High capacity grid tie single phase inverter

[TAZ427]

I appreciate your support Taz. I have only ever lived in Oncor territory so do not know what it is like to spend 24 cents per kWh but if I can get a 4-5 year payback on solar vs 10 cents a kWh it seems like a no brainer to me...

Well at $0.10/kWh w/ targeting ~22,000kWh/yr roughly that's $2200/yr * 5 yrs, that's a $11,000/0.70 -> $15,714 pre-tax credit budget. If you're at ~15KW System to get ~22,000kWh/yr (Assuming used PVWatts for analysis - if not do so) that seems a very aggressive budget at ~$1/W before tax credit. I'd be interested in hearing what some of the DIY crowd say on that.

I'd do the homework for everything you're going to need down to the tiniest details as a lot of the 'little stuff' can start adding up quickly. But before I'd go to that effort, I'd verify that someone is going to provide you with Net Metering, and have specifics in writing as to what exactly the service agreement calls for in terms of what you pay per kWh delivered to you and what they credit you with per kWh that you deliver to them, and if credits are maintained from month to month, until an annual true-up, ... If you don't have all that in writing some place, you're doing this in blind faith, and you could have a system were you effectively consume < 1/2 of the energy it produces a year, more than doubling your ROI timeframe.

[J.P.M.]

Actually I wondered if your pen name was Rik DeGunther? The bulletins still come here, and
even in my electronics specialty, one design problem after another that we struggled with
decades ago has been reduced to "cookbook" solutions. The little corner of electronics I
claim to know something about, keeps becoming a smaller and smaller part of the whole.
so be it, Bruce Roe

Being slow on the draw, I just figured out why you might think I'm someone else.

I suggest the "Dummies" book a fair amount because it seems a good primer for those in need of information. I don't agree with all of it, but that matters not. It's mostly good info that's mostly complete, with info where to get more info. And no, I've never met Rik DeGunther (yet), nor do I get a spiff by mentioning his work. I'm a whore like everyone else when it come to making a buck, but I'd like to think my price is a lot higher than that.

I appreciate and share your little corner comment. Mine's probably smaller than yours and getting more irrelevant as f(time) to those younger than me (or maybe with just more of their brains left). Such is reality.

BTW: You are not the first to think I was someone else. Seems like a lot of my former coworkers thought I was some ancient Greek king named Oedipus. I could tell that by how they often referred to me.

Respectfully,

[Fourthbean]

I appreciate your support Taz. I have only ever lived in Oncor territory so do not know what it is like to spend 24 cents per kWh but if I can get a 4-5 year payback on solar vs 10 cents a kWh it seems like a no brainer to me...

[TAZ427]

Has anyone noticed he lives in TX, not in Austin because he is on Oncor where there is no Net Metering Laws, offering such great deals? Anyone find that strange? Going residential rates are less than 10-cents per Kwh, and I have never heard of any utility in TX allowing unlimited over production with banking of 12 months.

I wish I knew, everytime I did the simple math it was a no-brainer that Solar wasn't the way to go. Never even got to metering considerations. Last time I looked while living in TX was 3yrs ago, it wasn't feasible for me but I was looking at pro-install pricing too. FWIW, I lived in Houston area from '96-'15

One thing that throughs an interesting wrench in the works is the 'Power to choose' laws. Which always anybody to make a company, negotiate rates w/ the PoCo, and then sell power, making them the retail provider, while the PoCo is still the service provider. There are literally dozens of retailers in the Houston area, while Reliant Energy (NRG now I believe) is the service provider. I did this for the last 10yrs or so living in Texas (since the went into effect) as Reliant Energy jumped their rates to ridiculous numbers for Houston (they had the right to set their Residential rates to whatever they wanted at that point) and everybody said screw it, I'm going with Company XYZ for $0.10-0.12/kWh like what I was paying before.

Anyway, while Net Metering isn't required by the PUC of Texas - the dual metering is required to be provided if requested, and anyone can become an Electric PoCo and generate and sell (lots of Wind Power in NW parts of Texas. Looks like more recently the big PoCo's are more agreeable to Residential Solar as well. At least I found some things with Oncor and 1kW-15kW DC Residential Solar programs. I'd assume you still need to have a working agreement w/ a Retailer Provider for the Net Metering aspect, but I'd be surprised if it can't be done.

