Everything Solar Forum

I understand it is frustrating to look at an ideal solar day and see clipping. The point I am trying to make is that if you step back, take the emotion out of it, and look at what the impact really is, that in most cases the clipped energy is negligible, and the most optimal design trade-offs usually involve some slight clipping. That is, the best return on your investment, the highest energy production without overpaying for more inverter than you need.
Another way to look at it: Inverters come in specific AC capacities, i.e. 7.6kW, 11.4kW, and in your case, 9kW (or 9.4kW, although the capacities with hybrid inverters such as yours can vary based on the function they are doing, i.e. off-grid, with grid assist, generator, etc).  So if you design an array to pair with an inverter and come up with a price, for a system that will rarely clip, say 0.05% of the annual energy lost due to clipping, it will cost $xx. That is all fine and good, but add a few more solar panels has a low delta cost and will often directly pay for itself at a much higher return than the return calculated for original quoted system (as long as you can use the energy or get net metered for it, of course).  So designers upsize the array because the economics are favorable to do so. Upsizing the inverter does not have the same payback, because you only need more inverter capacity for a small portion of the time that the system operates in a year.  So more solar panels = benefit at all times the system is operating (except a little less benefit during the infrequent clipping time), whereas more inverter = benefit ONLY during potential clipping time.

Here is another way to look at this using logic and math.  I don't know where you live in GA, but I ran a PVWatts simulation for Georgia and it defaulted to a climate data station near Macon Georgia. I ran a simulation for a 12.8kW array with premium panels, oriented due south at 30degrees tilt, with default efficiency losses and with a DC/AC ratio of 1. It calculated annual production of 19,186 kWh. Then I changed the DC/AC ratio to 1.33, such as you have with your system. Annual production dropped to 19,142. This is what the PVWatts model shows will be lost to clipping with the parameters as entered, in the middle of Georgia. I am not saying it is completely accurate for your particular system and site, because the parameter inputs may need to be tweaked to match your situation.  But this does illustrate that clipping is often far less impactful than we thik, when you look at it analytically. 44kWh per yhear x $.13/kWh = $5.72 per year. At that rate, you need a ton of years to make up for the cost of replacing your inverter.  And, your array will degrade over time and so the clipping impact will lesson over time.

Another way to look at it, I downloaded the hourly data from the PVWatts simulation described above, brought it into excel, and counted the number of hours that the array power would exceed certain values.. There were only 155 hours when it exceeded 10,000W, and 24 hours when it exceeded 11,000W. Again PVWatts is a basic simulation tool and the simulations are only as good as the inputs are realistic/accurate for the application/situation.  Still, there are 8,760 hours in a year.  Somewhere around 4,380 daylight hrs in a year. Do you want to design for 24 or even 155 hrs out of that 4,380? Or do you want to design for the 4,200 non-ideal hours of the year that your system will spend the vast majority of it's time operating in?
If your answer is that I don't care about the economics and optimizing payback, and I just don't want to see any of my array energy not being used ever, then that is a perfectly acceptable conclusion for you. I am just trying to provide guidance and answers to your original questions that I feel are relevant.

@Ken Nadsady Maybe this will help. 
As far as the inverter, Even though I may not be able to squeeze much more juice from it right now, when my central heat kicks in, it spikes to just over 14kw. Now, my 12k can hold a 10 second surge up to 16kw, but in an off grid situation (This is really what I installed solar for, not for "energy savings" or to go green, but SHTF scenario) that means I'm not using my central heat. Can I survive, sure. I've got gas heaters and 2 stand up portable A/C units with heaters that draw way less power. But, again, the decision would have to be for the price can I just upgrade to a bigger inverter and not worry about having to do any of that, and get more PV production, and be able to sell at my max rate of 10k. I'm actually limited to grid sell 9400w right now with the 12k inverter.

If it's a few thousand dollars, I'm 100% prepared to make the upgrade. If its $10k...I'll just be happy with what I got lol. My installer is already ordering me 2 additional batteries because I just want a little more reserve power. Right now I'm usually hitting my 80% DOD right around the time we wake up in the morning, so those 5-10 additional kWh will hopefully be right on target. That may not even be close to sufficient during the summer, but we'll see. 

