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SwedishRider
Rider on the Storm
Premium
join:2006-01-11
not Sweden
kudos:1
reply to HarryH3

Re: [Green Tech] Solar panels: doing the math...

said by HarryH3:

Seems to me that you're creating a system that is far too large for your needs. Even if you could generate the total of your daily average in just 4.2 hours, how would you store it for use during the other 19.8 hours of the day? Utilities are quickly realizing that they need to back away from paying above-market rates for backfeed from solar arrays. So don't count on selling your excess to them and then getting it back free or cheap.

I thought the power meter spins backwards when more power is being generated than consumed, thus putting power into the grid and offsetting the power drawn in the overnight hours when no sun is present. That was my understanding of a grid-tied system with no batteries, but please correct me if I am wrong.

How do the numbers work out if you just install a system that will cover your power needs during daylight hours?

Tough to know what is needed just to cover day hours. I could go with a smaller system to help supplement with power consumption, but I'd still be subject to utility prices for a portion of my bill. What might a reasonable, smaller size system be?

robbin
Premium,MVM
join:2000-09-21
Leander, TX
kudos:1
Meter doesn't spin backwards. You get a special meter that meters in both directions. They don't necessarily buy excess for the same price as they sell it to you. All utilities are different on what they pay and how they do it with credits, etc.


SwedishRider
Rider on the Storm
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said by robbin:

Meter doesn't spin backwards.

I saw in a few YouTube videos that the meter spun backwards once the panels were connected. Must have just been that particular meter type then.


Solar power

@mycingular.net
reply to SwedishRider
You will need a net metering agreement with your POCO before backfeeding into the grid. Most modern electromechanical meters are interlocked mechanically so they won't run backwards. Most electronic meters without net metering programming enabled record all energy passing through the meter as energy delivered to the consumer. The terms of net metering agreements are getting less favorable with each passing day so it would be wise to check with your POCO before formulating any pay-back estimations. The actual contract terms can have a very major effect on your eventual payback.


SwedishRider
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reply to robbin
Jump to 8:40 for the spinning backwards part.

»www.youtube.com/watch?v=JHCrdtIvD3I

HarryH3
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reply to SwedishRider
Most utilities won't do a 1-for-1 "swap" on the excess power. You get a different meter when you grid-tie and that meter tracks kWh in and out. You pay more for the "in" than they pay you for the "out". I read at article the other day that said that wholesale generation costs an average of 6 cents per kWh. Utilities will not be standing in line to pay more than that for solar generation at the residential level.

Since a/c isn't a large part of the electric bill in CT, then it becomes harder to work out the numbers for what size works best. Even here in TX, with dual 3.5-ton a/c units, they only add around $125-150 per month to our bill during the hottest summer months.

The largest problem with solar and wind is what to do with the excess. There just isn't much in the way of economically feasible energy storage to save the excess until it's needed. There was recently a thread here about how Hawaii has placed a moratorium on grid-tie systems because their grid can't handle all the extra power being backfed to it.


SwedishRider
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said by HarryH3:

Most utilities won't do a 1-for-1 "swap" on the excess power. You get a different meter when you grid-tie and that meter tracks kWh in and out. You pay more for the "in" than they pay you for the "out". I read at article the other day that said that wholesale generation costs an average of 6 cents per kWh. Utilities will not be standing in line to pay more than that for solar generation at the residential level.

Then that being the case, a system sized that big would not essentially replace my whole-house needs.

What's the sweet spot then? Is there a size that makes sense given my situation? My overnight draw is low, and the only thing that might change that would be if I bought an electric or plug-in hybrid car.

robbin
Premium,MVM
join:2000-09-21
Leander, TX
kudos:1
First thing you need to research is what your supplier pays for excess solar power.


SwedishRider
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said by robbin:

First thing you need to research is what your supplier pays for excess solar power.

I just read in a few places CL&P will pay $0.055 to the customer for excess solar energy. That may change, but that seems to be the rate for now.

Zach1
Premium
join:2006-11-26
NW Minnesota

1 edit

1 recommendation

Given your calculation of $0.16/kwh for purchased power and your utility only paying $0.055/kwh for your excess power, the payback will come mostly from power you generate that prevents imports from your utility. Without knowing more, I would size the system to cover your Summer baseline load during daylight hours. If TOU options exist in your area that would allow you to receive a higher rate for power you export during peak hours, a larger system may be more cost effective. Especially if you are able to, not only cover most of your on-peak usage, but also export enough during peak hours to cover a good portion of the cost of your off-peak usage. Up here in the northern states, solar is sort of a gamble as to whether or not the payback is reasonable.

