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Old 06-13-2015, 10:51 AM   #81
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Another problem I have with putting up an PV system is that I do not think that I would get my money back when I sold....

IOW, think about it.... 15 year ago someone put up a system... cost them a bundle.... now they want to sell their house... but a new system would not cost anything close to what they paid... so why pay them anything for their expensive system that has all that 'old' technology

I probably will not be living in the same house in 15 years....
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Old 06-13-2015, 11:00 AM   #82
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Quote:
Originally Posted by ERD50 View Post ...

if we are going to subsidize solar, it should be based on an estimate of the system's annual production, rather than the system's cost.
It is, indirectly. ...
And that's the point - it is too indirect. It should be tied directly to output (or some weighted measure of output and pollution offset).

People are putting in solar in less optimal areas. Hey, if they want to do that, it's up to them. But why should we pay for the installed cost, rather than the 'green' energy it produces (if even that, but I'm taking that out of this equation, and assuming we support/accept subsides, but are looking for getting the most bang/buck from them).

-ERD50
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Old 06-13-2015, 11:00 AM   #83
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My only experience with solar panels is about the panel that I installed myself on my RV. Back then, I had problems buying a single panel without paying a lot for shipping, so got a used 215W panel locally and paid $240. It's a good brand name and German-made.

The panel never puts out anywhere near 215W, but then it was used and perhaps replaced and discarded under warranty. But one thing I observe is that at home where it is hot, the panel puts out 123W under direct sun and clear sky, but 143W when I was in the NW and under less than perfect lighting condition.

Then, I remember reading about solar panels losing efficiency when hot, in fact the colder it is the better the efficiency if the lighting stays the same. For each degree C rise, the panel may lose 0.5%.

I climbed up to measure the temperature with an infrared thermometer. The ambient air was 105F, but the panel was 149F, or 65C! The panel ratings are always at 25C (77F). Where I am, if it gets that cool I do not need power that bad.

The above is another factor that affects the output one can get from solar panels.

PS. I use a brand-name MPPT (Maximum Power Point Tracking) solar controller that can modify the load it presents to the panel, and can extract the maximum power with an efficiency of better than 95%. It does that by seeking the operating point on the panel I-V curve that maximizes the product of I and V (current x voltage = power). I have attached an ammeter and voltmeter to the set up, and watched it sweep the range every few minutes to find that optimal point. Modern microinverters like the Enphase all do this.
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Old 06-13-2015, 11:07 AM   #84
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IOW, think about it.... 15 year ago someone put up a system... cost them a bundle.... now they want to sell their house... but a new system would not cost anything close to what they paid... so why pay them anything for their expensive system that has all that 'old' technology
If the original owner has already achieved "payback" in saved electricity costs (with all other factors considered), then any increase in the home's value is just gravy, right?
From the new buyer's perspective, the owner can show the electric bills and kwh produced by the existing array, that is worth something to the new buyer. Yes, he could buy new panels, but these are already there and installed and have an expected life of at least 10 more years (at which point the buyer can get even >better<, cheaper ones than he can buy now). And, if they come with the house, any extra he pays gets added to the mortgage, which is usually cheaper financing than can be got elsewhere.

I would be worried about whether the solar panels will cut down the pool of buyers who would consider the property. Will 50% of potential buyers see 'em as a fussy, troublesome eyesore, or will the majority of people see it as a plus?
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Old 06-13-2015, 12:07 PM   #85
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Originally Posted by Texas Proud View Post
Another problem I have with putting up an PV system is that I do not think that I would get my money back when I sold....

IOW, think about it.... 15 year ago someone put up a system... cost them a bundle.... now they want to sell their house... but a new system would not cost anything close to what they paid... so why pay them anything for their expensive system that has all that 'old' technology

I probably will not be living in the same house in 15 years....
You fail to realize the system already paid off the capital investment to install probably about year 7 or 8. Meaning, you are probably just as likely to not want to leave the panels behind for a buyer, but take them with you. After all, they not only paid for themselves 7 years ago, (your 15 year scenario) but they made you a load of money in the energy bill savings.

The old system is worth it's monthly utility bill savings.
New systems might be marginally cheaper than today, but not enough to matter or else the entire utility industry would collapse.

