the chance of a failure. Yes you only lose half your output if you have a failure with two inverters, but you have failures twice as often, so in theroy it washes out even.

It's a minor detail with no right answer. I'm simply the kind of guy who thinks you should question these kind of things, just to make sure your installer has a well thought out answer. The answer itself isn't as important as confirming your installer understands what he is doing.

 

[jebatty]

Is lower price the main reason for selection of string inverters rather than micro-inverters on each panel? I have micros, and the monitoring shows, panel by panel, the effect of a cloud passing overhead, as well as the shading from a single tree as the sun moves across the sky. Rather than one or more strings having total output cut to the lowest common denominator panel output, each panel responds separately. What other factors may be important in this decision?

 

[peakbagger]

String inverters are lower cost overall and they have the SMAs have the SPS feature. If the array is distance from the house, the DC voltage is higher which means smaller wire gauge then microinverters. Electronics like cool dry conditions, some installers install them outdoors in hot areas and they are going to fail more often then one is cool basement.

Historically inverters have a 10 year life, they can get damaged from external surges. If you plan to be in the house for 20 years it may be worth it since the government is paying for 30% of the warranty. The opposing argument is the price of inverters is always dropping and new features appear so in 10 years if the inverter fails a new inverter may be better and less money than the $300 you paid for now. Your call

 

[7acres]

String inverters are lower cost overall and they have the SMAs have the SPS feature. If the array is distance from the house, the DC voltage is higher which means smaller wire gauge then microinverters. Electronics like cool dry conditions, some installers install them outdoors in hot areas and they are going to fail more often then one is cool basement.

Historically inverters have a 10 year life, they can get damaged from external surges. If you plan to be in the house for 20 years it may be worth it since the government is paying for 30% of the warranty. The opposing argument is the price of inverters is always dropping and new features appear so in 10 years if the inverter fails a new inverter may be better and less money than the $300 you paid for now. Your call

Good points about warrantying the inverters. The installer is planning on locating them underneath the panels so they are in the shade. Yeah, the panels will be about 120' from the meter.

There is a big oak overhead now. If we go through with this I will drop it and clear the scrubby stuff in the area. There should be very minimal shading from trees after that.

Speaking of inverters I started reading up on the SMA Sunny Boy Sunny Boy 5000TL-US and saw that it has been discontinued by some online sellers while still for sale at other places. After more research it appears that SMA has recently come out with an updated version of the inverter, the Sunny Boy 5.0-US. Should I insist on the newer model? Or are both of these models current and just serve different purposes?

 

[7acres]

Confirmed the 5.0-US is the new model. The installer has agreed to install the new model for us.

 

[peakbagger]

Glad you answered your own question. Saves me pulling out the spec sheets and comparing them Generally newer model inverters usually cost less once the old units are closed out and have more features. I expect the new versions deal better with the new RSD requirements (that you get to ignore since you went ground mount).

So when are you pulling the trigger?

 

[7acres]

So when are you pulling the trigger?

As soon as possible! We're definitely doing this. My wife and I have run the numbers and this makes amazing financial sense. We just have to complete the refinancing of the home loan (which we were doing already for unrelated reasons). We just have to up the amount of cash we're getting out of it to do the solar project.

 

[peakbagger]

If you are doing the project and you understand your taxes, you can get creative with your W-2 and claim extra exemptions to reduce your paycheck withholding to account for the large tax credit you will be getting in 2016 as long as you are guaranteed by the installer that it will be up and running by 12/31/16. I think most folks will just leave the exemptions as is and get big deductible but I prefer to have the cash in hand rather lent to the government. If for some odd reason the system doesn't get installed and approved then you will owe the government more and may get a penalty for under withholding.

Some folks think this is illegal but it is not, here is a discussion.

http://articles.latimes.com/2013/mar/31/business/la-fi-lew-20130331

 

[7acres]

So, here's an update. Longstreet mentioned upsizing. I asked about that and they said they can upsize the combiner to accommodate this for only roughly a couple hundred dollars more.

Somewhat unrelated to the upsizing I inquired about the SPS backup power option and having the outlets run to the back of the house instead of having to run extension cords down to the inverters located under the panels in the event we want to use it. They came back and said they could simply bury rigid conduit up to the house (buried DC up to the house) and site the inverters on the back of the house. This will give us max 4,000 watts of solar powered backup power in the event the grid is down.

Finally they will size the conduit such that there is room to pull another wire if we expand the array at a later date.

I like the way this is coming together.

 

[DBoon]

They offer a $600 warranty on the inverters. They said the chances an inverter will fail in the first, I think they said 10, years is very high. I'll have to get the specifics on that offer again. Is an inverter warranty a good idea?

I would not buy an extended warranty on the inverter - if the inverter lasts for the first few weeks, it will probably run 10-15 years if properly surge protected and kept in an appropriate environment. The nature of the power electronics is that they will fail early or last a long, long time.