That said, is it financially feasible? I'd say no if you're paying the $3/W pro-install. But probably if you're DIY. Of course, one needs to crunch the numbers.

[J.P.M.]

Has anyone noticed he lives in TX, not in Austin because he is on Oncor where there is no Net Metering Laws, offering such great deals? Anyone find that strange? Going residential rates are less than 10-cents per Kwh, and I have never heard of any utility in TX allowing unlimited over production with banking of 12 months.

yea, notice 3d para., my 07/10, 2136 hrs. post.

Being in TX, I figured the cost/kWh was relatively low, but too lazy to root around in rate schedules. Figured I'd let you or some other knowledgeable Texan inform the OP of questionable cost effectiveness possibilities.

[Sunking]

Thankfully here in Oncor territory it is regulated by the Public Utility Commission of Texas. The customer is looked out for pretty well in that sense. So one of the plans I looked at allowed me to store KWh in the grid for when I need it later

Has anyone noticed he lives in TX, not in Austin because he is on Oncor where there is no Net Metering Laws, offering such great deals? Anyone find that strange? Going residential rates are less than 10-cents per Kwh, and I have never heard of any utility in TX allowing unlimited over production with banking of 12 months.

[J.P.M.]

Actually I wondered if your pen name was Rik DeGunther? The bulletins still come here, and
even in my electronics specialty, one design problem after another that we struggled with
decades ago has been reduced to "cookbook" solutions. The little corner of electronics I
claim to know something about, keeps becoming a smaller and smaller part of the whole.
so be it, Bruce Roe

Bruce: I'll kill that speculation now. No. That ain't me.

Other than some blurbs in my HOA's news letter about how homeowners can decrease the probability of getting a mostly self induced screwing by doing PV while being solar ignorant, the only thing I ever did that was close to being "published" has been languishing in my Alma Mater's library since ~ 1988 or so and deals with methods of changing (with the usual goal of increasing) the onset frequency of flow induced vibration of tubing in shell & tube heat exchangers as f(tube axial stress) and the variation of some other mechanical design parameters in what are perhaps some unusual ways. It mostly dealt with the kind of stuff that caused the San Onofre boiler refits to fail prematurely.

IMO only, they should have seen that one coming in the early stages of the design of the refit. Looking at it from the outside, seems to me that MBA's and mgmt. made bad choices, and some spineless engineers let them get away with it, but that's way off topic.

[bcroe]

Hey Bruce: Send me your hat. Seems the more I learn, the more I find out I don't know. Result: I realize how much I know as a % of all knowledge gets smaller all the time. Result: Using the criteria that I know less than thought, I get continuously dumber. The goal at this stage is to die a complete nitwit (a goal my bride - and most likely some readers of my mental spoor - claim I achieved long ago).

BTW, I attended the conference that was the basis of the "Home Remedies" book, met Tom Wilson and contributed a couple of ideas on calcing' building heat loads. I also had him sign my copy of the book after its publication in 1981. Don't know if the original was ever updated. I kind of doubt it. Even so, or if not, still many nuggets of wisdom and a lot of common sense in there, even if some of it has become dated and perhaps a bit anachronistic.

Regards,

Actually I wondered if your pen name was Rik DeGunther? The bulletins still come here, and
even in my electronics specialty, one design problem after another that we struggled with
decades ago has been reduced to "cookbook" solutions. The little corner of electronics I
claim to know something about, keeps becoming a smaller and smaller part of the whole.
so be it, Bruce Roe

[J.P.M.]

Or get a nice used paperbound copy of that and also SOLAR POWER YOUR HOME FOR DUMMIES
also by Rik DeGunther, and HOME REMEDIES Tom Wilson all for hardly more than media postage
for 4 lb from 61084. While these are a good beginning, they don't extend to my operation of an
overwhelming supply of solar energy to cancel all home consumption. I would like to turn in my DUMMY
cap. Bruce Roe

Hey Bruce: Send me your hat. Seems the more I learn, the more I find out I don't know. Result: I realize how much I know as a % of all knowledge gets smaller all the time. Result: Using the criteria that I know less than thought, I get continuously dumber. The goal at this stage is to die a complete nitwit (a goal my bride - and most likely some readers of my mental spoor - claim I achieved long ago).