Your solar generation savings on your electric bill is tax free money in your pocket. Compare that to a tax deferred investment and see where your money is better held over 15 years when it comes time to actually spend it.

Think of solar as you would any home energy saving upgrade. What if you could spend $10,000 on a home remodel that resulted in your electric bill dropping from $150 a month to $5 a month? The return on that investment is obvious. Just because at some future date, like 15 years down the road, the remodel might only cost $5,000 doesn't do a thing for you today.
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Old 06-13-2015, 12:27 PM   #86
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If he sees this post, perhaps our longtime solar user Nords can help out with his voice of experience on this subject.
Thanks, Sarah. Busy thread.

We went almost completely DIY with used panels. We had to use an electrician for the permit and the net-metering agreement but now I do all the work on my own.
Extreme home improvement: DIY photovoltaic array - Military Guide

Here's the math:
Extreme home improvement: the finances of your residential photovoltaic array - Military Guide
We installed just over 3300 watts between 2004-2007 for just under $16K (plus sweat equity) and got back over $9K in federal/state tax credits. Our sweat equity paid for itself by late 2010.

(BTW renting [a power-producer agreement] might be just as cost-effective, although it has its own issues. This is a guest post from one of our own forum members:
The Bright Side of Solar Power Purchase Agreements - Military Guide
)

Here's an update on those posts:

In 2011 we renovated our familyroom and elected to remove our system to add more reflective insulation to our south roof. When we reinstalled our array I bought a modern flashed-mounting system with two rails. It was cheap and easy to install, but it also gives us more flexibility in swapping out panels or expanding for more capacity. The images in those linked posts show our old configuration while the photos below show the new layout. The larger panels are 115 watts (10 years old) and the smaller ones are around 50-55 watts (20-25 years old). If I rebuilt the system with 2015-tech 350-watt panels then it would take up about a third of the roof space.

We went with a string inverter in 2004. The microinverters are fairly new but the bugs seem to have been worked out. An early problem was that panels were rated at 315+ watts while microinverters topped off at 270-300 watts. That might have been fixed but it's important to make sure that the microinverter is big enough to not just clip off the panel's power output. For larger arrays, it's also important to compare the price of the microinverters to the price of a large string inverter. The microinverter may be more efficient (I'm skeptical of the magnitude of the difference) but it might still be more expensive even after the efficiency is included in the price comparison.

A few months ago our 10-year-old Xantrex 3000-watt grid-tied string inverter died. It was $2500 new. The problem was in the AC side, it kept blowing its output fuse, and I couldn't find the fault. For $2861 we bought a SMA Sunny Boy 4000-watt grid-tied string inverter. The tech difference is amazing-- not just more capacity but better DC-->AC conversion circuitry, two MPPT trackers instead of one, eight strings instead of two, a modern display/interface system, and even a better DC connection box.

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Originally Posted by folivier View Post
Can you direct us to this system?
I would love to do solar but would really like a hybrid system that can be used in power failures also.
Best of all, this Sunny Boy has a small "Smart Power System" feature with limited off-grid abilities. When HECO goes down I can shut off the inverter's grid circuit breaker and flip the switch on the SPS receptacle. The inverter puts out up to 1500 watts at 120V AC (sunshine permitting), which is enough to run an aquarium air pump and the AC pump on our solar water heater. It might even run the fridge, although a fridge compressor startup surge will hammer the inverter's ability to maintain a 120v output. When HECO comes back up, I can turn off the SPS receptacle and shut the inverter's grid circuit breaker again.

$2500 in 2004 dollars for the Xantrex is about $3300 in today's dollars, so we technically spent 15% less today for the Sunny Boy. It's the equivalent of upgrading from a 1980s PC XT running DOS to a multi-core Win7 machine with a SSD and extra RAM.

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For a hybrid system that can be used in power failures, the configuration is a bit different. Most house back up is via battery. The plant I'm looking at has AC right from each panel, so batteries is going to require that AC be converter to DC, then back to AC again. Lots of hardware and overhead expense. Also, batteries are not cheap and must be replaced within every 10 years. Tesla is building a house battery system, but 10kw is over $3,000 and not anywhere near cost effective.

