How to Calcluate Requirement

[J.P.M.]

Okay so after doing more research (my homework from these posts) I have figured out that if I want to 100% offset and my current yearly usage is 15,590 and I want a 15% increase PLUS add for future pool equipment (estimated at 325 per month) then I need 17,928 plus 3900 for pool = 21,828 per year. Which converts to a 10,870 KW system. That will produce 17,893 kWh per year (at 82% usage). If my price is 60k for example, do I divide by the KWH per year or the KW system size to get the per kilowatt price?

I believe you need more homework. The common way of defining the price per Watt paid for a system is the total price paid before any credits/rebates/kickbacks by the system size in Watts. So, $60,000/10,870 = $5.52/Watt. I hope that $60K is some number you made up as that would be an exorbitant amount to pay for a system that size. Also, I kind of doubt you'll get 21,828 kWh/yr. from a 10.87 kW system.

FYI, system size is in Watts or kiloWatts (1,000 Watts). Those are units of power. System output is in kilowatt-hrs., usually per hr, day , month, year or some time period. Those are units of energy.

As I suggested, "Solar Power Your Home for Dmmies" is one good, cheap (like free) and readily available source of information as well as PVWatts after you get a handle on what you're trying to figure out. Learn to crawl before you try to walk.

BTW, suit youyrself, but if you are after the most cost effective system for the long term, usually and often, a 100% offset of an electric bill is not the way to go. More homework.

[Anjen]

hope that $60K is some number you made up as that would be an exorbitant amount to pay for a system that size. Also

The price I was given was for 34LG 315 watt panels to produce a 10,710 watt system. It was estimated to produce 17,400 KWh per year. This would use Enphase Micro inverters on three different locations (one South, Two West) - also includes roofing material (comp) installed under the panels.

$52,950

So based upon the above I figure this to be 52,590 / 10,710 = 4.91 per watt. Which seems very high to me. Getting bids I am not seeing how anybody has gotten prices in Orange County close to 3.50. The prices I have received (using the above math) are all above 4.25 per watt. Could it be that the calculation needs to be derived from the kwhours ???

[solar pete]

I am confused, are you getting major roof work done as well?

[J.P.M.]

The price I was given was for 34LG 315 watt panels to produce a 10,710 watt system. It was estimated to produce 17,400 KWh per year. This would use Enphase Micro inverters on three different locations (one South, Two West) - also includes roofing material (comp) installed under the panels.

$52,950

So based upon the above I figure this to be 52,590 / 10,710 = 4.91 per watt. Which seems very high to me. Getting bids I am not seeing how anybody has gotten prices in Orange County close to 3.50. The prices I have received (using the above math) are all above 4.25 per watt. Could it be that the calculation needs to be derived from the kwhours ???

Have the vendor(s) separate the cost of the PV system from any other work. Not doing so only muddies the water. There may also be some question about what is eligible for the fed. or other tax credits.
More BTW, $3.50/Watt is certainly possible in the OC as various posters have stated in prior threads. Educate yourself, know what you're talking about and vendors will not take you to the cleaners as badly once they realize you are not solar ignorant. Knowledge is power. Get some of the first.

[DanKegel]

The price I was given was for 34LG 315 watt panels to produce a 10,710 watt system. It was estimated to produce 17,400 KWh per year. This would use Enphase Micro inverters on three different locations (one South, Two West) - also includes roofing material (comp) installed under the panels.
$52,950

I paid $3.50/watt for 29 LG310 panels (well, 25 LG310's and 4 GxB300's, long story) on two different locations (south and west), and a solaredge 7600 inverter. 8.9 kW total.
There was roofing work, too, but I'm not including that cost.
The installer I used was http://www.solarreviews.com/installe...group-reviews/

They claim to cover part of OC.

[Anjen]

No major roof work, I am doing a remodel and the company offered to do the comp roofing under the solar. I have to have somebody do it anyway, but I can extrapolate that information to get a true cost. Seems he (and my other quotes) are too far off, I am going to have to keep looking. Can somebody please share some companies they have had luck with in OC.

[MikeInRialto]

Anjen, if you are going to be adding a pool/pool equipment - that is a whole other area of homework to be done. I have a friend who used to be a pool builder that due to a costly divorce lost his business and moved out if state. I have a pool and my friend shared some great ideas for my future pool renovation: plumbing, heating, surfacing. I don't know any pool builders out here, but can tell you what questions to ask & what things you might want for your pool, can also share my solar experience as well.

Admin Note, I removed your phone number its not allowed, cheers.

[Anjen]

MikeinRialto, that would be great can you PM me your info?

[Anjen]

Okay so after "much" further research and some suggestions from members, I have narrowed down to what I believe the two best quotes (from the same person who happened to be recommended by the forum members, I didn't post his name because I am not sure we are allowed to do that??).

#1 DCKW Size 12.18 to produce 20,000 kWh per year 42 Solar World 290 panels with Enphase Inverters for $36,500 which by my math equals 3.00 per DCkw (before incentives)
#2 DCKW Size 12.20 to produce 20,000 kWh per year 38 LG 320 panels with Enphase Inverters for 37,400 which by my math equals 3.06 per DCkw (before incentives)

3 separate roof locations.

