Shading: Conflicting results

[rscott]

The above is absolutely wrong. I have over two years of data proving it is wrong. I would gladly invite you over to see my shade situation, see my Electric bills for the last three years and my solar production for the last two plus years. I could post pictures and video but it would not do it justice. I am not willing to spend the time to post all my bills, spread sheets, production, videos and pictures since it could easily be denied or argued. I will even buy the pizza.

Hi FFE,

I wanted to thank you for your original posting and this as well, it is appreciated. It took a while for me to figure it out, but J.P.M. and Sunking are operating on old rules of thumb -- "Don't install where there is shade" and "Don't install on north-facing roofs". I'm sure it works well for them. But just as I am stuck trying to make the numbers work, they are stuck on those rules of thumb -- to the point where they are willing to publicly call me a fool if I go ahead with it (even though PVWatts shows numbers that work for the north-facing roof, and if I can get the trees cut, it would be a "normal" installation).

Assuming I do go ahead with this (as I likely will, just not sure of the exact setup yet), I've been warned that I shouldn't be surprised if the numbers are worse (and potentially a lot worse) than what I am being quoted (and there is a chance I might be pleasantly surprised). That's good; that is what I need to hear.

[azdave]

To me, it is nothing more than an investment decision. Always has been.

I personally was at the yes/no decision point with a calculated 7-year break-even when I bought my system. With dumb luck, the payback time has actually dropped but it could have swung the other way since energy costs have not risen as predicted.

I can't imagine investing in a system that would be handicapped by shade unless the purchase cost was very low to make the ROI a safe bet. Like I said, it's an investment decision for me. I didn't install solar to be green.

I did not go back and read the whole thread again today. Did you mention expected ROI? If you look at the best case and worst case scenarios, how long until you reach a payback point? If it is more than 8 years I would invest my cash elsewhere.

I would never put solar on a house if I did not intend to live there at least 10 years past the ROI. I also would never finance or lease a system (or a car for that matter but that's just me).

[ButchDeal]

Hi FFE,

I wanted to thank you for your original posting and this as well, it is appreciated. It took a while for me to figure it out, but J.P.M. and Sunking are operating on old rules of thumb -- "Don't install where there is shade" and "Don't install on north-facing roofs". I'm sure it works well for them. But just as I am stuck trying to make the numbers work, they are stuck on those rules of thumb -- to the point where they are willing to publicly call me a fool if I go ahead with it (even though PVWatts shows numbers that work for the north-facing roof, and if I can get the trees cut, it would be a "normal" installation).

Rscott, JPM and Sunking are operating on actual measurable results. Their adjectives might be stronger than you would like but they know what they are talking about.

FFE is working strictly on his own one home and he is working on a single result. Further that result is slanted in that he has already sunk the cost into the system so he is trying to convince himself that it is great. He has no system information to compare it to for a point of reference, no base line. He has some production and he is happy with it. great for him
But his conclusions are vague and based on feelings, meaning they can not be transfered to actual results for you. His encouragement to proceed is the only thing you should take away.

As for PVWatts showing numbers that work, PVWatts is a simple model, you have to input the shadow percentage into it. Even the north facing roof is going to get effects from the shadows to the south, so like all models the results are only as good as the input into the model.

Everyone has expressed the same sentiment that cutting the trees is your best solution.

I've been warned that I shouldn't be surprised if the numbers are worse (and potentially a lot worse) than what I am being quoted (and there is a chance I might be pleasantly surprised). That's good; that is what I need to hear.

This is quite strange. Solar is one of the most straight forward things to model and predict (predicting a single days production is impossible without knowing the weather but general production with assumption of general weather is easy). Sales people use a rule of thumb, but the modeling software is relatively easy for experienced people to set up and get very accurate results.

We have installs with a single large tree in the yard that for whatever reason the owners do not want to cut. You can watch the shadow of the tree role across the array each day and the production tank as it does. They have a few hours of very little production. Yours would be the opposite, you would be lucky to get a few hours on any one module of good production and never the whole array at the same time (without tree cutting).
I would highly encourage you to look into cutting the trees particularly the ones to the south west which were smaller in your early satellite photos.
And work on a plan to keep them down. Then a design that uses the space cleared of shadows. You would still have the shadow in the morning from the older ESE (East South East) tree but at least you would have a consistent production time window after that.

[rscott]

...
I can't imagine investing in a system that would be handicapped by shade unless the purchase cost was very low to make the ROI a safe bet. Like I said, it's an investment decision for me. I didn't install solar to be green.

I did not go back and read the whole thread again today. Did you mention expected ROI? If you look at the best case and worst case scenarios, how long until you reach a payback point? If it is more than 8 years I would invest my cash elsewhere.

The payback period that is being calculated is 4.5 years. So that leaves a fair bit of margin for error (which can be mitigated with pruning and/or tree cutting, if possible). That compares to an 8-9 year payback I was looking at with solar back in 2011 assuming the trees were cut.

In my case, I'm willing to sacrifice the ROI to a fair extent if necessary, as I sense the importance of removing as much CO2 from the atmosphere as quickly as possible.

[SunEagle]

The payback period that is being calculated is 4.5 years. So that leaves a fair bit of margin for error (which can be mitigated with pruning and/or tree cutting, if possible). That compares to an 8-9 year payback I was looking at with solar back in 2011 assuming the trees were cut.

In my case, I'm willing to sacrifice the ROI to a fair extent if necessary, as I sense the importance of removing as much CO2 from the atmosphere as quickly as possible.

I understand your decision to go ahead with your installation. Just don't be too upset if that 4.5 years payback is longer.

