# Solar panels for the home...



## Warm_in_NH (Mar 21, 2014)

Met with the solar guy last night to see if they're an option on our house. 

Long story short, says we need about 8 KW of electricity, thus 8 panels, at a cost of about $1000 a panel installed. 25 year warranty, $1000 state (CT) rebate, $2100 federal tax credit, total cost out of pocket $4900 +/-. 

Overall, if no one is bs'ing anyone, it would be about a 7 year pay back. We would still have the $17/mo. connection fee from the power company, but he claims that's it. 

The real killer is that despite the fact that the house faces due south and gets crazy sun, for the panels to run at a minimum of 80% efficiency (thus qualifying for the tax credits and what not) 3 giant old beautiful historic maples would need to come down, not really an option as far as we're concerned right now.

So, I'm asking if anyone's made the switch to solar, and what your experience has been with it? Are the claims of zero electric bills reality or a sales pitch? 25 year warranty, but what's the real reliability of the product? Any other info anyone can offer up would be helpful as well. 

Thanks.


----------



## peakbagger (Mar 21, 2014)

Something doesn't line up but it just may be how you are describing it. It may be you are getting confused on KW vs KWH. An 8 KW system is 8000 watts of panels, There are no commercially available panels rated for 1 KW each so I expect that he is proposing installing some combination of panels that produces 8 KWH per day. The difference is that a 1Kilowatt ((1KW) set of panels lined up in perfect sun conditions (called STC)are  lined exactly perpendicular to the sun for one hour, it produces 1Kilowatt hour(1KWH). The sun moves all day and the panels don't plus it rains on occasion and the length of daylight varies, so the designer of the array uses a program like PVWatts and your location to estimate how many watts of panel you need to generate 8 KWH. 8 KWH per day is actually quite a small system. My 4800 KW of panels put out 28KWH on a recent sunny day, of course The day before it put out about 2 KWH. Thus the first question is what is the rating of each panel?. Current grid tied panels range from 245 to 335 watts per panel. The going rate for a installed solar system is around $3 to $5 per installed watt of panel rating. Then subtract the CT incentive and federal tax credit. I would be quite surprised if the proposed system is anywhere near the size you need to offset your load on a day to day basis but that's what PV watts will tell you as it calculates the output over the course of the year.

A seven year payback is about the going rate for a commercially installed system. The 25 year warranty is a bit of an issue, the industry is still growing and few companies will be around in 25 years. Enphase microinverters is about the only company that offers 25 years and they haven't made a profit since they started, I am not sure how bankable a 25 year warrantee is from them. Same with solar panels, few companies seem to be it in for the long haul. Central inverter warrantees at best are 10 years. The panels themselves unless they have manufacturing defects should last 25 years or more although they will lose some capacity as they age.

Shading of the panels is a major no/no and in order to comply with rebates the installer has to check for shading to the south and that usually means no trees to the SE,S & SW of the panels. Trees grow and you need to make sure that someone doesn't build a large structure or grow large trees to block your sun. Check your roof pitch, if the roof holds snow, you may have issues with snow on the panels in winter.

One general note is that a standard grid tied solar system does not work when the power goes out. One firm SMA offers an emergency power option for larger systems but it has a slightly higher initial cost. You can get a system with battery backup but plan on several thousand dollars more up front plus occasional expensive battery change outs.

I haven't had a power bill for a couple of years and haven't had any significant issues except the power company zapped one of my inverters. It was on warrantee and I got a replacement quickly.I would check your net metering options with your utility, some systems only let you carry a credit for 12 months and then they reset while others like NH allow me to run a ongoing surplus.The fed rebate goes away in 2016 so you have some time but not forever to get a system installed..Check to see if you can get SRECs which is an ongoing incentive that depends on how much power you generate.


----------



## jebatty (Mar 22, 2014)

Check out my thread. I get a chuckle from those who demand short term payback for an "infrastructure" home improvement. Do you buy a house that will payback in 7 years? And a house is far more an expense than an asset. Based on alternative current, very safe, tax free, inflation hedged investments, IMO my system is an absolute winner. https://www.hearth.com/talk/threads/solar-electric-6-5-kw-system.116031/

The link also discusses shading, and I fully agree that shading can be a serious issue. I regard my shading as as inconsequential.


