To pull the trigger or wait, new solar PV

New England SteamWorks

I am no expert on solar either, but my understanding is that a huge component of making this stuff affordable/viable is via government subsidy.

And what Government gives, Government can take away. Any time they want.

Years ago we bought our historic house and at the time there was a very nice 10-year historic tax credit if we ponied up big bucks upfront. Which we did.

We got 3 years of tax credits and then they ended the program. What about the other 7 years we asked?! A deal's a deal!

-Tough luck they said!

GW

Bummer, what government agency, I’m guessing Mass? I’ve never heard of a tax incentive getting pulled back, but I’m kinda clueless with most tax ins and outs

hot_rod

We found consumers will buy when a few things line up. High fuel cost, high public awareness driven by the administration in office, and incentive packages. When any of the three starts to wane, interest drops.

For a HO when incentives cover around 50% of installed cost they are comfortable with the ROI or payback numbers and tend to sign on.

With state and local incentives, often times a pool of money is allocated, and when it runs out the program ends or waits for lawmakers to refund it.

So with that DSIRE web sight it's wise to check every few months, they have been keeping it updated, first come first served with many of the programs.

The federal 30% did get abused in the beginning, people would try and get 30% on an entire radiant/ DHW heating system just by putting a few collectors on the roof.

If you don't pay Federal taxes for whatever reason, like some high ranking govt officials, there was a way to actually get a check for the amount.

Best to have a CPA look over any complicated rebate programs to stay out of trouble.

D107

@GW Here in NY the subsidy is a one-shot deal, all up front. I wouldn't expect more than that. Seems to cover 50% to 65% of costs. I'm sort of in the same position you are. Our municipality has entered into an agreement with a solar contractor--after vetting about three companies. We'll have until June to sign a contract to get their special price for the rooftop micro-inverters. I have a meeting with a rep Monday and will let you know what I find. Regardless of the current efficiency rates, I will be looking closely at:
1. Maintenance issues and costs, cleaning, warranty.
2. Actual yield in our climate, given our roof pitch, inability to adjust panel angle by season, panel type.
3. ROI; I'll be checking out their references to see about the yield, any water leakage, whether they use roofers for sealing or just their people. (I have just installed closed-cell foam in the rafters under the roof, so if there was a leak, it might be a long time before I would know about it.)
4. Ascertaining whether panel performance decreases when temps are over 80deg. F as I've heard or if heat from panels adds to summer cooling load--even though some claim panels block the sun and thereby reduce cooling load.
5. Can system be used during power outage--many areas do not allow this--with microverters?––to prevent electrocution of workers repairing the power lines.
6. Rate of efficiency degrade over time and overall panel and roof longevity. (Our white birch energy star-rated reflective shingle roof is now 5.5 years old, has lifetime overall manufacturer's warranty.)
7. Whether panels attract lightning.
8. Monitoring system

These companies claim net savings of $27K over 20 years, with ROI of 4 years, and 3%+ property value increase. They claim only 13% performance reduction over 25 years. This is the Sun Power Equinox system using Sunpower Maxeon Solar Cells.

I think you're asking the right questions and getting answers from some really smart and experienced people. Skepticism is required these days. (I recall when all the ESCOs made crazy claims of $$ savings if we let them buy our electricity for us some years ago. Alot of people lost money with that.) I won't add solar just because it feels good to go solar.

To your question of whether to go now or wait, it may depend on how quickly efficiency is liable to rise to that supposed max of 46%. Bottom line is to use very conservative figures for yield and see if the numbers add up for a twenty year period. Without the government subsidy, I wouldn't even be considering it.

BobC

there are good Chinese inverters and crap Chinese nverters, if you choose poorly the warranty is not worth the paper it's printed on.

Bob

Leonard

38-46% efficiencies. ..........

That's VERY high. Could you please post a link to that I'ld like to read it. Last I read R&D tests were closer to 23 maybe 26 % at best.