Any suggestions on which is the way to go and any comments on my mathematical calculations to get my price per comparison? The other quotes are coming in at 4.07 and higher, so I won't waste everybody's time.

[J.P.M.]

Okay so after "much" further research and some suggestions from members, I have narrowed down to what I believe the two best quotes (from the same person who happened to be recommended by the forum members, I didn't post his name because I am not sure we are allowed to do that??).

#1 DCKW Size 12.18 to produce 20,000 kWh per year 42 Solar World 290 panels with Enphase Inverters for $36,500 which by my math equals 3.00 per DCkw (before incentives)
#2 DCKW Size 12.20 to produce 20,000 kWh per year 38 LG 320 panels with Enphase Inverters for 37,400 which by my math equals 3.06 per DCkw (before incentives)

3 separate roof locations.

Any suggestions on which is the way to go and any comments on my mathematical calculations to get my price per comparison? The other quotes are coming in at 4.07 and higher, so I won't waste everybody's time.

Other than LG probably having deeper pockets than SolarWorld, I think it's pretty much of a wash, but I'd still go w/ string inverters.

[randomuser]

My decision was also between SolarWorld and LG panels. The cost difference wasn't enough for me to make the simple decision to choose the less expensive option. I don't know if it makes a difference but LG's warranty is a little longer. Also, I don't know if the solvency of the companies matter, as from everything I read here, if the panels hit 2 years without problems, they'll last their expected life, not failing due to infant mortality, so SolarWorld just needs to be around for the next 2 years. My decision to go with LG came down to less roof penetrations. I don't know if this is a valid criteria to make a decision on a system but roof leak fear is my biggest worry about solar. Maybe the POCO changing the rules, where solar is a waste of money is a close second.

Cool, looks like LG 320W panels are what all the installers must be quoting now. I signed a contract for 315W panels but my city took awhile to approve the permit, where I saw people mentioning 320W panels here. I asked my installer if it's possible to get the newer panels. I was prepared to hear "no" because the contract is already signed or the price would be jacked up so much to make me not consider it. The reply was, "Sure, and don't worry about difference in price. We'll just give you the larger panels. Sorry the permit is taking so long." I wonder if LG is discounting the new panels to drive excitement for the newest, latest panel? Most companies charge a premium for the latest and greatest, so it's cool if it's just my installer taking care of me.

[Anjen]

Radomuser can you PM me who you are using, and if you paid closer to the $3 range.

[Anjen]

Other than LG probably having deeper pockets than SolarWorld, I think it's pretty much of a wash, but I'd still go w/ string inverters.

One of the quotes I received was for string inverters (two of them, because of two different facing positions on three different roofs). My main concern with line inverters is the inverter fails now long will I be without a replacement, since that side of the system will be completely down. The argument for micro inverters (from sales) seems to be that if they go down the rest work. Also their other argument is that you can monitor the system accurately because each panel shows usage (although I don't see myself caring about this as much as how much I am offsetting from my bill every month).

The suggestion from one salesperson was SolarEdge Technologies String inverter with LG 320 panels.

[J.P.M.]

One of the quotes I received was for string inverters (two of them, because of two different facing positions on three different roofs). My main concern with line inverters is the inverter fails now long will I be without a replacement, since that side of the system will be completely down. The argument for micro inverters (from sales) seems to be that if they go down the rest work. Also their other argument is that you can monitor the system accurately because each panel shows usage (although I don't see myself caring about this as much as how much I am offsetting from my bill every month).

The suggestion from one salesperson was SolarEdge Technologies String inverter with LG 320 panels.

Opinions vary. I string inverter is one failure point. 20 micros is 20 failure points. The string inverter can be protected in a building. The micros will sit on a roof in what is about the most severe climate on a home - usually the hottest. Electronics don't care much for a lot of heat. The novelty of monitoring usually fades quickly. Micros often carry longer warranties than string inverters. However, like all warranties, they mostly suck and are geared toward the mfg., particularly in the case of micros, often and commonly not covering labor. Read any and all the warranties very carefully. Commonly, no shade - no micros and string inverters are usually and often, but not always specified.

[Anjen]

I don't "think" I have any significant shading. There aren't any large trees blocking the sun on my roof tops. Shading occurs naturally as the sun moves across (rise to sunset). But all South or all West would shade the same way because of that movement. I agree the monitoring novelty would fade VERY QUICK. As for warranty, the string although a lower length of longevity is probably easier to swap out. On paper it seems it would only require disconnect the old (couple lines) and putting in a new, which I could ultimately have an electrician do.

[J.P.M.]

On paper it seems it would only require disconnect the old (couple lines) and putting in a new, which I could ultimately have an electrician do.

How do you propose (on paper) getting at micros that are on panels located away from the outside of an array in say, a 4 X 4 array for example ?

If a tile roof, do you want folks rooting around on it ? Who pays for tile breakage ? etc.

What happens if/when another micro fails ? Same considerations ?

[FFE]

I believe anjen is saying a string inverter is easy to change out.