----------



## mustash29 (Mar 22, 2014)

My environmental manager at my work (trash to energy plant) has the following:

Grid tie solar with nety metering but no battery backup.  He has the minimum $17 / mo POCO charge to be grid connected, but other than that he essentially has no electric costs.  some months he has a small bill, some moths a small credit.  I'm not sure how big his system is, but for he & wifey it does as above.  If the 2 kids are home from college / military the electric use is higher.

He has oil / HW baseboard but rarely uses it for heat, but it is hot 24/7 due to the tankless DHW coil.  I have pointed him toward electric DHW or HPWH DHW (GeoSpring & Geyser).

He heats with a ducted pellet hot air furnace.  There is no A/C.

He did mention something rather strange about his electric rates.  There is a certian cut off date associated with peak demand pricing and a subsequent lock in at lower rates.  Basically he turns off the hot tub in the summer.  This drops his summer peak demands and puts him in a lower $ / KW bracket for the winter months.  In winter he can run the tub on the cheap.  It allmost sounds a55 backwards.


----------



## Warm_in_NH (Mar 22, 2014)

Peakbagger. Thanks for the thorough explanation. Yes, the electric bill states that the average usage of the home is "7kWh" this is why the "salesman" said we would get full coverage from a system of 8 panels each producing 1 kWh, measuring 40" by 66" per a panel. It was truly confusing to say the least. As a home improvement contractor myself, having to do in home estimates and present product specs to my customers, I was surprised at the vagueness of his answers.

The prices, the vague info, the "simplicity" of the set-up, the "lease option" etc, seemed to have a lot of holes in the explanations.  This was all through Trinity Solar. I was really hoping to get a better education from the meeting, I thought I learned a bit until I read more on here that showed me how inaccurate his info was.

Granted it was a bit of a brief explanation due to the fact that I told him removing the trees probably wasn't an option. However, when we called the company a few weeks ago, they take a look on google earth to confirm you house location, what roof is best, and that phone call ended with, yes, you can have solar, no install costs, no modifications to the property, we'll send the consultant over to hammer out the details. This was my fiance that made the call, relayed the info to me, I said something seems "off" I think I'll be there for the meeting. Glad I was, cause I would've though she took down bad notes or didn't listen.

I found the thread that jebatty linked to last night and read it over, the holes in the salesmans story started to show through.

Jebatty: "I" didn't say that I expected it to pay back in 7 years, the salesman from Trinity Solar did, thus my skeptic attitude and my post on here to get additional input. IF that was the case, it would've made dropping the said trees more of an option (firewood!) to live with no electric bill for 18 years under the solar warranty. Resulting in a net savings of nearly $14,000 before the warranty ran out and several cord of wood for the stove. 

Thanks for the link to your thread, interesting, thorough, informative, answers most of the questions I was hoping to when I started this thread. Can't delete it now that it's started, but between Peakbaggers input and your thread, I'm all set.

Once again in life we learn that if it seems to good to be true, it probably is. 

Thanks!


----------



## Warm_in_NH (Mar 22, 2014)

So we just walked the dog around the block and I took note of one of the neighbors array. Appears to be 3 times the size of what they were saying we would need, similar size home.  
Shady solar sales. ..


----------



## DougA (Mar 22, 2014)

If the trees are providing a lot of shade for the house in the summer, you will increase your need for a/c in the summer - a lot.  In Nov., Dec, Jan. you will get very little power from your panels and there is nothing you can do to change that. Solar can make a great addition to your energy plan but you have to look at everything.

BTW, I've been doing a ton of research on Solar but not posting much. $8K for an 8Kw system installed seems too cheap.


----------



## begreen (Mar 22, 2014)

Yes, that price waved a flag to me too. Locally our installed price is around $4-6/installed watt depending on the setup. That is with WA state made panels which are more expensive, but earn a hefty energy credit.