It didn't say the % but lot of stuff is being published about R&D results of dye based solar cells ( engineering magazine = Vaccum Technology and Coatings) . Multi layer ,each layer absorbing different wavelength of light and passing the rest to next layer for higher overall % . But haven't heard of it in production yet, just experimental right now.

Thing is cutting edge state of the art is $$$$$$$. Mars rover solar cell was ~ 1 inch square, made ~1 watt ,and cost several thousand dollars for that 1 watt. Think it was 18%, HIGH at the time.

Gordy

Just search NASA web site. Yes NASA technology finds its way into mainstream eventually, at a lower cost, and after the tax payers are tapped for R&D.

Do a little search on WiKipedia also.

I also find it interesting as panel temperatures climb efficiency goes down. So at what panel temperature are the advertised efficiencies?

Leonard

Likely cool temps, for sales promo reasons.

Guessing lower voltage at warm temp is electron/hole recombining in the solar semiconductor. Or could be IR loss, even copper increases resistance by ~ 0.4%/deg C., so increasing temp from 60 deg F to 120 increases collector resistance by ~ 13%. Guess which one depends on if voltage reduction with temp occurs at no-load or under load.

Read in electricians magazine EC&M that the basic panel makes higher voltage in cold temps. Artical Had to do with electrical NEC code limiting max voltage a string of panels can make, so it puts a limit on how many panels you can connect in electrical series. Think voltage limit is ~ 600 V. (this is more for if you use one inverter for all the panels)

WOW 46% impressive !!!! Sounds like cutting edge R&D lab prototypes, not production panels yet. Well, ok chart is labeled best research (solar) cells
https://upload.wikimedia.org/wikipedia/commons/0/01/PVeff(rev171030).jpg

GW

The quote has LG panels, inverter. I have the brochure somewhere

D107

So hoping this info will be useful to Leonard: I've been getting info on the fastening method into our asphalt roof. See photos. They seem to use flashing, mastic , butyl mastic tape, etc. My concern is they say they often fasten through shingles into decking not rafters. With older houses, decking is often tongue in groove 1x6s. So with many decking areas not in great shape and the groove area being weaker if fastened into--36 holes!-- I'd prefer fastening to rafters. If a house has closed cell foam under decking, any leak would be hard to detect and the roof would suffer. Company claims they've had no issues with leaks. Been in business 15 years, good rep. and references. They first send out structural engineer to ensure roof is sound and verify particular fastening method.

Leonard

The tucking under the shingle method sounds good......as long as have enough tuck, and slope of roof is larger enough to use shingles. Check on if near drip edge about ice dam issues. Here on sloped roofs under the shingels they lay down a roll of sticky butathan ? rubber for first 3-6 ft up from drip edge to stop ice dams backing up water over TOP edge of shingle.

Screwing into decking .......agree that might be a failure point with winds. Or if happen to screw near edge of board, or into a wood knot.

I don't really like screwing into rafters since I've seen people crack the rafter that way. Guess they drilled a SMALL pilot hole then cranked in a large dia lag bolt....CRACK. Especially a problem with old dry lumber

I suppose the method I like best would be to nail in a wide board between the rafters then screw into that. Maybe a board 4 inch wide by height of rafter board....... Might be over designed, but I design military equipment. It all depends on the structural loads panel will apply to the wood. Wind could be the largest load.

I'm not a civil engineer but I've had to calculate wood bending stresses when tenets add HVAC equipment to the roof. I see lot of carpenters doing stuff that's flat out wrong.

Problem is electricians and plumbers have to pass state tests proving they are competent to get licensed. Any kid can pick up a hammer and call himself a professional carpenter, there are no tests for competency. This causes all kinds of legal problems when incompetent carpenters do shoddy work. Think carpenter licenses are only to make sure they pay state taxes on the job.

Other thing is make sure you make THEM responsible for meeting building code. Some fly by night "carpenters" write into your contract that YOU, not they, are responsible for meeting code and getting permits. This basically means they can do ANY GARBAGE work , get paid, and walk away. Seen it happen.