With that said, there is a split system that saves the final DC to AC conversion to a central inverter, still using the MPPT and the DC to DC converter at the panel and saving the line losses.
Here is a 5kWh system that does that;
16 Panel SolarEdge / SolarWorld Grid-tie System - Wholesale Solar

The panels are built in Oregon, starting at the silicon level on up.

The kit price is $9,111. You would have to add sales tax and shipping depending on your location to the FOB which is Lake Shasta, CA.

With a sales tax of 7% and an average shipping cost of $500, you could expect to pay $10,250. Subtract the Federal tax credit of 30% and it's a net cost of $7,175. Figure in incidentals; permits, conduit, etc. of maybe another $500, and hire an electrician to lend you a hand for the two days to install, $1,000 and you are still under $10,000 for a 5kWh plant that will reduce your utility dependance by 8450kWh per year. (Based on a latitude of 38 degrees, panels facing 180 from North and a tilt of 22 degrees.)
Compare that generation to your own use and see where that puts you. That link has tabs for other options and sizes for solar kits.

The kit I am interested in with USA built micro inverters and panels is found here, but I'm needing it customized for an 18 panel solution and that falls between their 15 and 20 panel kits;
Enphase Energy Expandable Gridtie Solar Power Systems

The neat thing about this option is that you can start with a starter kit and just buy panels and microcontrollers to build it out. Plug-n-play. Everything is contained in each panel.
I think the reality of grid-tied vs off-grid is a little more nuanced, and so are the other factors in buying a system.

For example, PV panels are a commodity. We have the Chinese solar-panel industry to thank for crashing prices to under $1/watt, and their industry is paying the price for that overbuilding. Instead of buying the latest & greatest, try eBay for last-generation panels or factory seconds. You'll get a huge discount over buying used/dinged panels just as you would for buying a used car.

"American made" might be important for morale, but there's little difference in panel output or lifespan. Much of the R&D is American, and it's far more cost-effective to outsource the manufacturing. I don't worry about finding American-made oil or American-distilled gas for my car, and I don't worry about what country makes my PV panels.

Buying off-the-shelf arrays (with installation) is ridiculously easy. (Hawaii alone has over 200 PV installation businesses.) Installing your own system is within the capability of an electrically-safe DIY homeowner, but you'd still need a construction permit and an electrician's signature on a net-metering permit.

But if it got to the point of custom-configuring a retail system then I'd simply buy my own panels (eBay or local supplier), buy my own inverter(s), and find an electrician willing to do their part (at an hourly rate) while I take care of drilling holes in a perfectly good room. I'd even connect the panels & inverters with wiring and connectors made up from our local supplier... but these days that might also be available in pre-fabricated lengths sold online.

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Originally Posted by AllDone View Post
I understand that solar panels are a popular asset with potential house purchasers so you can consider that they add value to your home for potential re-sale.
It's just a feature. Some homebuyers can do math and will pay extra for the PV system, while other homebuyers just like the kitchen appliances and won't appreciate the PV system. They might even argue that it's a maintenance liability.

I would not install a PV system expecting to raise the value of my property. Buy (or rent) a PV system for the financial payback.

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Originally Posted by samclem View Post
The info about the panels with the mini-inverters is pretty cool, and the relatively low cost per watt these days.

I wonder if it might make sense to build your system to something well below 95% of your present usage. Given the current rate structure, you save the most money by reducing your use over that present low base rate of 200-300 kwh. The payback period for the "extra" panels that replace energy now sold for 13 cents per KWH must be fairly long. Now, that's all present rules and politics, but given present California proclivities and demographics, it might be a safe bet to assume there will continue to be a lower rate for the first few hundred kwh while the "fat cats" pay higher rates. Also, it might be fair to guess that there will be continued improvements in A/C efficiency, appliance efficiency, etc, so having fewer panels might make sense even down the road. If there's a cutback in the net metering generosity, one obvious option would be "no sales back to the grid that exceed the customer's use." If that happens, any money spent to buy capacity beyond your (possibly lower future) needs is wasted.