----------



## DBoon (Mar 22, 2014)

I think there is some easily corrected confusion here. If your demand averages 7 kWh/day throughout the year, and you have a (reasonable) average of 4 hours of sun/day, then a (fairly normal) 250W panel would produce 1 kWh (4hours x 250 Watts = 1000 Wh, or 1 kWh) per day. 

Every home is different on usage.  Your neighbor could have electric hot water, electric range, electric stove, 3 kids, etc.  His usage might be three times yours, thus three times the number of panels. 

As far as payback goes, if you are producing 8 kWh/day for 365 days/year, that is 2,920 kWh/year.  To pay back a $4900 (net) system in 7 years, your electricity would have to cost 24 cents/kWh (2920 kWh/year * 7 years = 20,440 kWh, $4900/20,440 kWh = 0.239 $/kWh).  I don't know what retail electric rates are in CT now or during the summer, but an average of 20 cents (or more) per kWh wouldn't surprise me one bit. 

As far as reliability goes, while your solar panels (if they are not cheap Chinese made junk - my opinion) may last 25 year, the inverter most certainly will not.  Expect to have to replace this every 10 years or so.  Anything beyond that is a bonus.

I'm with jebatty on payback.  Do this because you want to invest in power price certainty, or because you think it is the right thing to do. I wouldn't make the call based on whether it was 7, 10, 12, etc. years of payback.  It will most certainly be <15 year payback, for what it is worth.


----------



## Where2 (Mar 23, 2014)

I can tell you right now, you're not going to get 1kWh out of each of those 8 panels every day, especially not in winter. You might get it 5 months of the year, if you're lucky and have 0 shading problems. It would be worth your time to go talk to your neighbor with the panels. See if you can get specs, and real world data.

My experience is with my own 20 panel, 4.4kW(DC) system in the "Sunshine State" at roughly 26.8°N. My sunshine cuts through a lot less atmosphere than it does to reach central NH.

Here's where I go to mine data for my friends when they ask me what solar would do on their home:

Look around the map here:
https://enlighten.enphaseenergy.com/public_systems
After you zoom in, click on one of the little orange E cartoon bubbles. Some of them will bring up systems on the right side of the screen with links that can be followed to review the actual system data.

You may wish to look at these systems for reasonable example sake:
https://enlighten.enphaseenergy.com/pv/public_systems/Dh5Z20778/grid/months
https://enlighten.enphaseenergy.com/pv/public_systems/xRcD16574/grid/months

Given that both of these example systems were installed in 2011, we can make some basic assumptions: these are not current cutting edge systems, a modern panel + inverter might generate ~5-20% more energy per day than these do. (However, these example systems may actually have been SolarWorld 240 mono panels with Enphase M215 inverters which would put out very close to what a modern 250W panel would). Take any system's output data (in kWh), divide it by the number of panels listed for the system (or # micro-inverters listed), and multiply the result by 8 for your proposed system. For broad brush strokes, look at the monthly data. Compare that monthly kWh # you computed to some of your energy bills over the last few years.

From what I see, 8 panels might cut it in the summer months, but not the cold half of the NH year.

One thing to note about incentives: _the federal incentive is a "Credit" against your wage based tax liabilities. It is possible that you may have to roll a portion of the credit forward into the following tax year, so waiting to 2016 might not be the best plan for all wage earners. Consult your tax advisor to determine what is best for your situation._


----------



## DBoon (Mar 23, 2014)

Where2 said:


> you're not going to get 1kWh out of each of those 8 panels every day


I was discussing "average" not guarantee or typical.  If you have net metering, average is what counts.  Of course, the daylight is shorter in the winter, so there will be less production.

This link http://www.nrel.gov/gis/images/eere_pv/national_photovoltaic_2012-01.jpg indicates average sun hours/day for photovoltaic systems - it shows between 4 to 4.5 for NH or CT.  If the panels are 250W, and the sun shines 4 hours a day, that is 1000W, less any inverter and other system efficiencies (realistically, this would mean about a .88 multiplier or so in the Northeast, leaving ~880 Watts. 

The OPs original question was "is the installer feeding me a line of bull*&^%?" and I think the answer in terms of system sizing (based on his 7 kWh/day usage) is "no".