Fred

I'm not a fan of solar panels mounted on the roof of a primary structure at all. Too many possibilities for hidden damage, over the life of those panels. I think they should be mounted in some free standing design or, if need be, on a secondary, detached structure, like a garage. In any case, we had an interesting situation here a couple days ago. I'm not sure of the specifics yet as the fire dept continues to investigate it. We have a Walmart in one of our suburbs where the solar panels, on the flat roof caught fire and did a good amount of damage before the fire was contained. The store has been closed since and will be for several more days, maybe weeks.

Gordy

I think any roof fastening method is prone to leakage, and fatigue at the point of penetration of the roof plane. Don’t forget wind loads, snow loads, and expansion contraction over a long period of time. It’s not just the weight of the panel assembly. A leak is a leak even if it’s 20-30years down the road. The potential damage is just as great whether it’s year 1, or 20.

Leonard

Fire ......Problem with the core solar panel is they continue to make electricity until you put them in the dark. All you can do is put a disconnect switch on them to stop them from sending that power down wires and out of the core cell array in the panel

Hopefully they have some type of thermal fuse in them to diconnect the cells internally if a fire. But I'm guessing that may be hard to do since panel likely run hot in summer.

Fred

The other thing is, I understand the panels need to be cleaned a couple times a year or they lose 15% to 20% of their collection capacity. Roof mounted makes that a tough job.

hot_rod

My mount method, shown below, at least for the heavier, larger thermal panels is to either J bolt under a rafter, or put strut or 2X4 under at least two rafters and bolt down into that.
Lags into roof sheathing or even rafter edges is not sufficient for wind and snow loads. And use engineered screws not hadware lags as you can see in the article.

If the PV modules are flat to the roof pitch that eliminates wind load, but snow load can shear or pull fasteners also.

Florida has a very strict mounting code and collectors and mounting need to be certified to something like 160 MPH winds.

Of all the various glues and adhesives I found double sided EternaBond mastic tape is the best, seals well and winds around the fasteners as they go into the holes.

Flashings are a must, no need to just screw into shingles, lots of options for all the roofing materials.

Here is a link to a good article on mounting to roofs.

D107

All great comments. These panels each have their own micro-inverter so there's no big 600V DC trunkline. Fire risk much less. @Leonard --the between rafters wide board you're talking about is called a 'purlin' I think but that can't be done here since under-decking is filled with closed-cell foam. Good point @Gordy about problems down the road, though the company says for all their 15 years they've had negligible issues with leaks. Our roof is 8/12 pitch (33.69º). Company claims rainwater keeps it clean; perhaps these very new panels (22.2% efficiency, 360w each) have a sheen on them that facilitates that; older panels did need cleaning from what I've heard.

AnthraciteEnergetics

I installed a 2.6 kW system last year. Myself, no installer, 9:12 pitch composite roof facing 240* in Northeast PA. Will yield around 3 MWh/year. Cost $1.10/watt - 6.5 or so year return on investment. We have net metering 1:1 until you produce more than you consumed in a year, then it drops to wholesale payment (7 cents or so)

Enphase microinverters mounted under each module on the roof. They convert the DC from the modules to AC and feed via THWN in PVC conduit into a double pole 20 A breaker. Electrical is very simple - no transfer switches, no batteries, no long DC wiring or combiner boxes, no large inverters. The "backfeed" logic is built into the inverter and is a trivial matter since it is an elrctronic device not a mechanical generator. Nothing to freeze, no moving parts.

If you are hooked up to the grid, batteries are extra cost. I'm not aware of many places in the US where the grid is so unreliable that you could justify batteries in a grid-connected situation. Generators are inexpensive enough for the occasional outage.

Leonard

Cousin is 5 miles from me, along wooded road, lot of outages from wet heavy snow breaking tree branches. . Niece in law is in heavily wooded Maine, they have many outages in winter from ice/snow falling branches/trees . They're at end of utility 25 mile" extension cord", lot of peninsula like land on the coast there. So they had to plan the house to not depend on power (except the well). Propane stove, oven ,water heater, wood stove ......