Just for the record, I have 36 kw of wind generation capacity and I'm "lucky" enough to live in an area with consistent wind energy. On the local co-op, the rate I'm paid for my exports is $.062/kwh and imports are billed at $.091/kwh. Local generation has reduced my kw demand charges slightly so there is some minor savings there. Before someone has a chance to chime in about the cost of my green energy being partially shouldered by tax payers; I didn't take any tax breaks or write offs. Over the last two years, the turbines averaged a tad over 3800 kwh/month although January 2014 was a new record at 9413 kwh. Annually, the system output covers ~60% of our domestic/farm/business electrical usage. This doesn't include the irrigation meters. As for ROI, if I'm lucky, I may recover the cost before I die. When all was said and done, I had more in this little project than I care to add up so I quit adding when the calculator stopped displaying numbers and just said HOLY $HIT.
--
Zach


edit: typo

ke4pym
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Charlotte, NC
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reply to Solar power
said by Solar power :

Most modern electromechanical meters are interlocked mechanically so they won't run backwards.

Heh, the modern spinny meter I had on my house most certainly spun backwards when I fired up my array for the first time.

ke4pym
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Charlotte, NC
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reply to SwedishRider
said by SwedishRider:

said by HarryH3:

Most utilities won't do a 1-for-1 "swap" on the excess power. You get a different meter when you grid-tie and that meter tracks kWh in and out. You pay more for the "in" than they pay you for the "out". I read at article the other day that said that wholesale generation costs an average of 6 cents per kWh. Utilities will not be standing in line to pay more than that for solar generation at the residential level.

Then that being the case, a system sized that big would not essentially replace my whole-house needs.

What's the sweet spot then? Is there a size that makes sense given my situation? My overnight draw is low, and the only thing that might change that would be if I bought an electric or plug-in hybrid car.

You really need to contact some quality installers in your area to help you go over the specifics. They will come out and do a site survey and provide you with a lot better information than any of us here can.

My utility currently does a 1:1 swap. Though, they're trying to weasel out of their commitment. I don't see how an electron I put on the line is worth any more or less than what they put on the line.

The other argument I hear a lot is "solar producers don't pay their fair share". Which I think is hog wash. How is it any different than simply reducing one's consumption?

But the utilities are terrified of this new disruptive technology. While I will concede that the grid was never designed for this, the utilities are going out of their way to cram the genie back in the bottle (perhaps a little earlier than the RIAA did with Napster).

ke4pym
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reply to Zach1
said by Zach1:

Before someone has a chance to chime in about the cost of my green energy being partially shouldered by tax payers; I didn't take any tax breaks or write offs.

The one thing the folks making this argument forget is the big utilities are getting much bigger tax breaks than all of us combined.

You should have taken them.


Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1

1 edit
NM. My comment was off topic to an off topic post.

ke4pym
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said by Jack_in_VA:

I'm sure you can provide documentation to substantiate that claim. Utilities don't need tax breaks as they pass on real costs to customers and are regulated.

Really? Ok. I'll start at home.

»www.ncpolicywatch.com/2013/04/10···-energy/

From 2008-2012 Duke's tax rate was -3.3% or nearly $300 million in rebates.

That's quite a bit more than I'm getting back.


SwedishRider
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reply to ke4pym
said by ke4pym:

You really need to contact some quality installers in your area to help you go over the specifics. They will come out and do a site survey and provide you with a lot better information than any of us here can.

Fair enough. I'd need to see how they have these systems priced, and how much the savings would be to see if it would be worth it. And I still have unanswered questions, such as: How expensive is it to remove and reinstall the panels in the event of a new roof installation? What is the cost to dispose of panels that have no more useful life? And who fixes these panels in the event of a problem (and how many are qualified to fix them)? I'm still not sold on this concept, but the idea is interesting.


Jack_in_VA
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North, VA
kudos:1

1 edit
reply to ke4pym
NM

ke4pym
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reply to SwedishRider
said by SwedishRider:

Fair enough. I'd need to see how they have these systems priced, and how much the savings would be to see if it would be worth it. And I still have unanswered questions, such as: How expensive is it to remove and reinstall the panels in the event of a new roof installation? What is the cost to dispose of panels that have no more useful life? And who fixes these panels in the event of a problem (and how many are qualified to fix them)? I'm still not sold on this concept, but the idea is interesting.

Again, the local installers will be able to help you with that. Personally, I had my roof redone a month prior to the panels being installed. Since the sun no longer shines on that side of the roof, it should be a non-issue.

However, should you need to have the array taken down, you're going to be charged for then market rates.

The installers should be on the hook (should they be in business) if anything fails.