----------



## Warm_in_NH (Mar 26, 2014)

Thanks for all the info. Like I said, it was just a preliminary meeting with the rep from the company and it really seemed too inexpensive and promised way too much.  Said and done, I do think the salesman was omitting certain facts and numbers, he couldn't answer many of the harder questions, not sure if it was intentional or not, but it sure wasn't a complete and thorough description of how the whole set-up would work.
There's a LOT more to it than he let on, this thread as well as the other that was linked to near the top really filled me in on a lot of the costs, needs, and fine details. 
While solar is probably a good way to go for many, when we need to cut down a combined growth of over 600 years worth of healthy trees, I just can't bring myself to consider it an option at this time. 
Thanks again for all your input, number crunching, and explanations. Very helpful.


----------



## peakbagger (Mar 26, 2014)

Solar is definitely a salesman dream. To the average homeowner its difficult to understand and with the myriads of incentives that vary, its easy to obfuscate the truth.


----------



## Dave A. (Mar 26, 2014)

Just following the numbers to get an idea of costs and if I were to do it I'd want to be able to at least heat (with a heat pump) and cool with it.  For me that would take more like 30 or 40 kwh/day (or maybe even more).  That's a lot of panels.


----------



## DBoon (Mar 26, 2014)

Warm_in_NH said:


> While solar is probably a good way to go for many, when we need to cut down a combined growth of over 600 years worth of healthy trees, I just can't bring myself to consider it an option at this time.


Kudos to you - those trees are doing some good just where they are, and will for a long time to come.


----------



## jebatty (Mar 27, 2014)

This may read to be a little absurd for a guy like me heavy into sustainable forestry management, but I too could not cut down trees around our house to allow a roof mount solar system. The solution was buying some open land from a neighbor and installing a ground mount system about 300 feet from the house with underground wiring, including going under the public road. The cost of the land, of course, is not included in my system cost. System cost before any incentives was around $4.75/watt and around $3.40/watt after the federal tax credit. I am very happy with the ground mount which is very easy to clear of snow. In our area panels could remain snow covered for a 1-2 months, and I would not look forward to climbing up on a snow covered roof to clear panels of snow. Winter production (Nov-Jan) is only about 30-40% of summer production, but every watt counts when you have a solar system.

March predicted daily average for me is 27kwh/day and I am averaging 33 kwh/day. Dec daily average was about 9 kwh vs 13.5 kwh predicted. July average is predicted at 39 kwh/day.


----------



## AK13 (Apr 4, 2014)

OP, this thread has gotten me a interested in solar. Do you recommend any of the installers that you've talked to? Are you in NH or CT (can't tell from your posts)?

Does anyone have a solar PV installer they can recommend for South Eastern, NH? I see Revision Energy out of Exeter (and Maine).


----------



## peakbagger (Apr 4, 2014)

Revision travels all over NH and into Mass. I would definitely have them on your list. They have done several systems up in North country (Randolph and Milan NH)

They are big enough to buy panels and inverters in bulk. I think they do mostly microinverter installs which means that they have a standard kit that they carry that covers 95% of the install parts. Most of the time they can be in and out in a day.

Biggest obstacles for most folks is shading, roof orientation and the age of their roof (don't install a new solar system on an old roof as it will last far longer than the roof).


----------



## AK13 (Apr 4, 2014)

peakbagger said:


> Biggest obstacles for most folks is shading, roof orientation and the age of their roof (don't install a new solar system on an old roof as it will last far longer than the roof).



I think I am good on the shading. My roof points southwest. And the roof is only 2 years old (unfortunately its asphalt and not a fancy metal one) and they stripped it down to the sheathing so there is only one layer of shingles. So maybe I'm in business! 

I'll follow up with a phone call to Revision.


----------



## Vic99 (Apr 5, 2014)

I got three quotes and ultimately selected ReVision to do my install.  I went live Oct 2012.  They were genuinely interested in doing a good job.  My house is almost 100 years old, but my asphalt roof was only 3 months old.  They got it done in 4.5 days (they predicted 3), but the crew leader was a real perfectionist to make sure that all the panels lined up such to make a flat plane on an uneven roof.  I also bought a bigger system than I needed with the idea of future growth in mind.  Sure enough, I bought a Chevy volt in Oct of 2013.  We'll see if I sized it right to break even next fall.