I understand it is frustrating to look at an ideal solar day and see clipping. The point I am trying to make is that if you step back, take the emotion out of it, and look at what the impact really is, that in most cases the clipped energy is negligible, and the most optimal design trade-offs usually involve some slight clipping. That is, the best return on your investment, the highest energy production without overpaying for more inverter than you need.
Another way to look at it: Inverters come in specific AC capacities, i.e. 7.6kW, 11.4kW, and in your case, 9kW (or 9.4kW, although the capacities with hybrid inverters such as yours can vary based on the function they are doing, i.e. off-grid, with grid assist, generator, etc).  So if you design an array to pair with an inverter and come up with a price, for a system that will rarely clip, say 0.05% of the annual energy lost due to clipping, it will cost $xx. That is all fine and good, but add a few more solar panels has a low delta cost and will often directly pay for itself at a much higher return than the return calculated for original quoted system (as long as you can use the energy or get net metered for it, of course).  So designers upsize the array because the economics are favorable to do so. Upsizing the inverter does not have the same payback, because you only need more inverter capacity for a small portion of the time that the system operates in a year.  So more solar panels = benefit at all times the system is operating (except a little less benefit during the infrequent clipping time), whereas more inverter = benefit ONLY during potential clipping time.

Here is another way to look at this using logic and math.  I don't know where you live in GA, but I ran a PVWatts simulation for Georgia and it defaulted to a climate data station near Macon Georgia. I ran a simulation for a 12.8kW array with premium panels, oriented due south at 30degrees tilt, with default efficiency losses and with a DC/AC ratio of 1. It calculated annual production of 19,186 kWh. Then I changed the DC/AC ratio to 1.33, such as you have with your system. Annual production dropped to 19,142. This is what the PVWatts model shows will be lost to clipping with the parameters as entered, in the middle of Georgia. I am not saying it is completely accurate for your particular system and site, because the parameter inputs may need to be tweaked to match your situation.  But this does illustrate that clipping is often far less impactful than we thik, when you look at it analytically. 44kWh per yhear x $.13/kWh = $5.72 per year. At that rate, you need a ton of years to make up for the cost of replacing your inverter.  And, your array will degrade over time and so the clipping impact will lesson over time.

Another way to look at it, I downloaded the hourly data from the PVWatts simulation described above, brought it into excel, and counted the number of hours that the array power would exceed certain values.. There were only 155 hours when it exceeded 10,000W, and 24 hours when it exceeded 11,000W. Again PVWatts is a basic simulation tool and the simulations are only as good as the inputs are realistic/accurate for the application/situation.  Still, there are 8,760 hours in a year.  Somewhere around 4,380 daylight hrs in a year. Do you want to design for 24 or even 155 hrs out of that 4,380? Or do you want to design for the 4,200 non-ideal hours of the year that your system will spend the vast majority of it's time operating in?
If your answer is that I don't care about the economics and optimizing payback, and I just don't want to see any of my array energy not being used ever, then that is a perfectly acceptable conclusion for you. I am just trying to provide guidance and answers to your original questions that I feel are relevant.

@Ken Nadsady Maybe this will help. 
As far as the inverter, Even though I may not be able to squeeze much more juice from it right now, when my central heat kicks in, it spikes to just over 14kw. Now, my 12k can hold a 10 second surge up to 16kw, but in an off grid situation (This is really what I installed solar for, not for "energy savings" or to go green, but SHTF scenario) that means I'm not using my central heat. Can I survive, sure. I've got gas heaters and 2 stand up portable A/C units with heaters that draw way less power. But, again, the decision would have to be for the price can I just upgrade to a bigger inverter and not worry about having to do any of that, and get more PV production, and be able to sell at my max rate of 10k. I'm actually limited to grid sell 9400w right now with the 12k inverter.

If it's a few thousand dollars, I'm 100% prepared to make the upgrade. If its $10k...I'll just be happy with what I got lol. My installer is already ordering me 2 additional batteries because I just want a little more reserve power. Right now I'm usually hitting my 80% DOD right around the time we wake up in the morning, so those 5-10 additional kWh will hopefully be right on target. That may not even be close to sufficient during the summer, but we'll see. 

Robert I can tell you are intelligent and have really done your homework.  If you are into math and would like to investigate further, you absolutely do have access to PVWatts.   Just go to https://pvwatts.nrel.gov/pvwatts.php and you can do your own modeling and what-if analysis. You can download the hourly production data and crunch the numbers yourself.

