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Website for expected solar panel performance on date and latitude

neoflyer

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Oct 23, 2020
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Is there a website that I can enter a date and my latitude then get expected solar panel performance? I’m thinking it would give a performance factor type report. Example: on September 9 at N36 latitude the performance factor might be 2.6 (or some other number) so a 100 watt panel could produce 260 watts total on a perfectly sunny day. 400 watts of panels would be expected to produce 1040 watts total under those circumstances. Is there any such site for this?

I ask because I just installed 840 watts of panels. In a three day test this week at N36 latitude they’ve produced very close to 1500 watts each day, according to my Victron app for the solar charge controller. That’s less than 1800% of my panel capacity. I’m thinking that seems very low. Am I right?
 
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You can try https://pvwatts.nrel.gov. Do you mean 1500 watt hours? That would be only about 2 total hours of full sun.
- what panels do you have
- how are they wired
- what controller are you using
- what is your nominal battery bank voltage?
 
I ask because I just installed 840 watts of panels. In a three day test this week at N36 latitude they’ve produced very close to 1500 watts each day, according to my Victron app for the solar charge controller. That’s less than 1800% of my panel capacity. I’m thinking that seems very low. Am I right?
What panels output is dependent on many things other than the solar conditions on that day.

In particular solar PV can only generate if it has a load to supply. If the battery is charged and there is not much of a load to feed, then the solar PV output will be curtailed to meet the demand.

This is the normal situation for off-grid set ups.

Grid-tied set ups that have no grid export restriction will generate whatever they can, up to the limit of the inverter's output capacity.

Is there a website that I can enter a date and my latitude then get expected solar panel performance?
There is Solcast:

You can set up a free account and input your PV system's settings and it will provide live estimates as well as a 3 day look back and 3 day forecast of expected production.

But this potential solar PV output only applies if your solar has loads to feed that are at least as much as the panels can potentially generate.
 
As an example of Solcast in action, here's the estimate of my little off-grid system's output:

Screen Shot 2021-09-10 at 3.15.51 pm.png

It said that today at 12:30pm my solar array was capable of outputting 1.53kW.

Now my array normally doesn't produce full output because it's only running a 300W pump and the batteries are typically fully charged in the daytime.

But today I happened to be performing some load tests to see how much I could get out of the PV system. Here's the chart showing one test between 12:23 and 12:29pm, with solar PV output ramping up to 1.57kW at peak.

Screen Shot 2021-09-10 at 3.22.07 pm.png
 
Is there a website that I can enter a date and my latitude then get expected solar panel performance? I’m thinking it would give a performance factor type report. Example: on September 9 at N36 latitude the performance factor might be 2.6 (or some other number) so a 100 watt panel could produce 260 watts total on a perfectly sunny day. 400 watts of panels would be expected to produce 1040 watts total under those circumstances. Is there any such site for this?

I ask because I just installed 840 watts of panels. In a three day test this week at N36 latitude they’ve produced very close to 1500 watts each day, according to my Victron app for the solar charge controller. That’s less than 1800% of my panel capacity. I’m thinking that seems very low. Am I right?
That’s 1500 watt hours and less than 40% of capacity based on time of year and latitude.
 
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