She has mini inverters on backs of her solar panels, For situations like that would be nice to at least be able to make your own power during outages in daytime ( no bats). Sounds simple for manufacturer to design that into the inverter, so I'ld ask manufacturer about that option.

Gens are fuel HUNGRY , they only are cheap if only run them a few hours. Bump into a bad multi-state ice storm outage and need 24/7 power for 1-2 weeks and your looking at ~$350/week fuel bill for 7kw gasoline gen at 1/2 load. $175 at almost no-load

D107

As mentioned earlier in this thread, there is some prohibition on using solar generated electric during outages in order to prevent live voltage from reaching outside workers repairing the lines. Not sure if this applies to stored electric in a battery. I've been told the solution to this may be some kind of way to isolate the internal electric from the outside lines.

hot_rod

most all code approved inverters and micro inverters have protection against back feeding. You are also required to have a labeled manual disconnect outside the building for utilities to disconnect the system from the grid.

D107

Thanks @Leonard and contributors for this thread. Re your thread title 'pull the trigger or wait' for me it's not a question of waiting for higher efficiency panels. The proposed company and system have high ratings, and financials--with a ROI of 7 years--are quite favorable. But after some serious thought, I have pretty much decided to look into community solar.

1. My roof is 5.5 years old; the last one lasted 17 years. Regardless of the current 'lifetime' warranty, if past is prologue my roof will need replacing in 11.5 years. At that time the panels will need to be removed, then re-positioned after the new roof is on. That's got to cost a few thousand. So 36 holes will have to be filled, then a new set of 36 holes drilled. Even assuming only drilling into rafters, that would have to done perfectly dead center to each rafter which in this old house are not always exactly 16 or 24 on center. As for fastening into decking, I know the condition of that decking will not support that, and given the closed-cell foam underneath, backing struts/purlins are not possible. If I had a standard attic where insulation was in the attic floor and the underside of the decking was more accessible I would consider doing it, esp since I could detect any leaks far more easily.

2. Despite contractor's claims of maintenance being unnecessary, judging from the dirt that gets on our siding every year from diesel particulates, sap, dust etc. those panels will get dirty. (We're very close to a train station.) Cleaning several times a year would be an added cost. I look forward to hearing about your decision Leonard.

Gordy

Shingles are a crap shoot, and the warranties are prorated. So basically worthless. I’d also be curious to know how a warranty claim would be fielded with solar panels in the mix. Shingle manufacturers can dream up all kinds of reasons why their product failed, and it’s not their fault.

Definitely something to think about before throwing panels on the roof.

Gordy

Could go the Elon Musk route, and kill two birds with one stone, and a life time savings, or mortgage. Lifetime guarantee.

However there seems to be a shroud of secrecy as to what is all included, efficiency, and what the lifetime warranty covers.

D107

@Gordy, Contractor says they would write a note attesting to non-damage to roof by panels, but roofing installer or manufacturer certainly won't be bound by that. Installer warranty was only five years anyway, so that's gone. One could get a letter from the manufacturer, but as you say, with the warranty being pro-rated and for materials only, you'd have to pay the labor for any actual repairs. Not sure what Musk is selling, but the fine print is always interesting if you can get a magnifying glass strong enough to read it.

Gordy

Solar PV shingles.

D107

From what I have heard solar pv shingles are not yet ready for prime time. I'd hope in the future that all shingles, siding, train, plane and car surfaces and even our clothing might be solar PV-able.

