Our solar production

[Caracalover]

Congratulations on the new house and well-made system. We're over the mountains from you and that sounds pretty good. What is the total size (# of panels x rating of panels) and orientation of your array? We have 6300 Watts (DC) oriented due South and saw a bit over 37kWh for the same day. Check your Sunday production; Our's totaled over 40kWh with very clear skies and cold winds all day long. The warmer calm weather of Monday dropped production almost 10%. Full disclaimer: We see days >40kWh only 3-4 times a year, but it is great when they occur. The meter literally flies backwards without the summer need for air conditioning.

I don't know enough about it yet to really answer this, still moving in and haven't taken the time to figure the whole thing out yet. There are 25 panels, and they hadn't been cleaned in a couple years. I hosed them down and used a soft brush on them the other day, which is when I got the 33KWH number. Didn't wash them till mid day though, so my numbers may have improved over the last few days, haven't been checking.

Is there a right way to wash them, and does anyone dry them to prevent water spots?

Thank you for the congratulation - any chance I will see you at the cathouse (I think I gave you a card a long time ago) Saturday night? It is the first Twilight Tour of the year. Wildcatzoo.org (Shameless plug) - And yes I take my Leaf there, although they do not have a charger for public use.

 

[wsbca]

Is there a right way to wash them, and does anyone dry them to prevent water spots?

I've rinsed mine with a hose maybe twice in 20 months, otherwise relying on the (infrequent) rain to clean them off. They are too high up to get near them to do any drying - it doesn't seem to be a problem. One tip is don't rinse them when they are really hot - it's neat to see the efficiency zoom up for a few minutes when they get cooled down, but they are so hot that putting cold water on the glass is probably not a good idea. I think the need for washing or not really depends on your location/environment - some places are a lot dustier than others.

Depending on their vintage, your panels are probably rated somewhere between 210 and 230 watts DC (for example my Sunpower panels are 215's) - if you can determine the model you'll be able to google the detailed specs - in fact the model name/number will probably have the wattage as part of the name. So your nominal system rating is somewhere between 5 and 5.75kW DC (25 * 2xx). The conversion to AC results in a loss of about 14% give or take, so your AC peak sustained generation will be between 4.3 and 5kW. With the odd number of panels I'm not sure what to guess about your inverter - is it a large unit with a Sunpower nameplate? If so it's probably a re-badged Sunny Boy, with a 5kW or 6kW AC rating, though I'm a little confused by the odd-numbered count of 25 panels, I don't know how that would be broken into "strings"...if the system is new, it's possible you have micro-inverters on each panel rather than a single big inverter on your wall, but that's a relatively recent trend.

Anyway, with a few more details on your hardware the particulars of your system's capacity and likely output can be worked out. The 33kWh you made the other day would be about 6.6 "solar hours" at an AC rating of 5kW - that's exactly what I'm getting right now on a fully clear day - other factors beyond the rating are your latitude, panel orientation and temperature. An annual average of 5 "solar hours" per day is a common estimate in the continental U.S. - many folks will do better than that but it's what is used in most back-of-the-envelope estimates by installers, assuming reasonable panel orientation and no persistent unhelpful weather patterns. I'm getting 5.4, my neighbor with better panel orientation and more inverter headroom gets around 6.

 

[dgpcolorado]

...Is there a right way to wash them, and does anyone dry them to prevent water spots?...

FWIW, After spraying with a hose I use a window squeegee on a long painter's pole. And I do dry my panels after washing by draping a towel over the squeegee because I have hard water where I live.

I mostly use the squeegee/pole for pulling snow off the panels, which is something you don't have to fuss with. But dust storms in the Arizona/Nevada/Utah desert west of my house lead to mud rain and snow at times so the dirt does build up on the panels on occasion.

 

[tjenkens]

I have a 20 panel (Sharp 230 w) with micro inverter on each panel. My roof faces due south and is a 45 degree pitch. On the sunniest days the array will hit 4000 watts (its max) for a brief time mid day. Here is a link to the Enlighten website with my array's real-time output: https://enlighten.enphaseenergy.com/public/systems/6kvJ15573" onclick="window.open(this.href);return false;

 

[Caracalover]

Is there a right way to wash them, and does anyone dry them to prevent water spots?

