6Kw going in soon in Aliso Viejo

[josefontao]

Hi JPM,
I thought PVWatts was meant indeed as a ball-park predictor of what your system will put out. Can you let us know what its for?
From PVWatts website:
Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations.

[J.P.M.]

Hi JPM,
I thought PVWatts was meant indeed as a ball-park predictor of what your system will put out. Can you let us know what its for?
From PVWatts website:
Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations.

"What it's for" is use as a tool to aid in system sizing and design by estimating system output over a long period. Without getting into the dictionary definitional difference between "estimate " and "prediction", if you read the rest of the intro/help screens with PVWatts, the part under "results" and the sub category "cautions for interpreting results", you will see that it is not meant as an estimator of short term performance - short term being probably not less than, say, 5 -10 years with an estimated variation for periods of about a year or so perhaps no better than +/- 10 % or so.

Since Bob's array is only about a year or so old, comparing PVWatts estimates to his relatively short time can be misleading. He could be at least several % either way and still be well within PVWatts estimates. I'm not sure what that would reveal about system performance. Probably that for the relatively short period considered, he did better than PVWatts long term estimate. Seems to fit the definition of trivial result to me.

All this is before discussions about estimating how to modify the PVWatts system loss parameter or what goes into it in such a way that it gets close to the reality of the array being modeled.

Array output is largely dependent on the amount of solar radiation received at the array site. That can and does vary from day/day and year/year. That makes the output no more reliable than long term climate forecasting.

An example of the kind of yr/yr variation in output that is perhaps typical: My array fired up 10/17/2013. After 1 yr. of operation, I began keeping track of output yr/yr for various lengths of time. Since 111/02/2014, the 31 day running total output for comparable 31 day periods, one year to the next has been as low as 76.3% and as high as 116.3%.

PVWatts is an estimator of long term output. To the extent that future long term weather and climate can be predicted, it may do an acceptable job, with the caveat that it may be a bit conservative in its output estimates using that 14% default # for a rerate parameter. Using it as a predictor or comparing its estimates to any short period of time can certainly be done, but doing so will perhaps lead to conclusions that are incorrect and perhaps less than ideal outcomes if acted upon.


Knowledge is power. Read all the help info screens, TMY manual and other referenced material for further info. Those who do will likely learn and more importantly understand why PVWatts output is mostly unreliable for short term output unless a larger than usually acceptable amount of uncertainty is used. The ballpark of acceptability is usually larger than most folks know.

Take what you want of the above. Scrap the rest.

[ph33zy]

1st post so I can view pics. Hi everyone. Starting my research for Solar in Irvine now.

[josefontao]

1st post so I can view pics. Hi everyone. Starting my research for Solar in Irvine now.

Hey ph33zy, I'm in Irvine too. I'll be calling the installers next week. I've been researching this for a good 6 months. I'm finally ready!

[ph33zy]

Hey ph33zy, I'm in Irvine too. I'll be calling the installers next week. I've been researching this for a good 6 months. I'm finally ready!

Awesome. We are in Cypress Village. What size system are you looking to get and can you recommend who you're going with?

[mattwillruss]

Awesome. We are in Cypress Village. What size system are you looking to get and can you recommend who you're going with?

I'm in Stonegate and just have my system installed from the same people that did Bob system (thanks Bob). My system is 6.6 kWh (24x275 and 24 M215). Been producing about 35 kW for the past couple days but still waiting for SCE to put us on net meter.

[ph33zy]

I'm in Stonegate and just have my system installed from the same people that did Bob system (thanks Bob). My system is 6.6 kWh (24x275 and 24 M215). Been producing about 35 kW for the past couple days but still waiting for SCE to put us on net meter.

Matt, could you PM me the info and price you paid? I don't have enough posts yet to PM you.

[J.P.M.]

Matt, could you PM me the info and price you paid? I don't have enough posts yet to PM you.

Or tell all of us so we'll stay up to date ?

[josefontao]

I'm in Stonegate and just have my system installed from the same people that did Bob system (thanks Bob). My system is 6.6 kWh (24x275 and 24 M215). Been producing about 35 kW for the past couple days but still waiting for SCE to put us on net meter.

What panels did you go with?

[silversaver]

I'm in Stonegate and just have my system installed from the same people that did Bob system (thanks Bob). My system is 6.6 kWh (24x275 and 24 M215). Been producing about 35 kW for the past couple days but still waiting for SCE to put us on net meter.

The same installer start using LG 280W panel with M250 since May, why settle with 275W +M215? No wonder Dave says "shhh, don't tell them..."

[mattwillruss]

The same installer start using LG 280W panel with M250 since May, why settle with 275W +M215? No wonder Dave says "shhh, don't tell them..."

I signed the contract with them at the end of March. It took almost 2 months to get it back from HOA. In Irvine, the city will need 2 inspections, after you have the rack installed then final inspection. I was quoted with SW 275 but on MyEnlighten is show SW280. I will check with them tomorrow on what the panel did they actually install.

[mattwillruss]

Or tell all of us so we'll stay up to date ?

signed at the end of March at 3.25/DC watt before tax rebate.

[J.P.M.]

signed at the end of March at 3.25/DC watt before tax rebate.

Thank you.

[josefontao]

signed at the end of March at 3.25/DC watt before tax rebate.

Took nearly 4 months? Wow

[ph33zy]

signed at the end of March at 3.25/DC watt before tax rebate.

I actually have an appointment with AI on Monday. Friend went thru them 3 years ago and is happy so far.

Out of curiosity, why is everyone so secretive about who they went with? Is it Solar etiquette to not post in public?