Environmental laws, special rate programs, court rulings: So many of these factors are artifacts of your political system, not market forces. That makes the future very hard to predict.

Lots of folks said that about oil prices, too.
Again, thanks for the info, and good luck.
I've given up trying to predict electricity prices. Hawaii's prices fluctuate with the price of oil, and we don't have time-of-day metering (yet). Inflation has been unpredictable, too, and when oil prices start to rise then the alternatives (LNG, biofuel, PV, wind, OTEC, even geothermal) start to enter the competition.

Tax credits have been on the brink of expiring at least three times in the last decade. Maybe they'll be extended after 2016, or maybe not.

I think it's reasonable to factor the CPI into energy prices (and maybe the opportunity cost of buying a PV array instead of a nice blue-chip dividend stock) but otherwise you subtract the tax credits and do a straight payback calculation.

As you've pointed out, it's far better to reduce your consumption than to raise your generating capacity.

Most net-metering agreements only reimburse the owner for what they use. (HECO carries our excess production over a rolling 12-month period.) If you make more than you use then you'll eventually give it away for free. If you become a wholesale producer then it's an entirely different price (a fraction of retail) with extra tariffs, and for homeowners it's not worth the price.

We use all the usual tactics: solar water heating, tinted double-pane low-e windows, wall & roof insulation, EnergyStar appliances, line-drying our laundry, tradewind cooling, CFLs & LEDs instead of incandescent bulbs. I even have SSDs in our household computers instead of spinning-platter hard drives. However our biggest energy-efficiency improvement has been launching our daughter from the nest. Today our biggest indulgence (by far) is a DVR and an aquarium air pump. When my spouse eventually upgrades her CRT TV to a Smart TV then our energy use will probably drop again.

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Originally Posted by ProspectiveBum View Post
Doesn't that assume that you have no maintenance expenses, and that the panels maintain the same level of efficiency over that 25 years? Is that likely? Most of the electronics I purchased 15 years ago have already been retired, and those don't sit out in the elements 24/7.
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This is one reason that the roof of a dwelling is not an optimum place for a solar array. I'd feel better about putting a solar array up there if I had a metal roof (50+year life). Another option is an outbuilding/shed that can be put where there is the least shade/best angles for catching the sun, and can have a metal roof.
"Maintenance expenses"?

I have never cleaned the cover glass on our PV panels-- the rain does that (even for bird poop). I've never done any maintenance on the hardware or wiring itself. Our system has seen hurricane-force winds, hail, torrential rain, vog, and (of course) lots of sunshine. The aluminum frames and the cover glass look fine. I wish I knew what killed our Xantrex, but it wasn't a lack of maintenance.

Most manufacturers show projected panel performance of 20-25 years before output starts to roll off. (The tech changes every 5-10 years so it's difficult to predict the reality.) Our 25-year-old panels are starting to show signs of rust under the cover glass, and I'll probably replace five or six of them with one 300-watt panel (from Craigslist or eBay).

A rooftop of PV panels will actually prolong the life of a shingled roof, but even so you might reasonably expect to get 20-25 years out of your average roof.

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Originally Posted by Texas Proud View Post
Thanks for the info....

So, solar cannot work without a line charge... so if there is a power outage then you do not get any benefit of having solar
I guess unless you get off the grid that is....

Does that mean all solar just connect up to the breaker box?
As others have mentioned, a grid-tied system is cheaper but it needs the electrical utility's voltage before it'll run. Some modern inverters will do both (with limited capacity). However even an off-grid inverter on its own will struggle to maintain steady household voltage if a large surge load (fridge, air conditioner, vacuum cleaner) starts up. A large bank of batteries can help an off-grid inverter maintain house voltage under almost any startup surges, but that also gets more expensive.

Our house feed from HECO is a 100-amp breaker. The same bus bars have a 20-amp breaker (next to the 100-amp breaker) that feeds our inverter's output into the house and grid. Electrical code also requires a manual disconnect, but grid-tied inverters have their own circuitry to shut off when the grid goes down. Our Sunny Boy SPS receptacle is wired directly to the inverter and won't come on unless I flip a switch on the receptacle. That switch turns on the receptacle and also electronically disconnects the inverter from dumping power into the circuit connected by the 20-amp breaker.