As for solar not making sense in GA, I am not sure I agree with that blanket statement.  Battery storage adds significant cost to a system and does little for the economics. The value of storage in most locals in the US is the energy it provides when the grid is down.  In California or other spot markets that hav TOU it can add more economic benefits, but not for most.  Straight up grid tie solar maker sense economically in most every market, and I suspect in GA as well. What is your cost per kWh?  I know assymetric net metering rules in some markets reduce the benefit, but usually it still makes sense.
Good luck!

I understand it is frustrating to look at an ideal solar day and see clipping. The point I am trying to make is that if you step back, take the emotion out of it, and look at what the impact really is, that in most cases the clipped energy is negligible, and the most optimal design trade-offs usually involve some slight clipping. That is, the best return on your investment, the highest energy production without overpaying for more inverter than you need.
Another way to look at it: Inverters come in specific AC capacities, i.e. 7.6kW, 11.4kW, and in your case, 9kW (or 9.4kW, although the capacities with hybrid inverters such as yours can vary based on the function they are doing, i.e. off-grid, with grid assist, generator, etc).  So if you design an array to pair with an inverter and come up with a price, for a system that will rarely clip, say 0.05% of the annual energy lost due to clipping, it will cost $xx. That is all fine and good, but add a few more solar panels has a low delta cost and will often directly pay for itself at a much higher return than the return calculated for original quoted system (as long as you can use the energy or get net metered for it, of course).  So designers upsize the array because the economics are favorable to do so. Upsizing the inverter does not have the same payback, because you only need more inverter capacity for a small portion of the time that the system operates in a year.  So more solar panels = benefit at all times the system is operating (except a little less benefit during the infrequent clipping time), whereas more inverter = benefit ONLY during potential clipping time.

Here is another way to look at this using logic and math.  I don't know where you live in GA, but I ran a PVWatts simulation for Georgia and it defaulted to a climate data station near Macon Georgia. I ran a simulation for a 12.8kW array with premium panels, oriented due south at 30degrees tilt, with default efficiency losses and with a DC/AC ratio of 1. It calculated annual production of 19,186 kWh. Then I changed the DC/AC ratio to 1.33, such as you have with your system. Annual production dropped to 19,142. This is what the PVWatts model shows will be lost to clipping with the parameters as entered, in the middle of Georgia. I am not saying it is completely accurate for your particular system and site, because the parameter inputs may need to be tweaked to match your situation.  But this does illustrate that clipping is often far less impactful than we thik, when you look at it analytically. 44kWh per yhear x $.13/kWh = $5.72 per year. At that rate, you need a ton of years to make up for the cost of replacing your inverter.  And, your array will degrade over time and so the clipping impact will lesson over time.

Another way to look at it, I downloaded the hourly data from the PVWatts simulation described above, brought it into excel, and counted the number of hours that the array power would exceed certain values.. There were only 155 hours when it exceeded 10,000W, and 24 hours when it exceeded 11,000W. Again PVWatts is a basic simulation tool and the simulations are only as good as the inputs are realistic/accurate for the application/situation.  Still, there are 8,760 hours in a year.  Somewhere around 4,380 daylight hrs in a year. Do you want to design for 24 or even 155 hrs out of that 4,380? Or do you want to design for the 4,200 non-ideal hours of the year that your system will spend the vast majority of it's time operating in?
If your answer is that I don't care about the economics and optimizing payback, and I just don't want to see any of my array energy not being used ever, then that is a perfectly acceptable conclusion for you. I am just trying to provide guidance and answers to your original questions that I feel are relevant.

@Ken Nadsady Maybe this will help. 
As far as the inverter, Even though I may not be able to squeeze much more juice from it right now, when my central heat kicks in, it spikes to just over 14kw. Now, my 12k can hold a 10 second surge up to 16kw, but in an off grid situation (This is really what I installed solar for, not for "energy savings" or to go green, but SHTF scenario) that means I'm not using my central heat. Can I survive, sure. I've got gas heaters and 2 stand up portable A/C units with heaters that draw way less power. But, again, the decision would have to be for the price can I just upgrade to a bigger inverter and not worry about having to do any of that, and get more PV production, and be able to sell at my max rate of 10k. I'm actually limited to grid sell 9400w right now with the 12k inverter.

If it's a few thousand dollars, I'm 100% prepared to make the upgrade. If its $10k...I'll just be happy with what I got lol. My installer is already ordering me 2 additional batteries because I just want a little more reserve power. Right now I'm usually hitting my 80% DOD right around the time we wake up in the morning, so those 5-10 additional kWh will hopefully be right on target. That may not even be close to sufficient during the summer, but we'll see.