As for removing as much CO2 from the atmosphere as quickly as possible I presume you do not drive an ICE vehicle and turn off all electrical appliances after the sun goes down. Those 2 actions will save more CO2 than having a solar pv system on your roof.

[bcroe]

My objective was to minimize liability to utilities, but managed to completely eliminate burning
fuel for heat and electricity, not even wood, not even nuke, no CO2. Yes this grid tie interacts
with the nuke down the road. But they are using less fuel than if I didn't exist, thanks to load
leveling and my annual surplus. Bruce Roe

[rscott]

As for removing as much CO2 from the atmosphere as quickly as possible I presume you do not drive an ICE vehicle and turn off all electrical appliances after the sun goes down. Those 2 actions will save more CO2 than having a solar pv system on your roof.

Great thoughts there. No on turning off all electrical appliances after the sun goes down, but yes on not driving an ICE vehicle (and like many EV owners, cannot imagine going back). I've got a Kill-a-Watt meter, but it has been quite a few years since I checked various appliances.

[FFE]

1. Rscott, JPM and Sunking are operating on actual measurable results.

2. FFE is working strictly on his own one home and he is working on a single result. Further that result is slanted in that he has already sunk the cost into the system so he is trying to convince himself that it is great. He has no system information to compare it to for a point of reference, no base line. He has some production and he is happy with it. great for him
But his conclusions are vague and based on feelings, meaning they can not be transfered to actual results for you. His encouragement to proceed is the only thing you should take away.

1. I believe everyone is basing their statements on data from trusted sources. However, the data is obtained using non real life scenarios. I spent hours looking for independent data on real life situations. I found one completed by an independent source commissioned by a panel manufacturer. However, I am guessing that the company that commissioned the test got to pick the panels theirs go up against. The test is closer to my results than to the tarp over panels result. I hope someone will post a link for me of a truly independent test with real shade not commissioned by a party with a vested interest.

2. Butch is partially correct. In the following thread you can see my optimism. However, in the end this forum helped me find as close of a base line as possible.

https://www.solarpaneltalk.com/forum/solar-panels-for-home/solar-panels-for-your-home/22747-anyone-with-wsw-array-in-socal

rscott, You are welcome. For me the reasonable worst case scenario was that I had to fight to get reimbursed for the guaranteed minimum. The absolute worst case was that the installer went belly up and I was stuck with a low performing system. I took the risk.

[ButchDeal]

1. I believe everyone is basing their statements on data from trusted sources. However, the data is obtained using non real life scenarios. I spent hours looking for independent data on real life situations. I found one completed by an independent source commissioned by a panel manufacturer. However, I am guessing that the company that commissioned the test got to pick the panels theirs go up against. The test is closer to my results than to the tarp over panels result. I hope someone will post a link for me of a truly independent test with real shade not commissioned by a party with a vested interest.

That is your OPINION. I know my data is based on as real life of data as you can possibly get, thousands of real installs all over the US.
I know and understand very well how NREL does their testing. I also have worked on patents for simulation and read and understand most of the papers on the same. This is REAL scientific data.

2. Butch is partially correct. In the following thread you can see my optimism.

Partially correct!?? funny.
I thought I was wrong once, but I was mistaken.

[SunEagle]

Great thoughts there. No on turning off all electrical appliances after the sun goes down, but yes on not driving an ICE vehicle (and like many EV owners, cannot imagine going back). I've got a Kill-a-Watt meter, but it has been quite a few years since I checked various appliances.

Unfortunately there are very few POCO's in the US that can honestly state that all their power is generated using RE. So most people do not understand that any use of electricity at night is more than likely coming from a fossil fuel power station. That would include charging that EV at night.

The simplest (although not always the easiest) way to reduce CO2 and electric power bills is to find ways to use less electricity.

[Mike90250]

The payback period that is being calculated is 4.5 years. So that leaves a fair bit of margin for error....

Then someone has either fudged your #'s. Payback / ROI / Break-even under 10 years is unusual. You are expecting less than half that, so be prepared for a surprise .

[FFE]

Less than 5 year payback is reasonable if electric rates are high, net metering is pro customer, you have more than just the federal tax credit in rebates, a roof that faces very close to due south, good tilt, simple install at a great price, aggressive load shifting, near zero shade, etc. or at least most of those. If that 4.5 years came from the salesman, well.... If you came up with that number, I recommend you double check that. I have only a little over half of the above and my worst case payback was 15 years. With the addition of an EV, changes in rates and better than guaranteed production my latest worst case prediction is closer to 12 years. Most people would not accept a more than a 10 year ROI.

[rscott]

Then someone has either fudged your #'s. Payback / ROI / Break-even under 10 years is unusual. You are expecting less than half that, so be prepared for a surprise

I went through EnergySage, and got 6 quotes, which came in at: 4.2, 4.5, 4.6, 4.6, 5.1, and 6.0 years.

The key is the high electric/SREC prices. I'm in Massachusetts, and my current "simplified" electric rate (total bill divided by kWh) is $.215. The calculations also include RECs (over $250 per MWh). Besides the Federal tax credit, there's also a state tax credit, but it is capped at $1,000.

[Mike90250]

Looks like you are all set, and enjoy the Energy Sage Koo Aid.. Rates are $.25 + in Calif, and nobody I know, looks at <5 years.

[rscott]

Looks like you are all set, and enjoy the Energy Sage Koo Aid.. Rates are $.25 + in Calif, and nobody I know, looks at <5 years.

I'm not sure what to make of this.

Are you saying that Energy Sage is doing something wrong (e.g. not calculating properly)? That their providers are providing exaggerated estimates of production? That Energy Sage is promoting solar in some unhealthy way (e.g. hyping the benefits without pointing out the drawbacks)?