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Originally Posted by NW-Bound View Post
I am seriously tempted now to get just one panel and one microinverter, spend 1 hour to wire them up then to record the power output to see what kind of output I can get over a day of summer, a month, a year. It's as you say, an interesting hobby. And if it looks promising, I can scale it up.

Here's the cost: 1 250W panel ($275 new, $180 used), 1 microinverter ($155), a 110/220 1kW transformer ($45), hardware ($10). Total: $380-$485.

The transformer is needed because I want to plug this into a normal wall outlet of 110V, while the microinverter works with 220V output. This allows me to use a common Kill-a-Watt to log the power output.
Better yet, I think you could monitor the microinverter over its powerline network interface.

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Originally Posted by Mulligan View Post
The 800 pound gorilla hiding in the closet though appears to be this, and I do not have an answer for mind you. Lets say that a significant number of people "go solar", but still stay connected loosely to the grid. Average daily power consumption need from the Utes goes down significantly. However, PEAK maximum backup power from Utes is still necessary if not mandated. This would cause a tremendous increase in cost per kilowatt as peak backup power is expensive in itself to maintain. If successful meaningful battery backup power is not invented the costs for maintaining the grid will still be fixed and at a higher cost.
I don't think we would immediately see the death spiral of Utility company viability because the grid will still be needed. So I wonder if the costs will just be shifted to higher monthly connectivity fees, thus negating a big savings in going solar?
Yeah, that's an issue.

I think PV tax credits will come under more attack from the states, and eventually even from the federal govt. The subsidies helped jumpstart an industry and drive prices from $10/watt down to $1/watt, but further subsidies are arguably of little impact.

HECO is already whining about us slimy net-metering customers not paying their fair share for the grid. However HECO's CEO earned nearly $6M last year, so I have a difficult time feeling guilty about my own selfishness. I've also watched HECO waste millions on flawed engineering analysis and dubious reliability/redundancy upgrades, so I'm skeptical that our grid-tied vampire behavior is worse than their bureaucratic and operational inefficiency.

In other words, they need to fix their own house and run it more like a business (and less like a government agency) before they come after us little guys.

Our house was net-metering agreement #26, and today Oahu has tens of thousands of net-metered installations out of more than a million customers. In other words, they're hysterical about fewer than 5% of their customers. If HECO adds a feed-in tariff then I'll grudgingly pay it. But first I'll do the math and compare HECO's price to the long-term cost of lead-acid batteries or Tesla PowerWalls.

Electricity is a commodity, and I'm not going to pay for infrastructure any more than cell phone users want to pay for a landline telephone. Even our local landline phone company has figured out that its customers will still pay for IPTV and fiber-optic Internet access. Maybe HECO will come up with a similar business model that extracts the last penny out of their infrastructure.
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Old 06-13-2015, 12:40 PM   #87
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...
Better yet, I think you could monitor the microinverter over its powerline network interface...
Yes, as DaveMartin has with his system. Alas, that interface costs $600, a bit high for my experiment with a toy.

If I am to install a system, the Enphase microinverter is the way I would go, compared to a string inverter. The microinverters will each optimize to the individual panels, plus individual failures will not be catastrophic.

My tile roof and its suboptimal orientation are the two main detractors. My roof has had a few leaks, costing several $K for repair. I still have not remounted my solar water panel since that repair.
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Old 06-13-2015, 12:50 PM   #88
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Yes, as DaveMartin has with his system. Alas, that interface costs $600, a bit high for my experiment with a toy.
Yep. I've never bothered to connect our inverters to my PC or my website, either. I like tracking the monthly performance, but that works just as well with a pen and a spreadsheet.

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If I am to install a system, the Enphase microinverter is the way I would go, compared to a string inverter. The microinverters will each optimize to the individual panels, plus individual failures will not be catastrophic.
Enphase makes a good microinverter. At under 4KW, assuming 300-watt panels (or bigger) matched to the microinverter's max capacity, they're probably cheaper than a string inverter. But for bigger systems it might be worth buying a string inverter just because of the pricing.

