Comments on 7.2kw system in San Diego

[J.P.M.]

Yes... I want to get on the roof this weekend and re-verify level now that it has been up a couple of weeks and had a chance to settle, get some pictures of the installation in general. I'll get a shot of the south-facing view as well, perhaps there is a source of reflection to explain some of the difference in readings.

That the data is consistently ~ 5.5 to 6.5% higher at your end compared to mine sort of makes me think the difference is not due to albedo augmentation which I'd think would vary over the course of a day. I'm not saying which data is more/less accurate, but there is a difference in the GHI of about 6% or so, and like Inetdog or Mike suggested, this is similar to the situation of having 2 watches and never knowing what time it is.

You have another site near you with similar GHI to yours, and I have one (Boulder Knolls on the Weather Underground) close to me that agrees pretty much with my data. That would suggest to me the diff. is location, but 6+ % or so is a whopper of a consistent albedo caused GHI boost. On the other hand, if your data is more accurate, that would make your array instantaneous efficiencies lower, perhaps lower than spec, which would not be my first suspect.

But, your daily clear day output pretty much constantly runs about 57-59 % of my output for an array that's (3.12/5.232)= .596 as large with my orientation perhaps being a tiny bit more favorable, and my roof temps generally being bit cooler from your data.

My GHI model and my sensor data seem to agree fairly well with the NREL Bird model, and seem to give reasonable and consistent fouling #'s in my searches in that area, keeping in mind that if anyone gets within 1% of repeatability, that's about as good as one can expect with the best equipment available, and even that may be a real stretch under the best of conditions. If my GHI was 6% low, my efficiencies, which are about what I'd expect, would be unreasonably high with cell STC's >21.2%.

On albedo effects at either your or my end, reflections could be from any direction or from any source that's above the plane of the sensor, including forward scatter from objects to the north of the array, particularly if "uphill".

Are we having fun yet ?

[J.P.M.]

Like some of you posted, part of the "exceeding predictions" is due to SE's metering. Also, PVWatts default losses seem excessive, and I believe the LG panels probably fall somewhere between Premium and Standard. By the time I have 1 full year (March 5th) I should be at around 13.3 mwh or so, x .97 to correct metering error still brings me back to about 12.9. Selecting Premium panels and reducing losses to 9.15% gets PVWatts to 12.7 mwh. Pretty close considering all the variables, including weather.

The main cause of my over production is the large decrease in my consumption. I'm certainly not going to try to use more energy, but won't be putting a lot of effort into reducing.

As for price, I was initially at $3.55/w, but decided to upgrade the service panel, increasing the price to $3.76/w before tax credit. I did get a Sunpower bid from the same company that installed my LG panels, and it added an almost 25% premium.

Thank you. Running PVWatts w/a smaller derate, ~ 6-10% or so, seems to get closer to actual vs. PVWatts estimates for clear days and new(er) arrays. FWIW, mine's about 8% or so.
For me, SAM runs LG 300's about 0.5% or so better than S.P. 327's on a kWh/yr. per nameplate kW basis for clear days. That agrees pretty well w/ my clear day model which matches SAM quite well using Miramar data.

All this looks to me like more data showing S.P. ain't worth the premium based on greater output/$ spent up front.

[ericf1]

Like some of you posted, part of the "exceeding predictions" is due to SE's metering. Also, PVWatts default losses seem excessive, and I believe the LG panels probably fall somewhere between Premium and Standard. By the time I have 1 full year (March 5th) I should be at around 13.3 mwh or so, x .97 to correct metering error still brings me back to about 12.9. Selecting Premium panels and reducing losses to 9.15% gets PVWatts to 12.7 mwh. Pretty close considering all the variables, including weather.

The main cause of my over production is the large decrease in my consumption. I'm certainly not going to try to use more energy, but won't be putting a lot of effort into reducing.

As for price, I was initially at $3.55/w, but decided to upgrade the service panel, increasing the price to $3.76/w before tax credit. I did get a Sunpower bid from the same company that installed my LG panels, and it added an almost 25% premium.

[sensij]

BTW: Sensij, did you see my post about your irradiance readings ?

Yes... I want to get on the roof this weekend and re-verify level now that it has been up a couple of weeks and had a chance to settle, get some pictures of the installation in general. I'll get a shot of the south-facing view as well, perhaps there is a source of reflection to explain some of the difference in readings.

[jflorey2]

Appreciate any comments or recommendations!

In Santee you are in a pretty good location for solar. You'll see higher temperatures than the coastal area (=slightly lower power) but you'll avoid most of the June gloom that plagues the coastal areas. If you see power interruptions in your area you might want to consider one of the SMA inverters that provides a backup power supply.

[J.P.M.]

[QUOTE=sensij;n303756]
The lower consumption is sort of interesting. Conventional wisdom is that people increase their consumption with an array, because, free power. I think there is a segment of the population that actually becomes more efficient, because their electrical awareness is substantially higher if time was taken during the PV planning to understand more about how residential energy works. /QUOTE]

Just a thought.: I do believe most folks will increase their consumption when solar is added on the idea that the perceived cost of supplying power will be less. But I wonder if some segment of users will decrease absolute consumption - those being the folks who begin to monitor daily consumption. That thought being based on my believe that if you want to improve something, keep an eye on it and measure it regularly - what's measured will probably improve, in this case, go down.

BTW: Sensij, did you see my post about your irradiance readings ?

