wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Just my two cents, pls correct me if I'm wrong
- Thread starter WasGSOHM
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WasGSOHM
Senior Member
- Location
- Montgomery County MD
- Occupation
- EE
Wake me up at the summer solstice. . .in fact, wake me when it's over. . .
WasGSOHM
Senior Member
- Location
- Montgomery County MD
- Occupation
- EE
This one sticks with me.
Let's say a system with a Present Value of 60 kilobucks
on a tarpaper shack and
an Investment Horizon of X years.
The elec. generated is like an annuity to the shack owner.
Power grid or wind turbine elec. costs Y dollars per kWh and no panel maintenance costs.
What would have to be true for this to make sense anywhere on this planet?
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Um, no, you cannot confirm or deny PVwatts modeling of year round PV production (which is based on latitude and historical local weather data) simply by taking a couple of one time measurement. You can, however, go to https://pvwatts.nrel.gov/ and run the numbers yourself and confirm that Wayne is not lying to you.
The shack or lack thereof is irrelevant.
With 60K invested, pick your desired ROI.
10%, you must generate 6K of income.
Around here at retail, that’s > 40,000 kwh. I have no idea if that’s practical or not.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
It's simply a matter of the levelized cost of electricity (cost divided by expected kwh produced by the system over it's lifetime) as compared to what one will save or get paid for producing it.
In California or Hawaii it's usually a no brainer.
that’s 3,300 kWh per month.
More than a 4,000 sq ft house.
add demand and solar won’t keep up
I believe where it’s mounted at (shack or POC house) is very relevant.
The last thing you want to do is have these yahoos mount a solar system on a piece of crap house. With the cost of solar there is around a 10 year break even IF all goes well and you follow the right numbers.
Need a new roof in 10 years? It would be nice if the roof will last AT LEAST 20 years. And hopefully nothing happens to need early removal of these panels for maint. and repair.
I have tested (anti- islanding) new installs that were roof mounted and were close to needing a new roof when I was there.
And all the caulk these guys use on a roof install is insane. It won’t last...
My point was that the ROI calculation is the same regardless of what’s beneath the panels.
Of course, you’re correct...if what the panels are mounted on collapses or needs extensive repair, there’s a problem!
WasGSOHM
Senior Member
- Location
- Montgomery County MD
- Occupation
- EE
The extremes of the values tells you the range, and the published insolation values for your location tells you the average and what variation you can expect.
I don't think you'll have to dig this deep, though, to see through the puffery of salespeople. Not lies, but puffery, so say the courts
I doubt that anyone on this forum is lying.
If I post something that I believe to be true but isn't, it's a false statement. A lie is when someone posts something that he or she knows is false.
I studied up on BS and body language when I tried to blow the whistle on a corrupt federal agency.
This agency made The Sopranos seem like honest folks.
Every seven years or so these people get into the papers for some scandal but they scapegoat some employee and then things go back to normal.
The guy I remember that they pushed out had a doctorate and worked there 30 years, but he was not anglo-saxon. Or he might have just offended some higher-up.
The cops and others turn to Paul Ekman, who made videos of people who turned out later to be lying.
He found that micro expressions on a person's face that are gone in an instant provides clues to this.
IIRC, there was a woman who promised she was no longer suicidal. She lied. They went over that video countless times, looking for any hint.
I think he said there are 30 muscles in the face but 3000 different expressions.
It was probably a few years ago that I passed from skeptical to cynical.
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jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Whether the solar 'keeps up' with the facility. usually has little to do with its value proposition. Overproducing often runs into limits on what you get paid pack. Underproducing doesn't.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Why reinvent the wheel when PV Watts is more accurate and reliable and conservative enough to base an investment decision on? Just sayin.
It's a little unclear to me what exactly you're trying to say about salespeople, but here's my two cents:
First, putting solar panels flush to the north side of a house may or may not be cost-effective in any given situation. It should not be dismissed out of hand as snake oil salesmanship. I've seen some northside installs that I definitely thought were suspect. I've also installed panels for people on north (more often northeast or northwest) facing roofs when it was plenty cost-effective for them. We've also tilted them back to the south plenty of times, but sometimes aesthetic or cost reasons (engineering) make that not the best choice. Every project deserves its own consideration of the factors involved.
Second, there are surely some dishonest or unknowledgable salespeople in the solar industry, as there are in any industry. But I hope your comments are not intended to refer to the whole industry, which also has plenty of honest and well meaning people and companies.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Maybe they focused them on a reflection from the neighbor to the north of them
To the response from retired,
I’m saying that a $60,000 unit to have to put out 3,333 kWh per month per his figures, will not happen.
I have on file here a $60,000 install that is only 15.2 kW.
It’s not going to keep up with the required energy demands to produce 3,333 kWh per month the way people live normally.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
(I still don't know why it matters, but...)
Actually it's within the realm of possibility, and is certainly the right order of magnitude. For example if a $60k system produced 1.9kwh per watt per year and it cost about $2.80/watt to install it could meet that goal. These are very good numbers for residential but they do happen in the real world. And at more average numbers of something like 1.5kwh/W/yr and $3.50/W the system is still providing two thirds of that.
Btw 3,333kwh to 'live normally' is very relative. Me and my family use about 160kwh a month.
Your kinda missing the gist of the entire conversation from my point...
go to post 26, that’s where the figures come from..
10% per year return was quoted as >40,000kWh By retirede.
I broke it down to monthly kWh. That’s 3,333 kWh. If you got a house that uses that much energy, a 15 kW system isn’t going to keep up to give you a good ROI.
by “normal“ I’m talking about the demand on a house that has a 3,333 kWh bill monthly.
if your using 3,333 kWh monthly, your demand is going to be in the 28-35 kW range.
I only use about 25-3100 in the summer In a 4000 sq ft house.
And I’m not saying all installers are yahoo’s. I’ve met some very good ones that are very knowledgeable and help the HO
ran out of time...
personally I respect your opinion on installs and figures, so no animosity in my postings here.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
- Occupation
- Electrician
A couple points ( some already mentioned by JB):
1. I doubt there are more sleazy lying sales people in solar than any other industry.
2. Off south panels may be fine from a payback/production standpoint. You really can't generalize here
3. Newflash: People do PV for different reasons. Maybe it's not about money/payback? How many Americans have a big dumb $60,000 truck that they don't need, no one ever says anything about that. I just spent $12,000 on 500 sq feet of tile and have a $5,000 bathtub, but I'm still pooping in an outhouse (sometimes on a piece of cardboard if I don't want to trudge thru the snow at 6:00 AM - yes in the winter in the Northeast. Screw you mind your own business I'll spend my money on whatever I want thank you very much.
1. I doubt there are more sleazy lying sales people in solar than any other industry.
2. Off south panels may be fine from a payback/production standpoint. You really can't generalize here
3. Newflash: People do PV for different reasons. Maybe it's not about money/payback? How many Americans have a big dumb $60,000 truck that they don't need, no one ever says anything about that. I just spent $12,000 on 500 sq feet of tile and have a $5,000 bathtub, but I'm still pooping in an outhouse (sometimes on a piece of cardboard if I don't want to trudge thru the snow at 6:00 AM - yes in the winter in the Northeast. Screw you mind your own business I'll spend my money on whatever I want thank you very much.
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