BTW, I attended the conference that was the basis of the "Home Remedies" book, met Tom Wilson and contributed a couple of ideas on calcing' building heat loads. I also had him sign my copy of the book after its publication in 1981. Don't know if the original was ever updated. I kind of doubt it. Even so, or if not, still many nuggets of wisdom and a lot of common sense in there, even if some of it has become dated and perhaps a bit anachronistic.

Regards,

[bcroe]

Buy a book: " Solar Power Your Home for Dummies". You need more basic information. 20 bucks well spent.

Or get a nice used paperbound copy of that and also SOLAR POWER YOUR HOME FOR DUMMIES
also by Rik DeGunther, and HOME REMEDIES Tom Wilson all for hardly more than media postage
for 4 lb from 61084. While these are a good beginning, they don't extend to my operation of an
overwhelming supply of solar energy to cancel all home consumption. I would like to turn in my DUMMY
cap. Bruce Roe

[peakbagger]

IMHO go with a couple of smaller inverters and shoot for a model with two or more independent MPPT circuits. That way you end up with 4 independent MPTTs in case you have a shading issue with part of the array the other 3/4s keep chugging along unless they too are affected. Also if you smoke an inverter you still have 50% capacity while you replace the smoked one. Its also nice to be able to compare the two to each other for troubleshooting.

[J.P.M.]

TAZ427, I appreciate the insight that the 14% number is conservative. I will dial it up to 10% as you suggest for my calculations.

As mentioned I should have a handle on cooling/heating costs with the months I have been here. I have likely gotten ahead of myself as my panel price is low enough I am considering "throwing panels at my utility bill" as it seems easier than air sealing, blowing insulation, replacing windows, sealing 16x8 holes in our floors, you know - the basic stuff . Looks like my panel cost is going to be about the same as my inverter cost.


J.P.M, I cannot stand peddlers. Can't trust a word they say . Do you know if that book is something I could digest in audio format or should I get a text version? Some times there is a lot of reference material that is hard to understand in audio format.

Thankfully here in Oncor territory it is regulated by the Public Utility Commission of Texas. The customer is looked out for pretty well in that sense. So one of the plans I looked at allowed me to store KWh in the grid for when I need it later.


foo1bar, I forgot Solaredge did the power optimizer deal. Sure hits my per panel price when I have to throw one of those on each. And good point with my 72 cell panels being higher voltage than most residential systems. I'll check out the other options you presented, appreciate it! I hadn't found Fronius in any of my previous searching.

On the book: 20 bucks softcover. Don't know about other formats, but for the amt. of reference data, tables etc. contained, it doesn't seem to lend itself to an audio format. Good, basic stuff.

I think I understand about peddlers. Few who claim sales job titles are little more than order takers and clerks. I spent 10 yrs. as a sales rep/slug. Got bored and sick/tired of explaining simple principles to people claiming to be engineers, so I went back to school and became one (an engineer, that is). Took a pay cut to do it, but not bored afterward.

As for living in an energy sieve, suit yourself. Just sayin' it's cheaper and probably more comfortable to not use energy through conservation than to produce more of it, particularly where electricity costs are relatively low as in most of TX, and particularly now that net metering will be winding down. You'll understand why as you get more informed.

Good luck.

[Fourthbean]

TAZ427, I appreciate the insight that the 14% number is conservative. I will dial it up to 10% as you suggest for my calculations.

As mentioned I should have a handle on cooling/heating costs with the months I have been here. I have likely gotten ahead of myself as my panel price is low enough I am considering "throwing panels at my utility bill" as it seems easier than air sealing, blowing insulation, replacing windows, sealing 16x8 holes in our floors, you know - the basic stuff . Looks like my panel cost is going to be about the same as my inverter cost.