[sensij]

FWIW, the discussion earlier in the thread about overstated production numbers by SolarEdge has been proven with revenue grade monitoring. When looking at their energy report, it is likely to be 3-4% overstated. The power report is better, usually agrees within 1% on clear days, although it drifts a bit throughout the day.

ericf1, nice to see your first year in the books! Because your system came online within two months of mine, I've found it to be a decent reference system for my own array. Some insight into fouling / degradation may come from the relative performance of our arrays as I get my past my 1 year mark as well, 6 weeks from now. Since then I've added an irradiance sensor to my roof to help calibrate the models, but I've got some work to do (and some questions to answer that have been asked in other threads) before I can report much against that.

The lower consumption is sort of interesting. Conventional wisdom is that people increase their consumption with an array, because, free power. I think there is a segment of the population that actually becomes more efficient, because their electrical awareness is substantially higher if time was taken during the PV planning to understand more about how residential energy works. If you are really interested, you can download your net consumption history from SDG&E from the past two years and combine it with your SolarEdge data to see your true consumption, and determine in what months the reduction occurred (testing the "mild summer" hypothesis).

[J.P.M.]

Well, February was my "true-up" month. There were a few issues with start-up and SDG&E, so things are off a bit. First, my system was off for the first 25 days of NEM billing, so I consumed 440 kwh for my first month. Then, they debited my bank account for this 440 kwh. With the incomplete month and billing error, the numbers don't tell the whole story. What they do tell me is I'm over producing. A lot.

Even with less than a full year, and 440 kwh consumption prior to system turn on, I over produced by 2,329 kwh.

I thought I would be a lot closer to zero, and was even generous with the AC once I saw the credit pile building up. Maybe it was the mild and sunny weather, or conservation efforts, or both, but my consumption is down and production is exceeding estimates. I have had excess production every month except the first partial month. Worst month was October at -2 kwh, best was April at -603 kwh.

3 weeks short of a full year, I'm at 12.9 mwh total production per SE Portal.

As suggested by prior posts to your threads, that production was somewhat predicted and mostly in line with the suggestion that LG and Sunpower systems will produce about equal annual output around here of about 1,700 kWh/yr per installed kW or so for unshaded south facing @ ~ 20 deg. tilt. I suspect you're getting a couple % or so boost in production from reflection off the patio roof.

To the degree that vendor supplied monitoring is the be believed, looks like you're at ~ 12,900/7.2 ~ 1,792 kWh/kW.

As a loose comparison, my stuff put out ~ 1,745 kWh/kW for the prior 365 days using S.P. 327's @ 195 az., 18.75 deg. tilt.

Looking through your older posts, I couldn't find your installed price/Watt for the LG's. Care to share it ? When you purchased/installed, the best S.,P. price around was ~ $4.50/Watt.

[ericf1]

Well, February was my "true-up" month. There were a few issues with start-up and SDG&E, so things are off a bit. First, my system was off for the first 25 days of NEM billing, so I consumed 440 kwh for my first month. Then, they debited my bank account for this 440 kwh. With the incomplete month and billing error, the numbers don't tell the whole story. What they do tell me is I'm over producing. A lot.

Even with less than a full year, and 440 kwh consumption prior to system turn on, I over produced by 2,329 kwh.

I thought I would be a lot closer to zero, and was even generous with the AC once I saw the credit pile building up. Maybe it was the mild and sunny weather, or conservation efforts, or both, but my consumption is down and production is exceeding estimates. I have had excess production every month except the first partial month. Worst month was October at -2 kwh, best was April at -603 kwh.

3 weeks short of a full year, I'm at 12.9 mwh total production per SE Portal.

[ericf1]

Ericf1

Could you PM me your company name you went with?

Calvin

Sure, PM on the way.

[Cyang]

Name of your company

After talking to six installers, I'm settling in on a proposal/bid for a 7.2kw system inland from San Diego (92071). The plan includes 24 LG300N1C-G3 panels, a Solar Edge SE7600 inverter and P300 Power Optimizers on my south facing, 18 deg roof. My current annual usage is about 12,600 kwh, so this system should cover my usage. I guess I could save a few bucks going with the SE6000 inverter, but I like the idea of having room for growth without replacing the inverter.

I like the monitoring of the Solar Edge system, and don't mind spending a little extra for it, but my roof will see very little shading. Am I throwing money away with this system, or making it unnecessarily complex? My impression so far is that Solar Edge equipment is pretty solid, but they have not been in the US long enough to establish long term reliability. I also received a quote using Sunpower 245 panels, but just can't see the 25% premium paying off.

Appreciate any comments or recommendations!

Eric

Ericf1

Could you PM me your company name you went with?

Calvin

[Alisobob]

cool.JPG

I'm right there with ya'!!

[ericf1]

I Finally received my first full month bill from SDG&E since powering up the system. We had plenty of sun, but it stayed cool enough to minimize running the AC. Net usage was -603kwh. My system was off during all but the last 5 days of my first month of net metering, so I came into this month with 440kwh used, so now I'm at -163kwh. On my best day, I generated 50kwh and had a net use of -33.635kwh. Looks like I should be able to generate plenty of credit to run the AC as much as I want this summer.

bill.jpgDaily energy use.jpgbest day.jpg

[DanS26]

Guys, if you want accuracy you need a utility grade meter. Those inverter readings are just plain crap.

Two ways of going about accurate readings....get a utility meter and install in line or get a utility grade CT system installed in your distribution panel.

This company has all the right equipment at the right price...contact them.

http://www.hialeahmeter.com/

[J.P.M.]

I don't think is the inverter itself. Inverter actually report at actual output without any loss or power consume by inverter itself. It is the monitoring system.

For those who have solaredge system, at end of the day, check both reading from inverter and monitoring software.

I'd agree with the monitor reporter as the (possible) culprit. That's what I was trying to say, I think. Fingers faster than brain. My bad.