31 months of solar production graphed...

[MrVivekB]

Moderator: I'm posting a link, but this isn't and literally never will be a monetized channel. YouTube just doesn't pay that much, and I personally despise ads. If this isn't allowed, my apologies, I can just upload the powerpoint used.

If anyone else is also a data geek and is interested, a few months back I created a youtube with 31 months of data. Below are the actual slides if you don't want to hear the melodious sound of my voice

 

[DrSmile]

What size is your inverter? Do you have any shading? Do your panels all face South or do they face mutliple directions? I make 17.5MWh per year on 13.4 KW panels and an 11.4 KW inverter in Northern NJ, so your production is low if you have all South facing panels that are unobstructed. My projected production was 16MWh so I'm overproducing by about 9.3%. My production would be higher if my system didn't go offline on hot days because of PSE&G grid issues.

Your usage numbers are super low IMHO. We have 2 Tesla model 3s and it's not unusual for them to use 60-70 Kwh if both are driven that day. I always recommend to completely cover your roof with panels if you plan on buying an electric car.

 

[MrVivekB]

What size is your inverter? Do you have any shading? Do your panels all face South or do they face mutliple directions? I make 17.5MWh per year on 13.4 KW panels and an 11.4 KW inverter in Northern NJ, so your production is low if you have all South facing panels that are unobstructed. My projected production was 16MWh so I'm overproducing by about 9.3%. My production would be higher if my system didn't go offline on hot days because of PSE&G grid issues.

Your usage numbers are super low IMHO. We have 2 Tesla model 3s and it's not unusual for them to use 60-70 Kwh if both are driven that day. I always recommend to completely cover your roof with panels if you plan on buying an electric car.

How do I determine the inverter size? No shading at all. Panels all face East/SouthEast.

Yeah, the under production is an issue, esp as I just put the order in for a model 3 on saturday. The original estimate would have resulted in 120% of consumption on the house, the salesperson at the time thought it was more than sufficient to handle the EV. The SolarCity acquisition hadn't yet been truly completed, so I'm guessing they weren't that familiar with EVs.

 

[ZBB]

Your declining peak production could be a factor of panel degradation. Check the panel warranty to see if its in spec...

 

[charlesj]

My comment is the weather differences for the same month in the 3 years posted. Without knowing the exact sun Watt out to your panels in those months hard to say degradation is it not the weather.
While I don't have daily data at my fingertip I do have monthly spreadsheet for almost 10 years of operation; I am in the 10th year, have 10 same months to compare starting this past April as I went on line 30 Mar 2012.
When I compare which May or June of those 10 I have no idea if degradation is part of it mostly instead of weather. My first May 2012 was best month for 2012 and so far is the best May of 10 May month I have. In 2020, May was the 3rd best May month production with the other 7 Mays being all over the place in ranking.
First year July, 2012, is now in 8th place of the 10 Julys with 2017 being the best of the 10. I have similar experiences with other months as well.
While I am but one example I'd suggest that you really don't have enough data to compare to indicate degradation is it.

I am also looking at your monthly production. The first 2 July seems to be very close on that graph with 3rd not far down.
So far, 2nd year Dec is your lowest.

 

[MrVivekB]

My comment is the weather differences for the same month in the 3 years posted. Without knowing the exact sun Watt out to your panels in those months hard to say degradation is it not the weather.
While I don't have daily data at my fingertip I do have monthly spreadsheet for almost 10 years of operation; I am in the 10th year, have 10 same months to compare starting this past April as I went on line 30 Mar 2012.
When I compare which May or June of those 10 I have no idea if degradation is part of it mostly instead of weather. My first May 2012 was best month for 2012 and so far is the best May of 10 May month I have. In 2020, May was the 3rd best May month production with the other 7 Mays being all over the place in ranking.
First year July, 2012, is now in 8th place of the 10 Julys with 2017 being the best of the 10. I have similar experiences with other months as well.
While I am but one example I'd suggest that you really don't have enough data to compare to indicate degradation is it.

I am also looking at your monthly production. The first 2 July seems to be very close on that graph with 3rd not far down.
So far, 2nd year Dec is your lowest.

Yeah, not yet sure what "wisdom" can be obtained with just 3 years, one of which were the epic NorCal is on fire. I've also never squeegee'd the panels, just hosed them. I personally have vertigo so a ladder with a hose is the best I can do, I need to find a seasoned person with the extendo-squeegee things to clean.

I read that cleaning panels wasn't really needed, just hosing, but will try that as it couldn't possibly hurt.

 

[MrVivekB]

Your declining peak production could be a factor of panel degradation. Check the panel warranty to see if its in spec...

yeah, will check, thx.

 

[Zextraterrestrial]

Your declining peak production could be a factor of panel degradation. Check the panel warranty to see if its in spec...

how has smoke haze coverage been in that area the last few summers?
not sure what you mean by one of? the last 3 years have been nasty...depending on where you are

 

[MrVivekB]

how has smoke haze coverage been in that area the last few summers?
not sure what you mean by one of? the last 3 years have been nasty...depending on where you are

well we had one spectacularly bad year where you couldn't even go outside, once at 10am it was all but dark. The other summers weren't that bad.

I've hosed the panels during and after each season but haven't hired anyone to squeegee them.

 

[h2ofun]

well we had one spectacularly bad year where you couldn't even go outside, once at 10am it was all but dark. The other summers weren't that bad.