I've rinsed mine with a hose maybe twice in 20 months, otherwise relying on the (infrequent) rain to clean them off. They are too high up to get near them to do any drying - it doesn't seem to be a problem. One tip is don't rinse them when they are really hot - it's neat to see the efficiency zoom up for a few minutes when they get cooled down, but they are so hot that putting cold water on the glass is probably not a good idea. I think the need for washing or not really depends on your location/environment - some places are a lot dustier than others.

Depending on their vintage, your panels are probably rated somewhere between 210 and 230 watts DC (for example my Sunpower panels are 215's) - if you can determine the model you'll be able to google the detailed specs - in fact the model name/number will probably have the wattage as part of the name. So your nominal system rating is somewhere between 5 and 5.75kW DC (25 * 2xx). The conversion to AC results in a loss of about 14% give or take, so your AC peak sustained generation will be between 4.3 and 5kW. With the odd number of panels I'm not sure what to guess about your inverter - is it a large unit with a Sunpower nameplate? If so it's probably a re-badged Sunny Boy, with a 5kW or 6kW AC rating, though I'm a little confused by the odd-numbered count of 25 panels, I don't know how that would be broken into "strings"...if the system is new, it's possible you have micro-inverters on each panel rather than a single big inverter on your wall, but that's a relatively recent trend.

Anyway, with a few more details on your hardware the particulars of your system's capacity and likely output can be worked out. The 33kWh you made the other day would be about 6.6 "solar hours" at an AC rating of 5kW - that's exactly what I'm getting right now on a fully clear day - other factors beyond the rating are your latitude, panel orientation and temperature. An annual average of 5 "solar hours" per day is a common estimate in the continental U.S. - many folks will do better than that but it's what is used in most back-of-the-envelope estimates by installers, assuming reasonable panel orientation and no persistent unhelpful weather patterns. I'm getting 5.4, my neighbor with better panel orientation and more inverter headroom gets around 6.

The system was installed in 2007, and the sticker on the side of the inverter says it is a Model spr 6000M http://solarhub.com/inverters/385-SPR-6000m-SunPower" onclick="window.open(this.href);return false;

Thanks for the information! I got 34.7 KWH as of 7PM today, so I am pretty happy. I am also in Southern CA, now in Tujunga rather than Altadena. The house also came with solar water heaters, so some of the roof that could have been power creation is being used for water heat instead. Seems to be working great, but may have been the reason for an odd number of panels. One is by itself below the water heating unit. I could post a photo if you are interested, but it would not be until next week.

 

[HighDesertDriver]

Is there a right way to wash them, and does anyone dry them to prevent water spots?

The system was installed in 2007, and the sticker on the side of the inverter says it is a Model spr 6000M http://solarhub.com/inverters/385-SPR-6000m-SunPower" onclick="window.open(this.href);return false;

Thanks for the information! I got 34.7 KWH as of 7PM today, so I am pretty happy. I am also in Southern CA, now in Tujunga rather than Altadena. The house also came with solar water heaters, so some of the roof that could have been power creation is being used for water heat instead. Seems to be working great, but may have been the reason for an odd number of panels. One is by itself below the water heating unit. I could post a photo if you are interested, but it would not be until next week.

I'm going to guess that your panels are also Sunpower. Sunpower systems differ from most, if not all, of the rest of the industry in that they are positively instead of negatively grounded. In 2007, Sunpower inverters were the the only available inverters for their panels.

The difficulty that I and some of the other posters are having is making sense of the configuration. For efficiency reasons, panels are normally connected in series (like flashlight batteries) to get the highest practical direct current voltage the the installed inverter. Each series of panels is called a "string" and then equally-sized strings (i.e., the same voltage) are then connected in parallel at or just before the inverter. The only possibility for a single inverter at your home would be 5 strings of 5 panels, but this would be an unusually choice because the inverter would be operating at less than optimum efficiency. One string of 25 would exceed the both the panel and inverter limits; anything else would have unequal voltages. The good news is that it seems to be working pretty well, so focus on getting moved in and leave the details for us curious types for later.