J.P.M, I cannot stand peddlers. Can't trust a word they say . Do you know if that book is something I could digest in audio format or should I get a text version? Some times there is a lot of reference material that is hard to understand in audio format.

Thankfully here in Oncor territory it is regulated by the Public Utility Commission of Texas. The customer is looked out for pretty well in that sense. So one of the plans I looked at allowed me to store KWh in the grid for when I need it later.


foo1bar, I forgot Solaredge did the power optimizer deal. Sure hits my per panel price when I have to throw one of those on each. And good point with my 72 cell panels being higher voltage than most residential systems. I'll check out the other options you presented, appreciate it! I hadn't found Fronius in any of my previous searching.

[foo1bar]

I found a supply of panels that were excess from a solar power plant. I want to do somewhere in the 14kw range for our house. However I noticed single phase inverters seem to top out around 8kw. Anyone know why? Should I plan to use two inverters?

Thank you littleharbor, could NOT for the life of me figure out why I was being truncated.

Side note: I could not resist buying more panels that I need, so If you are in the ft worth tx area and want some 310-325w Jinko panels for $145 let me know.

325W Jinko panels are probably 72-cell - make sure you are properly accounting for the voltage on them.

There are plenty of 10kW+ inverters.
Fronius has a 15kW inverter.
Solaredge has a 11.4kW - and you also have possible choice of doing multiple inverters (ex. a 7.6kW and a 5kW or a pair of 7.6kW)

Many places have simpler rules for 10kW and smaller installations - so you probably want to look into that. (And there are rules for the permit dept (AHJ) and for the POCO - so make sure you understand both before you buy more stuff.

And I'd definitely want to iron out the details on how the POCO billing will work.
I'd be surprised if you can bank kwh for over a year. I'm not saying it's impossible - just that such a thing would be unusual.
The typical (or typical for favorable-to-solar ) is that the kwh and $ billing is settled up once a year on the anniversary of the system being online (from POCO's perspective)
Sometimes the kwh are paid out at $0/kwh - sometimes at a small amount per kwh (like what the POCO pays for power, which may be like $.04/kwh
Every POCO is different though - so make sure you understand *your* POCO's rules.


BTW - if you do solaredge system make sure the optimizers are right for your panels - most people have 60-cell panels, and I *think* yours are 72-cell, which probably means a different optimizer.

[J.P.M.]

So many quick and helpful replies, thank you!

I do have 320A service, but I can see why no one would sell an inverter for that since most are 200A max.

Yes by single phase I meant 240v as you described.

I amable to feed back to the grid any power I do not use, then choose my retail provider on how that is handled. Should be able to find one where I can pull the energy back in kw for kw. Pretty sweet deal, batter bank I do not have to maintain! I did not see any regulation on how much I could feed back in, just that I would lose any extra after a year.

I do not have a good baseline for power as we moved here in December. Last month we were cooling half the house and used over 1500kwh.

According to pvwatts with a 14% loss rate I get about 21k kWh a year. Right now I think it will be about right for our 4600sqft house. I do have plans for being more efficient in the future however so it could be overkill in the future.

Buy a book: " Solar Power Your Home for Dummies". You need more basic information. 20 bucks well spent.

As mentioned, doubling a Dec. - June usage may be a decent 1st approx. for annual usage. But know that conservation and use reduction before PV will pay back 2X - once in bill reduction that's more cost effective than throwing PV at a high electric bill, and 2d, when the PV system can be smaller (less $$) as a result of the smaller, conservation reduced electric usage.

Getting PV before conservation and use reduction is doing it exactly backwards.

Get familiar with the net metering options and rules your POCO (POwer COmpany) offers, and be aware that such options are probably changing and probably becoming less favorable than in the past. Don't believe much of what you read and hear from the peddlers and the media, or do so at your own risk. This is probably the biggest PITA of the whole exercise, but necessary if you expect any hope of a cost effective system.

Use 10 % system losses as suggested, get your own estimates of system output, and don't pay much attention to low production estimates from peddlers who make money putting product on your property, not putting cost effective systems in place or saving you money. No peddler ever got fired for oversizing systems.