Over the (at most) 100-200 feet between the panels and the house's AC circuit breaker, I don't think there's a meaningful financial difference in conversion or transmission efficiency between "AC from the panel" vs "AC at the inverter".

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My tile roof and its suboptimal orientation are the two main detractors. My roof has had a few leaks, costing several $K for repair. I still have not remounted my solar water panel since that repair.
Ouch. There are tile mounts/flashings for PV arrays, but my impression is that they're (1) not cheap and (2) probably more complicated than the average DIY homeowner wants to tackle.

We found our water panels from Craigslist, and they're almost 40 years old. At $75 each it was worth buying two and installing them in parallel. If one starts to leak then I'll just shut off the isolation valves, remove it from the roof, and sell the copper for recycling.
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Old 06-13-2015, 01:41 PM   #89
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I have not been serious enough to price out different types of system, but what I like about the microinverter setup is that the panels can be added incrementally, and one also does not deal with high DC voltage as with a string of panels. And then, for less than ideal mounting situations where a panel may get partially shaded, or having a different orientation, a "weak" panel will not drag down the entire string as the panels are not connected in series.

I really like the microinverters and the current low prices, which start to make sense even without subsidies. I have also looked at tile-roof racks, but they are still pricey and not yet popular. Perhaps in a few years.

My roof leaks were not related to the solar water panels, though I did lose the panels earlier because of a freeze (due to my own negligence, a long story). I got mad at myself, and opened one up and rebrazed new copper lines into one, but have not remounted it after the roof repair. One of these days, when it is not 160F on the roof.
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Old 06-13-2015, 02:42 PM   #90
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But the payback way back when was not 7 years....

And where I live it is also not 7 years.... I have lots of shade and bad roof angles...
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Old 06-13-2015, 02:44 PM   #91
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But if you got your money's worth out of the utility bill reduction over 15 years, you are even. Any cent you get from the residual resale value is a plus.
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Old 06-13-2015, 03:14 PM   #92
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But if you got your money's worth out of the utility bill reduction over 15 years, you are even. Any cent you get from the residual resale value is a plus.
But if the payback was 15 years and it is now 15 years..... I have a net of zero... I took a risk and did not get any reward...


So, the only benefit would be any increase in selling the house...


Having a 7 year payback is easier.... but when I was at mega corp, they wanted a 3 year payback on an investment... never understood why as some investments would pay back handsomely over a 15 or 20 year lease... but not cover their cost the first 3 years...
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Old 06-13-2015, 03:46 PM   #93
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If one bought the S&P in 2000, he would have to wait more than 10 years before breaking even...

OK, just joking as the comparison is not apt.

I concede that solar power does take a long time to pay off, and is most likely not going to work out for someone who plans to move. As I intend to die in my current home, I would install one if only to have something to play with.

Rarely do I get a toy that promises to pay for itself with time, even if that's a long time. Most toys cost me even more money after the purchase for maintenance, and still end up in the trash.
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Old 06-13-2015, 08:28 PM   #94
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If one bought the S&P in 2000, he would have to wait more than 10 years before breaking even...

OK, just joking as the comparison is not apt.

I concede that solar power does take a long time to pay off, and is most likely not going to work out for someone who plans to move. As I intend to die in my current home, I would install one if only to have something to play with.

Rarely do I get a toy that promises to pay for itself with time, even if that's a long time. Most toys cost me even more money after the purchase for maintenance, and still end up in the trash.

Actually the small setup you proposed seemed like an interesting thing to do... I could put one on the back of my garage and plug it into the socket that is outside... but I bet I only get 2 or 3 hours of good sunlight with the houses and big pine trees around here.... I do not see any payback... so I would have to view it as a toy....
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Old 06-13-2015, 10:30 PM   #95
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Well, my setup to do this experiment may not be kosher, as it would involve plugging power generation into the grid without the utility's agreement. It is more than the usual safety requirement. Here's what I have found out.

Look at the chart I included in post #67 of this thread. My AC usage is a function of temperature, hence it does not drop off until 9 PM, way past sunset. If more people have solar, in the late afternoon their power output starts to taper off and the demand on the grid starts to ramp up, putting stress on the system.