As for washing, we limit it to 1-2 times per year and hope for rain for the times in-between. The only exceptions are the rare times when our home has been downwind of large fires and received large amounts of ash and debris "fallout." I first wet down the panels with a hose, scrub them with a window washer mop to loosen the dirt, and then hose them off again. I sometimes wrap the mop head with a towel to push off water beads, but we do not seem have mineral build-up, whether I do or don't. The one thing I do not do is attempt to squeegee off the water. I'm just not comfortable maneuvering a hard-cornered object on the end of a long semi-flexible pole near tempered glass on expensive panels. :shock:

 

[keydiver]

Seems to be working great, but may have been the reason for an odd number of panels. One is by itself below the water heating unit.

That extra panel by itself, below the solar hot water heater panel, is probably to run the pump for circulating the hot water. So, what you probably really have is 2 strings of 12 panels each. At perhaps 230-270 watts per panel, that would give you 5520-6480 watts DC, close to your inverter's 6000 watt output rating. You lose ~15% in the conversion efficiency.

 

[HighDesertDriver]

Seems to be working great, but may have been the reason for an odd number of panels. One is by itself below the water heating unit.

That extra panel by itself, below the solar hot water heater panel, is probably to run the pump for circulating the hot water. So, what you probably really have is 2 strings of 12 panels each. At perhaps 230-270 watts per panel, that would give you 5520-6480 watts DC, close to your inverter's 6000 watt output rating. You lose ~15% in the conversion efficiency.

I believe you get the Columbo award. It is likely that when a picture is posted we will see that this odd panel is also much smaller than the 24 in the main array.

 

[dgpcolorado]

The one thing I do not do is attempt to squeegee off the water. I'm just not comfortable maneuvering a hard-cornered object on the end of a long semi-flexible pole near tempered glass on expensive panels. :shock:

Having watched grape sized hail bounce off my panels, which are rated for golf ball sized hail I believe, tapping them with something like the metal back of a squeegee is hardly a concern. Fragile that glass is not. And the rubber part of a squeegee extends beyond the ends of the holder so there is no reason to hit them with the metal anyway. But plastic squeegees are available for those worried about it.

I'd be more concerned about spraying cold water on very hot panels, as wsbca cautioned against above. Tempered glass shouldn't be affected by that, but why take the chance?

 

[N952JL]

April has been a good month here in Middle GA. Out of 11 days, 7 has seen outputs between 62 kWh and 68 kWh, then two days above 55 kWh and two between 31 and 35 kWh, for a eleven day total of 634.470 kWh. My meter is now showing a net usage back to the end of Feb. Since my electric company only pays me .043 cents per kWh I sell to them, when I get enough credit, I'll turn on the pool heater and warm up the pool with my excess. (I have to pay .095 cents kWh).

I have 48 Everygreen 210's feeding two 6000W Sunnyboy inverters. But if I had to do it over, I would look very closely at micro inverters as I loose two hrs of sunlight in the evening to shade from trees. Shade on one panel brings down the rest in the series. Here in Middle GA Temps will get me in July thru Sept as the higher temps bring down my daily output to below 60. 55.327 was my best daily yield during July 2011, and only 10 days in the fifties.

 

[TonyWilliams]

I have 48 Everygreen 210's ..... 55.327 was my best daily yield during July 2011, and only 10 days in the fifties.

I can do this with 35 228w Sumpower Serengettis and M190's Enphase.

 

[KLQL8N]

I live in Phoenix and we have an 8.1 Kw system made up of 30 x 270 panels connected to a SunnyBoy 7000.
Our data is posted at
http://pvoutput.org/list.jsp?userid=4692

We have had the system up for 2 years this July. Phoenix is really dusty...so when the wind blows or it rains the panels get dirty!!
In the Spring and Summer I wash panels when the daily total is not increasing or is not the same as the previous weeks' rate indicating the production is not as efficient.
This decrease in production is due either to increasing heat or dirty panels.
I have tried 3 different ways of cleaning the panels.
1. Hosing - does not remove bird doo. Left the panels hazy. Don't know if that is a problem or not.
2. Used Windex Upper Story Window Cleaner Pads - rinsed really clean without spots. Pad falls off by the third string.
3. Used plain ole diluted vinegar and ammonia solution and scrubbed with a push broom - rinsed well, but broom is heavy and too short to reach some of the panels.