Leonard

I don't know solar. Run the cost numbers, but I'ld say don't wait for new higher efficiency panels unless something much higher% will SOON be in production. New stuff will come out for the next 300 years. Problem is the higher % stuff will always command a higher price, so current production stuff likely has the shortest break even time.
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All in all I'ld consider solar, but think I'm too old for it. Run the numbers for cleaning costs for when you get old and can't climb roof. Or estimate lower KWH production and new "break even year" if you can't clean it. I think biggest issue will be structural loads on roof, leaks, and cleaning. Also ask about costs of inverter replacement when nearby lighting stikes create spikes that fry the electronics. Also your city's building dept will likely require a letter from a civil engineer licensed in YOUR state saying the equipment will not overload your building structural rafters/supports and complies with structural codes (no overloaded stresses).
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Have not looked at shingle solar, sounds promising but devil is in the details. Sounds like a LOT of interconnecting wires to keep dry.
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From what I've read in an electrician's magazine (EC&M) code ONLY allows solar systems to backfeed power to utility street lines WHILE utility has power. Solar MUST automatically stop backfeeding the street utility within X seconds if utility power stops ( goes below some certain voltage). Seems reasonable to also require outside manual switch in case electronic failure prevents auto shut off.

That is not to say solar system can't provide power to building during utility outages, it just can't backfeed it to the utility street lines. This is to protect utility line repairmen from electrocution when working on a line they thought was dead, which has happened due to backfeeding.
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As far as closed-cell foam preventing installation of 16 inch long structural wood between ratfers ......it sounds easy enough to dig it out in places to install wood. Installing sister rafters whole length of rafter is another matter , but can also be done, just more work. Had tenant that had to do that when hanging heavy restaurant hoods off rafters.

Good luck with leaks. Solar and roofer may just point the finger at each other......in real life they both may be partially right. Now your into negotiating .....

As far as warentees, READ the contract. You will likely find bunch of loopholes that prevent liability. A good businessman will have laywer write it up so it's almost useless to you.

I read manufacturer's warentee on a 40 gal water heater. I would have to pay for removal and shipping it across the country for manufacturer to inspect it to decide if it was their defect before they would refund me ONLY what I paid for it . Since shipping was almost cost of the heater, the best I could hope for was to ~ break even on shipping. Useless warentee

Sorry for length ,lot to consider

jumper

What may very well happen is that fixed delivery cost will increase drastically while energy cost may decrease. Electric utility requires revenue one way or another.

PV is probably most practical where electricity is very expensive like in rural Ontario. Many homes there are electrically heated to boot. Thermal storage is obviously more economical (and more efficient) than batteries. Remaining question is what sort of thermal storage? Hot water,hot fluid,hot solid are some options.

Fred

A solar shingle installation isn't what it sounds like, on the surface. It is not a complete re-shingle on a home. You buy and pay for the capacity needed and the installation involves cutting out a section of conventional shingles and inserting the solar shingles. What that means is that you now have a seam, all the way around those shingles that are subject to a leak. They are less obtrusive from an appearance perspective but they have their own set of issues and they don't come in colors (yet).

hot_rod

Gordy said:

Solar PV shingles.

Or a metal roof instead of shingles.
My first home built in 1982 still has the first blue metal roof, although very faded


I've heard the red tile roof you see in Europe are considered 50 year roofs. Some are much, much older.

Clarence Beaver built a home in NC back in the 1970's I believe. he recessed the thermal collectors into the roof and shingled around them, a completely flat plane and able to be re-roofed.

Then again in 20 years... will you still be in that home?

Fred

Clay tile roofs are beautiful but they too have their own set of issues. I own an apartment building with a clay tile roof on it. They can last up to 100 years or more but they are held in place by a single nail and it's really the life of that nail and the deterioration of the felt paper under the tiles that fail, more so than the tile itself. Not to mention when it needs a repair, someone has to know how and where to walk in them or they break. I have four tiles now that need to be re-seated as they have slid over the winter.

Gordy

Or if you have bats

https://www.youtube.com/watch?v=Oc8ACBiwIyE&feature=share

Gordy

Tesla’s solar shingle is a complete reroof design.
https://www.tesla.com/solarroof

AnthraciteEnergetics

@Leonard I those cases a hybrid on/off grid system would be ideal (they exist). If you're going to do that, I would just get rid of the utility service and go full off grid if it's off and on that much. Gas engine gensets are about 15% efficient - probably 50 cents/kWh in fuel cost alone.

the_donut

> @AnthraciteEnergetics said:
> @Leonard I those cases a hybrid on/off grid system would be ideal (they exist). If you're going to do that, I would just get rid of the utility service and go full off grid if it's off and on that much. Gas engine gensets are about 15% efficient - probably 50 cents/kWh in fuel cost alone.