So, the local utility now has a different contract to solar home owners to address that. They have a formula to charge for that excess demand you put on the grid. And they say that a way to alleviate it would be to have the panels facing west to shift the peak output towards the late afternoon.

See how complicated this can get?

So, I am pondering making my experiment an off-grid one. It's more along the line of what I have done for my RV, which has a solar charger controller, a 2kW pure sine wave inverter, a pair of batteries. Perhaps I can "borrow" equipment from my RV when not traveling. This is more work!

But how do I make use of the energy that I produce, as I cannot pump it into the grid? I now have to put in at least two panels, so that they produce more than 500W to allow me to run a small window AC as a load dump. This is getting more complicated.
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Old 06-14-2015, 12:20 AM   #96
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And then, for less than ideal mounting situations where a panel may get partially shaded, or having a different orientation, a "weak" panel will not drag down the entire string as the panels are not connected in series.
Even my 25-year-old panels have blocking diodes in them to prevent that problem. The voltage just passes straight through the panel, whether or not it's contributing to the electron flow.

I'm pretty sure that today's panels have at least the same type of circuitry.
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Old 06-14-2015, 06:55 AM   #97
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From the new buyer's perspective, the owner can show the electric bills and kwh produced by the existing array, that is worth something to the new buyer.
No, it's worth nothing to the buyer. A real-estate agent explained this to me -- about a furnace or hotwater heater -- when we were selling our house. A buyer expects a furnace & HW heater, period. If it is there and is working, that is enough to satisfy them. They will not pay any extra for a spiffy new high-efficiency furnace.


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I would be worried about whether the solar panels will cut down the pool of buyers who would consider the property. Will 50% of potential buyers see 'em as a fussy, troublesome eyesore, or will the majority of people see it as a plus?
99% of potential buyers will see them as a maintenance nightmare. And an eyesore. My Dad had solar panels on their house. They had to remove them to get the house sold.
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Old 06-14-2015, 07:30 AM   #98
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But the payback way back when was not 7 years....

And where I live it is also not 7 years.... I have lots of shade and bad roof angles...
Why are you even concerned with this then? If it doesn't work for you, don't do it. And certainly don't go back in time to wonder if you should've done it then. Makes no sense.
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Old 06-14-2015, 07:41 AM   #99
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Originally Posted by skipro33:
under $10,000 for a 5kWh plant that will reduce your utility dependance by 8450kWh per year...
That would save me $675 per year. 15 years to break even, if I ignore the interest & earnings on the $10K, or if I could get a 0% interest loan.
$675 for 8450kWh means 8c/kWh. That's fairly cheap.

Where I am, I can have a fixed (non-time-of-use) but tiered rate structure that would be about 12c average, or a TOU rate that's 7.41c off-peak and 22.26c on-peak. I chose the TOU because it actually saves me money. Solar production would fall 1/2 and 1/2 between two rates, so that's 14.8c/kWh.

So, the payback will vary with one's circumstance. In Hawaii and in places where the rate is as high as 30c/kWh, solar definitely makes sense.

PS. By the way, skipro location gives him 8450/5 = 1690 eq. max sunshine hours/year, or 4.6 hrs/day. That's reasonable. My location would give me 6 hrs/day, but the hot temperature in the summer may cost me 20% in panel efficiency.
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Old 06-14-2015, 07:53 AM   #100
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Even my 25-year-old panels have blocking diodes in them to prevent that problem. The voltage just passes straight through the panel, whether or not it's contributing to the electron flow.

I'm pretty sure that today's panels have at least the same type of circuitry.
But if the diodes have to kick in, it's too late, meaning the panel is already driven into reverse bias. And then, a 60 or 72-cell panel still has only 3 diodes, for 1 diode every 20 or 24 cells, because the panel construction does not permit 1 diode/cell.

Anyway, for more subtle panel-to-panel variations, let's look at DaveMartin's data.



His weakest panel produces 1.44 kWh, and his strongest 1.57 kWh. That's a variation of 8%. The total is 48.7 kWh, as shown at at the bottom left corner.

In a string, the weak panel will limit the total to 32 x 1.44 = 46.08 kWh. That's a 5% drop from 48.7 kWh. And then, what if the panels age differently and the weak one gets weaker?
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