I googled cleaning panels awhile ago and found that "Google" completed a study on comparing panels installed in California at different angles from horizontal to 45 degrees.
The horizontal panels had a significant decrease in production as they became dirty. Google found that panels installed on an angle productivity did not decrease signicantly over the same period of time. I am assuming where these panels were installed, the rain was clean and rinsed the panels on the angle!!

Had I known then what I know now...I would have left more room around the panels so I could maintain them more safely. One set is too close to the edge for me to reach with the broom. Good thing I like the view from the roof!! I am working on a cleaning system that won't require a person hosing the panels!! Anyone else already have a non-human cleaning system in place?

 

[DaveEV]

I live in Phoenix and we have an 8.1 Kw system made up of 30 x 270 panels connected to a SunnyBoy 7000.
Our data is posted at
http://pvoutput.org/list.jsp?userid=4692

Nice! Mine is here: http://pvoutput.org/list.jsp?userid=7058" onclick="window.open(this.href);return false;

And I've just set up a Nissan LEAF Owners team that might be fun to get LEAF Owners to join: http://pvoutput.org/listteam.jsp?tid=384" onclick="window.open(this.href);return false;

I googled cleaning panels awhile ago and found that "Google" completed a study on comparing panels installed in California at different angles from horizontal to 45 degrees.
The horizontal panels had a significant decrease in production as they became dirty. Google found that panels installed on an angle productivity did not decrease signicantly over the same period of time. I am assuming where these panels were installed, the rain was clean and rinsed the panels on the angle!!

Yes, having the panels mounted at sufficient mounting angle is key to keeping them clean. The morning dew is enough to move dirt around, but if the panels are mounted flat (or near flat), the dirt has no where to go because of the raised edge holding the panel together. I estimate that a 10* mounting angle is sufficient to avoid that. My panels are mounted nearly flat - my roof that they are mounted on is sloped about 3* and what happens is that dirt tends to accumulate on the bottom row of cells on each panel. If the panels were mounted at even 5* the effects of this dirt build-up would be minimal. Knowing this now, I would have made much more of an effort to get the panels tilted a bit more.

Luckily, it's not too dusty around here and with Enphase micro-inverters it's pretty easy to see when they are getting dirty - usually a panel or two will start underperforming about 5-10% compared to the rest, then I'll go up with there with a California duster and a towel and simply wipe the dirt away. Takes about a minute per panel - I can be up on the roof, clean the panels, and back down in less than 30 minutes. But I usually take my time and enjoy the view. This is typically needed about twice a year, but if my panels were mounted at more of an angle, I don't think I'd really need to go up at all to clean them.

 

[Yanquetino]

Today I received my first utility bill since taking delivery of my Leaf, and was delighted to see that my array still produced more juice than I used.

CarWings tells me that, up to the date of the bill, I used 154.1 kWh to drive 794.2 miles. That amounts to... 5.15 miles per kWh... or 19.4 kWh per 100 miles.

That's in the right ballpark, I guess. The bill claims that I used 140 kWh more this month than one year ago without the Leaf. Regardless, the solar put a 525 kWh surplus into the grid. I guess I've got to drive more!

 

[keydiver]

Best solar day EVER! The cooler temperatures combined with a blue-sky, cloudless day, with low humidity, to put my system at >62kWh for the day! That's more than 10% greater than my previous record. So far this month I've banked about an additional 100 kWh to save up toward the A/C bill this summer.

 

[DaveinOlyWA]

Best solar day EVER! The cooler temperatures combined with a blue-sky, cloudless day, with low humidity, to put my system at >62kWh for the day! That's more than 10% greater than my previous record. So far this month I've banked about an additional 100 kWh to save up toward the A/C bill this summer.

wow that is "250 Leaf" Miles!!

 

[N952JL]

Best solar day EVER! The cooler temperatures combined with a blue-sky, cloudless day, with low humidity, to put my system at >62kWh for the day! That's more than 10% greater than my previous record. So far this month I've banked about an additional 100 kWh to save up toward the A/C bill this summer.

Luckly you. My utility company will not let me bank from one month to the next. If I product more than I use, they issue me a credit @ .044 per kWh and I carry a credit ballance into the next month. While that may sound like I can "bank", it isn't, as they charge me .095 per kWh when I use it. So when I bank from one month to the next I get 1/2 hr for every hr I give them. I plan on using my excess to heat the pool. (April, May, and Oct are the three months I produce more than I can use.)