That's fine if you are far enough south. Here in NW indiana we can sell back during the summer but have to buy back during the winter.

Leonard

fuel cost.... yes 15% max efficient ( but only at full load, less at lower loads)

Using my 7kw Onan 7NHM gen...... 0.4GPH @ no-load, 1.3 GPH full load.
If drawing only 1 kw .....$1.32/KWH ..........maybe 5% ? efficient
If drawing full 7kw ....... $0.46/KWH .......~ 14.5% efficient
Cost to run at no load ....................... $1/hr = (.4gal/hr)* ($2.50/gal)
Assumes $2.50/gal gasoline. need to go to diesel better $/KWH

Use a liquid cooled gasoline engine and can get ~ 53K BTU/hr out of cooling water alone, at FULL load ( 7kw gen). More if you heat exchange the exhaust.

jumper

Leonard said:

fuel cost.... yes 15% max efficient

Use a liquid cooled gasoline engine and can get ~ 53K BTU/hr out of cooling water alone ( 7kw gen). More if you heat exchange the exhaust.

CPH with the power going to heat pump can be more than 100% efficient in terms of heat production relative to heat content of fuel. May very well be economical for people who like to service their motors themselves.

D107

So to continue with new info on the issues I've had with PV installation:
1-The penetration and leaks issue is still of concern, however it has occurred to me that the installation of the roof itself put hundreds of nails into both the decking and the rafters, but because of the overlap system, no leaks. Fastening the PV frames is a bit different of course--penetrating through both shingle layers, then adding the flashing and mastic but with our 8-12 pitch, it seems a little less worrisome than it did a few days ago.

2-I spoke with the rep about the issue of panel cleaning. It seems what they really do is spec their systems very conservatively, so in effect you will get more kwh than you expect and that is what will take care of any decreased output due to dirt or dust on the panels which will surely accumulate. And this can be done without significantly oversizing the system. That sounds reasonable as long I continue to get the total required annual kwh, and in some ways it may be better to avoid washing the panels too much--the less handled the better.

3-As far as having to remove and replace the panels when our roof needs to be replaced in 12-15 years, rep claims that because most of one side of the roof is covered by panels, it is protected to a great degree from heat and sun––though rain will still flow over shingles––so replacement should be delayed quite a few years. But at any rate, cost for panel removal and replacement doesn't sound prohibitive.

4- The real issue I've seen online is that even the top-rated installers or manufacturers have many complaints on service, especially when the manufacturer is doing parts and service and is halfway across the country. The delays are lengthy. A broken micro-inverter sometimes can take months to get repaired and you're out that amount of electric with no recompense. In my case the installer handles the 25-year warranty but who knows how long any one company will be in business? I'd want to find out how many repair crews they have on the job.

So all this and I'm also thinking alternatively of community solar (buying into a solar farm) or drainback solar thermal panels to integrate into heating system.

Leonard

As far as a fried micro-inverter maybe buy a spare now. What do they cost?

Doesn't cover the lighting issue since likely most will all blow if a strong voltage spike. Ask them about that. I'm wondering if a 1 ft dia loop on output wire will decouple the panels from any FAST rise time spike coming in on the utility line. (Loop has inductance.)

They use that trick to get lighting strikes to radio antennnas to not come into the transmiter building. Need to provide an alternate path to earth for the lighting, lighting gap (arrestor)

Reason this trick works is : When installing lighting arrestors on a roof, the down lead to ground rod can't have any bends under ~ 6 inch radius or lighting will arc across the bend. ( FFT of lighting has VERY high frequency components. So inductance of the bend makes very high voltage drop across the bend, that voltage exceeds the air breakdown voltage so lighting takes the path of least resistance and arcs over the bend instead of thru the wire)