solar production

[sevusal]

so i just have my new system PTO last Saturday (just under a week ago). since then the weather in SF bay area has been very cloudy and rainy. we had a couple of days of good sun (in 60s) and I noticed even during those days the production was only ~2.5KWh while my system is capable of doing 3.8Kwh. is it normal? is there a way I can compare my solar production with other people in my area?

so here is an output from today. around 12-3 the weather was 60-61 and sunny. the max production at that time was only 2.5Kwh.

 

[gnumeric]

I’m also in the SF Bay Area (South Bay). Production in the winter is pretty crappy. Here’s my production from today to compare. I have a 5.08 kW system and the highest output I hit today was 3.7 kW at 11:55am.

It’ll get better once winter passes.

 

[sevusal]

I’m also in the SF Bay Area (South Bay). Production in the winter is pretty crappy. Here’s my production from today to compare. I have a 5.08 kW system and the highest output I hit today was 3.7 kW at 11:55am.

It’ll get better once winter passes.

View attachment 504079

Thanks. so your 'at moment production' is around 72% while mine is around 65% (below Tesla guidance). May I ask what kind of panels and inverter you have installed? I have Delta with Q.Peak panels. wondering if that could be the reason?

 

[gnumeric]

Thanks. so your 'at moment production' is around 72% while mine is around 65% (below Tesla guidance). May I ask what kind of panels and inverter you have installed? I have Delta with Q.Peak panels. wondering if that could be the reason?

I have a Delta inverter with 315W Panasonic panels. I had my system installed back in August 2018 when they were still using those panels.

 

[sevusal]

I have a Delta inverter with 315W Panasonic panels. I had my system installed back in August 2018 when they were still using those panels.

Makes sense given they have dropped the solar pricing last year.

 

[Sylvia Else]

To get anywhere the theoretical maximum, the panels have to be perpendicular to the sun. At this time of year in the Bay area, the sun is only getting to a bit more than 33 degrees above the horizon. Unless your roof is very steep, your panels are going to be far from perpendicular. The variation in output suggests either some cloud or, given the low sun angle, shadows, which will make things worse.

In the summer you should do a lot better, but even then any offset of your roof from being south facing is going to affect the result.

 

[gnumeric]

I wouldn’t worry too much about it. Today I was surprised I even got higher than 3kW. These past couple months have usually been in the 2kW range.

Like Sylvia said, it could also be due to the angle of your roof. My roof faces almost perfectly south. Google Sun Roof has it as the brightest yellow/almost white.

 

[sevusal]

To get anywhere the theoretical maximum, the panels have to be perpendicular to the sun. At this time of year in the Bay area, the sun is only getting to a bit more than 33 degrees above the horizon. Unless your roof is very steep, your panels are going to be far from perpendicular. The variation in output suggests either some cloud or, given the low sun angle, shadows, which will make things worse.

In the summer you should do a lot better, but even then any offset of your roof from being south facing is going to affect the result.

Thanks. Are people uploading the usage somewhere for comparison?

 

[sevusal]

I wouldn’t worry too much about it. Today I was surprised I even got higher than 3kW. These past couple months have usually been in the 2kW range.

For reference, during the summer I usually peak at around 4.2kW.

I wouldn’t worry too much about it. Today I was surprised I even got higher than 3kW. These past couple months have usually been in the 2kW range.

It could also be due to the angle of your roof. My roof faces almost perfectly south. Google Sun Roof has it as the brightest yellow/almost white.

Oh! Good to know. Feeling little relieved now!

 

[jjrandorin]

so i just have my new system PTO last Saturday (just under a week ago). since then the weather in SF bay area has been very cloudy and rainy. we had a couple of days of good sun (in 60s) and I noticed even during those days the production was only ~2.5KWh while my system is capable of doing 3.8Kwh. is it normal? is there a way I can compare my solar production with other people in my area?

so here is an output from today. around 12-3 the weather was 60-61 and sunny. the max production at that time was only 2.5Kwh.

View attachment 504078

As was said, the answer to your question is "its winter, much less production at that time... systems are rated for yearly production. Days are also shorter now than they will be later in the year. There is likely no issue at all with your new system, this is normal"

I have had my system since 2015. My system size is 8.7 kWh. Right now, on a perfectly sunny day, I generate about 25 kWh a day. This same system, in the middle of march, will be low 40s, and in June-july, its 48-52.

If you live in a place that requires A/C during the summer, your best time for energy will be March to May/June since production will be high, and you wont need AC during those times. If you are watching your system like a hawk, you can actually see production ebb and spike when clouds pass by sometime.

 

[Ampster]

Thanks. Are people uploading the usage somewhere for comparison?

You can go to PVWATTS and load your location and system parameters into their website and get an estimate for each month.

 

[cwied]

Thanks. Are people uploading the usage somewhere for comparison?

Check pvoutput.org to see what other systems are producing.

 

[sevusal]

Thankyou!

 

[charlesj]

To get anywhere the theoretical maximum, the panels have to be perpendicular to the sun. At this time of year in the Bay area, the sun is only getting to a bit more than 33 degrees above the horizon. Unless your roof is very steep, your panels are going to be far from perpendicular. The variation in output suggests either some cloud or, given the low sun angle, shadows, which will make things worse.

In the summer you should do a lot better, but even then any offset of your roof from being south facing is going to affect the result.

Yep, he would need a 57 deg roof

 

[charlesj]

You are not that far away from me.
Keep in mind, the shortest day is Dec 20/21 and longest day Jun 20/21.
Here in Monterey, the difference in daylight is 5 hrs. that will determine the total best day collection.
My best peak kWh was on 14 May 2012 at 3.86 kWh. Nothing so far beats it.
My system is probably very close in total production to yours and yesterday's peak, while not full sun, it was nice, was 2.8 kWh.
As you can see from my best day and yesterday a full kWh.
Also, how south does your system faces? Mine is at 190 deg with an 18 deg roof, a 4/12 pitch.

 

[Sylvia Else]

Yep, he would need a 57 deg roof

Where I live, in Australia, I've seen quite a few such roofs. I think the owners mistakenly thought they'd emigrated to Austria where such a roof might make sense (because of snow).

 

[Dan123]

Thanks. Are people uploading the usage somewhere for comparison?

Your production seems normal for January. I am in Florida and my max is about 70-75% in January of the theoretical max.

You can go to pvoutput.org and look for systems near you to compare.

 

[Mardak]

Tesla has a page about seasonality factors:
Solar Panels Monitoring | Tesla Support

Generally if you consider Winter the base amount, you can double that amount to estimate for Spring and Fall and triple the base amount for Summer.

 

[charlesj]

Well, on a sunny day in Dec/Jan I get about 15 kWh and in summer it can be 26 kWh with my most being 27.6.
Summer temperatures decreases production as well if you had the same winter temp on the roof.
I don't see any doubling on my lat. Florida would have a much higher sun angle in winter than in NorCal

 

[Monterey808]

Well, on a sunny day in Dec/Jan I get about 15 kWh and in summer it can be 26 kWh with my most being 27.6.
Summer temperatures decreases production as well if you had the same winter temp on the roof.
I don't see any doubling on my lat. Florida would have a much higher sun angle in winter than in NorCal

Hey charlesj, in the process of getting a new roof and a medium Tesla solar panel setup. Live in Monterey myself and was wondering how close you are to generating what the system was designed for.