 

[hill]

I live in Phoenix and we have an 8.1 Kw system made up of 30 x 270 panels connected to a SunnyBoy 7000.
Our data is posted at
http://pvoutput.org/list.jsp?userid=4692

We have had the system up for 2 years this July. Phoenix is really dusty...so when the wind blows or it rains the panels get dirty!!
In the Spring and Summer I wash panels when the daily total is not increasing or is not the same as the previous weeks' rate indicating the production is not as efficient.
This decrease in production is due either to increasing heat or dirty panels.
I have tried 3 different ways of cleaning the panels.
1. Hosing - does not remove bird doo. Left the panels hazy. Don't know if that is a problem or not.
2. Used Windex Upper Story Window Cleaner Pads - rinsed really clean without spots. Pad falls off by the third string.
3. Used plain ole diluted vinegar and ammonia solution and scrubbed with a push broom - rinsed well, but broom is heavy and too short to reach some of the panels.

I googled cleaning panels awhile ago and found that "Google" completed a study on comparing panels installed in California at different angles from horizontal to 45 degrees.
The horizontal panels had a significant decrease in production as they became dirty. Google found that panels installed on an angle productivity did not decrease signicantly over the same period of time. I am assuming where these panels were installed, the rain was clean and rinsed the panels on the angle!!

Had I known then what I know now...I would have left more room around the panels so I could maintain them more safely. One set is too close to the edge for me to reach with the broom. Good thing I like the view from the roof!! I am working on a cleaning system that won't require a person hosing the panels!! Anyone else already have a non-human cleaning system in place?

Some city reg's require panels to be set back from the sides ... the ridge ... and/or the bottom of the roof line - reasoning that if someone's up there walking around, you have a bit of wiggle room to get around more safely ... and you're less likely to damage your panels. Our city also gave the rational that panel setbacks made roof access easier (potentially) for fire department. IMO that seemed kind of funny when I first heard it because if the fire department is going up there to chop a vent hole (maybe right where the panels are anyway) ... then a walkway that prevents 'damage' is kind of a moot point.

 

[QueenBee]

Some city reg's require panels to be set back from the sides ... the ridge ... and/or the bottom of the roof line - reasoning that if someone's up there walking around, you have a bit of wiggle room to get around more safely ... and you're less likely to damage your panels. Our city also gave the rational that panel setbacks made roof access easier (potentially) for fire department. IMO that seemed kind of funny when I first heard it because if the fire department is going up there to chop a vent hole (maybe right where the panels are anyway) ... then a walkway that prevents 'damage' is kind of a moot point.

Yeah, this was a fun exercise for me. My city currently says that the setbacks are "requested" so I was able to ignore them which was nice since my southern roof is so small it would have drastically reduced the number of panels I could fit. The setback from the ridge is definitely beneficial to the fire department. They vent the attic through the roof at the ridge so having that setback provides an area to do that. Depending on which way the wind is blowing they might want to do it on one side of the ridge over the other. The setback from the bottom and sides of the roof are probably just a bit over the top. Sure they make access easier but if you want to get on the roof you probably would prefer to get on the side that has no solar panels than to walk on a narrow setback.

Anyway, the rumor that I heard last year was when the international build standards (I forget the official name/abbreviation) comes out with its next revision they are going to add the setback to the code and then it'll become a requirement "everywhere". Hopefully with some logically thinking people will be able to get exemptions to it when it makes sense.

 

[RegGuheert]

March 2012 was our best month ever, and also was the first month that we have spun the meter backward, in spite of the addition of the LEAF mid-month!

Well, April 2012 set all new records for our system: The highest production in a single day was 67.0 kWh on April 6, and the monthly number was also a record. Average daily production came in at 49 kWh/day. (The system was turned off last April while we waited for the power company to replace the meter with one that didn't count up regardless of the direction of the power flow.)

Here are our numbers so far this year:

January 2012: 870 kWh
February 2012: 1080 kWh
March 2012: 1350 kWh
April 2012: 1470 kWh
-----------------------------
2012 Total: 4770 kWh