I've hosed the panels during and after each season but haven't hired anyone to squeegee them.

You are lucky, In the foothills, where I live, it has been bad for years!!!

 

[MrVivekB]

You are lucky, In the foothills, where I live, it has been bad for years!!!

ouch. Yeah, not like that where I am.

 

[h2ofun]

ouch. Yeah, not like that where I am.

If you have been watching purple air, this summer pretty much the first smoke stops around sacramento. I have had plenty of over 300 aqi days. When I was in Lake tahoe 2 weeks ago is was 600. So my solar has been way down. Here is my sensor

Real-Time Air Quality Map | PurpleAir

Real time measurement of air quality on a public map. Useful to community scientists or air quality professionals alike, PurpleAir sensors are easy to install, requiring only a power outlet and WiFi.

www.purpleair.com

 

[MrVivekB]

If you have been watching purple air, this summer pretty much the first smoke stops around sacramento. I have had plenty of over 300 aqi days. When I was in Lake tahoe 2 weeks ago is was 600. So my solar has been way down. Here is my sensor

Real-Time Air Quality Map | PurpleAir

Real time measurement of air quality on a public map. Useful to community scientists or air quality professionals alike, PurpleAir sensors are easy to install, requiring only a power outlet and WiFi.

www.purpleair.com

omg. Ours hasn't been over 120ish that I've noticed, although I don't check all the time. I just hosed the panels off this weekend, haven't yet noticed any difference in production.

I did buy an Awair indoor AQI, so we knew whether to turn on our room air filters. That's nice, those specific ones have a variety of metrics.

 

[gpez]

Thanks for posting this, @MrVivekB! This speaks to me as it's identical to my scenario and how I've evaluated my system. You've done great digging in to the data!

I have an 8.55kw + 1 Powerwall system for backup only, like you mostly worried about a prolonged outage due to earthquakes (we're not at fire risk), and set my "bare minimum" at 6kwh/day with "some comforts" at 12kwh/day. Our normal non-high wattage appliance usage (oven/dryer/EV charging/AC) is about 24wkh/day. We did not opt to back up any of the high wattage appliances so if the grid goes down those won't work either. Our system produced 8,386kWh last year.

I've fully integrated my Powerwall with my z-wave home automation via Homeseer. During an outage when we're not home lights and appliances will turn off to conserve power (IFTTT rules keep track of where my wife and my phones are - if we're gone the home knows). Super helpful to know if we're out of town when the power goes out.

If there is an earthquake in the summer, late spring, or early fall we'll be fine. Outside of that time I realized that we'd only be able to last a few days and needed to augment the system. To that end I purchased as 1250w pure sine wave inverter harness for my 2018 Volt which I can use to power anything within extension cord distance of the garage. This is just to load shed things like the tankless gas hot water heater, garage freezer, and some first floor appliances from the Powerwall to extend it's runtime. I estimate between a full Volt charge and a full tank of gas (which it always is - I never use gas for my commute) I expect to get about 100kwh usable 120v power out of it after conversion losses. Also I can charge the Volt 18.4kWh battery from a level 1 charger during an outage from excess solar production during the day, effectively operating as a second Powerwall.

Finally, most of our cooking could be done with a microwave but we also have a camping stove and a couple of gallons of white gas which should last a long time properly stored. We should be good for many weeks if there's some sort of disaster - quite a good feeling.

 

[MrVivekB]

Thanks for posting this, @MrVivekB! This speaks to me as it's identical to my scenario and how I've evaluated my system. You've done great digging in to the data!

I have an 8.55kw + 1 Powerwall system for backup only, like you mostly worried about a prolonged outage due to earthquakes (we're not at fire risk), and set my "bare minimum" at 6kwh/day with "some comforts" at 12kwh/day. Our normal non-high wattage appliance usage (oven/dryer/EV charging/AC) is about 24wkh/day. We did not opt to back up any of the high wattage appliances so if the grid goes down those won't work either. Our system produced 8,386kWh last year.

I've fully integrated my Powerwall with my z-wave home automation via Homeseer. During an outage when we're not home lights and appliances will turn off to conserve power (IFTTT rules keep track of where my wife and my phones are - if we're gone the home knows). Super helpful to know if we're out of town when the power goes out.

If there is an earthquake in the summer, late spring, or early fall we'll be fine. Outside of that time I realized that we'd only be able to last a few days and needed to augment the system. To that end I purchased as 1250w pure sine wave inverter harness for my 2018 Volt which I can use to power anything within extension cord distance of the garage. This is just to load shed things like the tankless gas hot water heater, garage freezer, and some first floor appliances from the Powerwall to extend it's runtime. I estimate between a full Volt charge and a full tank of gas (which it always is - I never use gas for my commute) I expect to get about 100kwh usable 120v power out of it after conversion losses. Also I can charge the Volt 18.4kWh battery from a level 1 charger during an outage from excess solar production during the day, effectively operating as a second Powerwall.

Finally, most of our cooking could be done with a microwave but we also have a camping stove and a couple of gallons of white gas which should last a long time properly stored. We should be good for many weeks if there's some sort of disaster - quite a good feeling.

Oh we should talk further! I was on CQC (Charmed Quark) but switched to HASS a year ago. I just integrated it with the PowerWall and am deploying zWave switches to surge protectors in each room to shut down all ghost power when it detects grid down.

That's a topic for a different thread, as others may have ideas. I'll start one after my next meeting.