Good luck.


----------



## begreen (Apr 5, 2014)

Congrats! Keep us posted. 

PS: How did the Volt do through the winter?


----------



## Vic99 (Apr 5, 2014)

The Volt was fine . . . once the need to obsessively hypermile wears off.  Used engine assist for heat a lot because it was either cold or I had the family in it.  I can deal with just the heated seat when temps are in the 30s, but below that for anything more than a short trip and I fold.  Low life time mpg was 125.  Back up to 140 now and expect to peak around 180-200 at some point.

We got a higher amount of snow than usual here in New England.  People were starting to sour on the snow in February.  Come on . . . its New England.  Using L gear makes the car much better in the snow than I had expected, so much so that I hardly used my truck.  It really is a well thought out vehicle.


----------



## AK13 (Apr 7, 2014)

Well I have ReVision coming out but not until a week from Wednesday. I can't wait. 

Meanwhile I'm trying to figure out what will fit on the roof. Its a 26' long by 15' pitched roof. I'm bummed because I wanted to go with 5+ kw and it looks like standard 250 panels run at around 65"x40" or so. So I'll only be able to get 16-18 on the roof based on my calculations. It looks like either a grid of 4x4 running the long way. Or a grid of 2x7 with a row of 1x4 at the bottom would work. Oh well 4.5 kw will be okay too if that is all I can fit. But I was really hoping for 3 rows of 8 and 24 panels total for a nice 6 kw array. Doesn't look like that is going to happen.


----------



## Where2 (Apr 7, 2014)

I've been in that predicament. There's only 4.4kW on my second floor roof, because that was all that would fit...

4.4kW is better than 0kW.


----------



## Vic99 (Apr 7, 2014)

Steve from ReVision assessed my set up. He had a lot of good ideas and was open to reasonable input.  At the time they sold Canadian Solar panels (made in China), Suniva (made in USA - what I got) and Sunpower ( Philippines, I think.  Supposedly the gold standard, but also very expensive).  I got a 6.3 kW system, but realistically it runs a bit less than that.

Sunpower might get you more energy per square ft, but you'll pay more for them.

If you have any shading issues at all, get microinverters instead of a single or two string inverters.  With a string, if one panel gets shade, all the others on that string only produce what the shaded panel gets.  Plus microinverters allow you to detect if there is an issue with one panel instead of having to guess which on the string it is.  This actually happened to me.  A squirrel built a nest under a panel and chomped through a wire.  Revision came back and installed a rodent proof mesh between panels and roof.

If you get microinverters, ask if and where they clip.  My enphase have a max of 225 W.  Might have higher rates ones now.  Even though my panels are rated for 255W, I can never get that.  Realistically, though, they very rarely get to 225.  Often I hit between 210-220 when angle of sun is right.  Max out in Jan or Feb if we have a 10 F day as the panels become more efficient with colder temps.  That's probably why April is my best month.  Balance of being somewhat cool and longer days.

Good luck.


----------



## peakbagger (Apr 8, 2014)

The new fire code is really screwing up panel installs. A strip along the sides and then along the ridge line can eat up potential panel space.

Part of the issue with clipping is the panel orientation. I have two adjustable arrays and one fixed roof mount. The adjustable arrays do routine try to overproduce in winter as they are tilted optimally and get a lot of extra sun from snow reflection plus the back of the panels are exposed so they are quite cold. I had a prior setup with 1100 watts of Siemens panels on a 2K inverter. I saw a sustained 1250 watts off the array one cold clear winter day for about an hour. The same inverter now has 2100 watts of Evergreens and it does clip out at 2050 which is the inverters max output. My roof mount angle  is definitely not optimal for winter. When its not covered with snow I haven't seen it putting out anymore than the panel ratings. It has an oversized inverter.