My panels have a 25 year output warranty on them. Ditto for the inverters and 10 years of warranty on the install. But, like anything else, stuff changes. So if something breaks you'll have to fix it if the installing company goes belly up. If I'm still alive and in this house in 25 years, I'll be looking to put the new fancy high-tech stuff up on the roof to get another 25 years of service.

The last thing I think will be a problem is the roof leaking. They installed some bang up hardware and there's not going to be any leaks. Search my post history if you want to see more on my install.


SwedishRider
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reply to ke4pym
Had a site survey done today. Installer is running the numbers now based on specifics of the site. I'll post when I have the specifics in hand.


Jack_in_VA
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North, VA
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Reviews:
·Millenicom
said by SwedishRider:

Had a site survey done today. Installer is running the numbers now based on specifics of the site. I'll post when I have the specifics in hand.

He should have been able to do that in a few minutes. With technology today laptops and Ipads loaded with the appropriate software it's just plug in the numbers he determines in the field. (your site)


SwedishRider
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Not everyone carries a laptop or iPad with them. I don't need instant gratification, and sometimes I prefer old school paper and pencil. I wouldn't look down at a contractor or an installer who wants to take a little time to put together their information.


Jack_in_VA
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North, VA
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Reviews:
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That's fine. I just guess that some companies are more technology advanced.

When I was looking to replace my heat-pump the rep came out we sat at the table and went over the various models and specifications. He plugged the numbers printed out the quotes for 3 systems for me and my wife to consider. Said to consider them and give him a call.


SwedishRider
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1 edit
He did give me literature on some of the components he uses. He would use Sunpower E20-327 panels: »us.sunpower.com/homes/products-s···-series/

And he uses these Power One inverters: »www.power-one.com/renewable-ener···a/series
I've read these are quality components. Can anyone here confirm or comment?

ke4pym
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join:2004-07-24
Charlotte, NC
Reviews:
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said by SwedishRider:

He did give me literature on some of the components he uses. He would use Sunpower E20-327 panels: »us.sunpower.com/homes/products-s···-series/

And he uses these Power One inverters: »www.power-one.com/renewable-ener···a/series
I've read these are quality components. Can anyone here confirm or comment?

Research, research, research. If you want I'll be happy to ask my installer what they think of them.

You'll be going with string inverters. With that you'll want to make that all the panels will have direct exposure to the sun.

With string inverters if one panel has a power drop all of the other panels on that string will drop to match.

My installer gave me very, very rough numbers prior to his site visit based on information gleened from Google maps. He gave me rough numbers after his initial site visit and about 3 or 4 days after I had a full proposal mailed to me. We then tweaked it here and there to match my desires, location issues and budget.

What are the various warranties like?


SwedishRider
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1 edit
said by ke4pym:

What are the various warranties like?

Installation warranted for 5 years (workmanship, leaks, etc) excluding acts of God.
Inverter warranted for 10 years.
Panels warranted for 25 years.

He said something about those inverters needing a card change of some kind rather than a full inverter replacement if it fails, costing hundreds instead of thousands when the inverter goes. That's how I understood his explanation of that unit.

If you could ask your installer, that would be great. Thank you!

EDIT: And yes, the panels would be in full, unobstructed view of the sun for the vast majority of the day(very early morning and very late evening might see a little shade), so string inverter setup not an issue.


Corehhi

join:2002-01-28
Bluffton, SC
Reviews:
·Hargray Cable
I got quotes for installing a solar array and one company was going to gladly sell me a $1500 inverter repair policy and another told me the truth. The second guy said the inverter will fail in about 10 years but it's a matter of sending it back to the company to be rebuilt which at that time was about $265. What part(s) they needed to replace I do know. Both companies used Sunny Boy inverters BTW.

foo11223344

join:2004-01-09
Tarrytown, NY
reply to SwedishRider
said by SwedishRider:

Installation warranted for 5 years (workmanship, leaks, etc) excluding acts of God.

So if an Act of God occurs and damages or perhaps destoys the panels, would the panels and other equipment on the roof be covered by standard homeowners insurance? Or do you need a separate rider for solar installations? One bad storm that takes out several panels could easily turn your ~9 year payback into much longer.

ke4pym
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Charlotte, NC
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said by foo11223344:

said by SwedishRider:

Installation warranted for 5 years (workmanship, leaks, etc) excluding acts of God.

So if an Act of God occurs and damages or perhaps destoys the panels, would the panels and other equipment on the roof be covered by standard homeowners insurance? Or do you need a separate rider for solar installations? One bad storm that takes out several panels could easily turn your ~9 year payback into much longer.

You should consult your insurance agent.