 Its tempting to swap inverters but unfortunately they are built to different NEC code revisions so if I do swap, I end up with one system that is no longer built to code. One definite disadvantage to selling SRECs (owner has to certify that the system is built and maintained to code).


----------



## jebatty (Apr 19, 2014)

My panel/inverter matching is pretty good. Panels are rated at 6900 watts total (26x265) and inverters are rated continuous at 6500 watts total, but I regularly will see total output in the 6700+ watt range before clipping becomes apparent.


----------



## WoodNotOil (Jun 19, 2014)

Vic99 said:


> If you get microinverters, ask if and where they clip. My enphase have a max of 225 W. Might have higher rates ones now. Even though my panels are rated for 255W, I can never get that.



The Enphase M250 is rated for peak 250w and continuous 240w output but averages $50 more than the M215 which is rated 215w continuous output.  Reportedly the M215 will clip at around 225w.  I notice that many installers and kits pair the M215 with panels ranging between 200-255w.  I guess you have to do a cost benefit to what you lose when it clips on the occasions you manage to reach that point vs the added cost of the M250...


----------



## Jags (Jun 19, 2014)

What is the fail point on the inverters?  It seems as though it shouldn't be difficult to build these with a life expectancy greater than 10 years.  They are solid state, correct??


----------



## begreen (Jun 19, 2014)

Heat, transient spikes, back feed from generators are some of the issues I've read about. The early Enphase inverters seem to have issues with caps drying out in the heat behind panels. Not sure if that is now history or not.


----------



## jebatty (Jun 19, 2014)

There is some logic supporting inverters with a continuous rating somewhat less than panel rating. My highest peak production so far has been in March and April, cold and clear. Since then clear skies with warmer temps and higher humidity have brought peak production down. Then add in pollen and dust on the panels, and that too brings peak production down. So saving a bit of money on less expensive inverters with a lower rating is a real savings. And don't forget to wash the panels once in awhile if possible to get the dust off.


----------



## peakbagger (Jun 19, 2014)

The past failure prone part of an inverter was the capacitors as most inverters use them and capacitors seem to have a finite life made worse by heat.  I lost an inverter due to a power company spike. My old inverter rode through it but the Fronius got hit and cooked a chip. I had delta transient surge suppressors on the panel and the inverter and they didn't pop but after reading several articles, the deltas don't clamp anywhere near low enough  to protect much. I installed a couple of midnight solar suppressors which  have a far lower clamp voltage. I hope no to test them.


----------



## Jags (Jun 19, 2014)

jebatty said:


> There is some logic supporting inverters with a continuous rating somewhat less than panel rating.



So there is a significant cost difference between a 215 watt inv. when compared to 250w?  (admittedly I know nothing about pricing for the supporting items of a PV system)


----------



## Where2 (Jun 19, 2014)

Jags said:


> So there is a significant cost difference between a 215 watt inv. when compared to 250w?  (admittedly I know nothing about pricing for the supporting items of a PV system)


Street prices from a reputable dealer I have used in the past:
M215=~USD$134.50 (without the integrated ground feature)
M215=~USD$139 (with new integrated ground feature)
M250=~USD$163.00

Over the weekend, I thought: I haven't washed my PV array since I put it on the roof a year ago, I should wash a couple panels and see if there is a measurable difference in output. Much to my surprise, I find the rain in South Florida does a fine job of keeping the remarkably panels clean. After 5 days of collection, I see no improvement in comparison to the adjacent panels versus the week before. (the tree in the distance in my avatar is a live oak tree).


----------



## begreen (Jun 19, 2014)

I have to wash heavy pollen accumulation off the panels every spring. And off our cars too. Leave it on and it feeds algae and turns to green slime.


----------



## Jags (Jun 20, 2014)

Where2 said:


> Street prices from a reputable dealer I have used in the past:
> M215=~USD$134.50 (without the integrated ground feature)
> M215=~USD$139 (with new integrated ground feature)
> M250=~USD$163.00




Hmmm... so 30 bucks.  I find this curious.  In the world of amplifiers I always used the 80% rule for power.  If you need more than that, you step up.  If I was banging off of the clamping circuit, that was meant as a warning to me.  Does this not hold true in the world of PV?  I just find it interesting that a person would intentionally run with the smallest inverter they can get away with.  Maybe efficiency?  It just goes against my nature to run something at 100% to the point of clamping the output.  Is this common for PV?  I must be missing something.


----------



## peakbagger (Jun 20, 2014)

Not sure on Enphases but some long term solar vets had told me that the concept of intentionally clipping an inverter in order to save a buck instead of buying the next bigger unit is not a good policy in the long run. Knock on wood I have fairly old Advanced Energy Inverter that is lightly loaded that keeps humming along after many years. Most of these units were maxed with more connected wattage than the rating so they clipped on occasion and most of them are no longer working. Maybe I am just lucky mine still works but I expect it has to do with running it at under its input rating . Of course mine is also in a nice cool basement not in the hot sun or far worse like an microinverter, bolted under a panel above a hot roof.

The vets I knew had been PV from the early days on high reliability systems in remote areas so they tended to be very conservative as a service call to Greenland was a major effort. Most installers now are in it to make a buck and go away so I expect they figure what is the lowest cost and figure the warrantee will cover it.

I don't know what I will do when that inverter dies, the array is small and the string voltage it too low for most grid tie inverters.


----------



## WoodNotOil (Jun 20, 2014)

peakbagger said:


> Not sure on Enphases but some long term solar vets had told me that the concept of intentionally clipping an inverter in order to save a buck instead of buying the next bigger unit is not a good policy in the long run.



If you are competing on price for sales then this could definitely be the case.  In a scenerio where you have say 20x250w panels and your microinverters clip at 225w then you are losing 500w of production if all panels were producing at max rate.  That seems significant, but I wonder what percentage of the time you can really be producing at that rate for it to matter.  Is that worth the 20x$30=$600 to go up a size in inverters?  To you and me over the lifetime of the panels, probably yes.  To the company who's solar package looks more expensive than the next guys, probably not.  Maybe they should price the packages with the lower inverters and then talk you up once you commit to buy.


----------



## jebatty (Jun 21, 2014)

My comment 





> There is some logic supporting inverters with a continuous rating somewhat less than panel rating.


 was not suggesting that material under-sizing because of price control the decision on microinverter purchase, but was suggesting there may not be a benefit in over-sizing the inverters. My panels are rated at 265 watt and the highest output I have seen is 269 watts. My inverters are rated at nominal 250 watts, 265 watts maximum, usable with panels up to 300 watts. So far this summer maximum panel output has been about 240 watts, while maximum power output during the late winter (Mar-Apr) did hit 269 watts but more normal maximum was 265-268 watts, with periods (up to about 2 hours) above 260 watts on clear days. At 269 watts output that continued for more than a brief period of time, the inverters clipped back to about 268 watts. I never noticed any clipping at output in the 265-268 watt range.  

So, should I have bought inverters with a higher rating (nominal 300 watt for Aurora)? I doubt it. I think that the inverters are just about exactly sized for the panels. Will operating the inverters towards the higher range of their rating result in failure at an earlier date? I don't know, but I think that the passage of time is more likely to result in failure than operating the inverter in the higher range of its rating. Absent real data, a person can only speculate.


----------



## Vic99 (Jun 21, 2014)

WoodNotOil said:


> If you are competing on price for sales then this could definitely be the case.  In a scenerio where you have say 20x250w panels and your microinverters clip at 225w then you are losing 500w of production if all panels were producing at max rate.  That seems significant, but I wonder what percentage of the time you can really be producing at that rate for it to matter.  Is that worth the 20x$30=$600 to go up a size in inverters?  To you and me over the lifetime of the panels, probably yes.  To the company who's solar package looks more expensive than the next guys, probably not.  Maybe they should price the packages with the lower inverters and then talk you up once you commit to buy.



My M215s clip at 225 for 255W panels.  At 25 panels, you'd think I would be losing over 600W.  However, I only seem to hit 225 1) in the winter below freezing and for less than a couple of hours and 2) once in a while during a cooler day during the rest of the year.  My panels face south (185 degrees) and 10 slope 28 degrees and 15 slope 56 degrees.


----------

