Solar Inverter Undersize

[GRV0928]

The Tesla estimate seems way too low just for clipping, and they estimated that with the original plan for 15kwbof inverters?

Are you in Manoa or one of the other valleys where you just get a lot more localized showers and clouds compared to the rest of the island? I don't think PVwatts can account for that, but maybe local installers do...

When i talked with tesla installer my system supposed to be a powerwall2+ with tesla solar inverter but supply chain is short and they had to reschedule my installation date 3 months longer that I expected…

I live at west side of the Island… Waipahu to be exact… i just want to produce as much i can get from solar since i have a Model X to charge . While reducing my electric bills..

 

[dhrivnak]

System info:

Solar Panels: 43 of 425watt = 18,275 watts
Solar Inverts: 3 of Delta M4-TL-US = 12,000 watts.
Battery: 3 PowerWall 2 = 40.5 KW Storage

I understand that Tesla do clipping to maximize production but my system is doing to much, from 10am - 3:30 my solar output is max out to 12.2kwh either sunny day or cloudy day… i believe that if they put the right size of inverter i will gain about 8-15 more kw production… on a good day while watching the gateway web i seen alot the system will go up to 13.7 kwh but it will go back down to 12.2kwh. My system is being limited because of the inverter they put on.
Also I didn’t get my inspection or PTO yet but my system is already selling to the grid when all my battery are charged up… I don’t see the notifications like everyone have “Self-Consumption Only” on the app…


Sunny day

View attachment 786555

Cloudy day

View attachment 786554

Use PV Watts to run a few simulations and you will likely be surprised an how little you use do to clipping. And rmember the inverters run more efficiently more of the time. We tyoically oversize the DC about 25%.

 

[GRV0928]

Use PV Watts to run a few simulations and you will likely be surprised an how little you use do to clipping. And rmember the inverters run more efficiently more of the time. We tyoically oversize the DC about 25%.

My current dc/ac is 1.52 ratio and when I compare it with 1.3 ratio max (by delta spec) i get 3000kw more… I’ve seen 13.7kw for couple timed mostly 12.7kw and it will pull down to 12.2kw..

 

[dhrivnak]

My current dc/ac is 1.52 ratio and when I compare it with 1.3 ratio max (by delta spec) i get 3000kw more… I’ve seen 13.7kw for couple timed mostly 12.7kw and it will pull down to 12.2kw..

Sorry and yes that is definitely more than I would recommend. 1.25 is fine but 1.5 is hard to justify

 

[dareed1]

My current dc/ac is 1.52 ratio and when I compare it with 1.3 ratio max (by delta spec) i get 3000kw more… I’ve seen 13.7kw for couple timed mostly 12.7kw and it will pull down to 12.2kw..

I'm really not clear on where you are getting your numbers. Using PVWatts for Honolulu, 18.275kW, premium panels, roof mount, and a DC/AC ratio of 1.0, all else default, the result is 25,984 kWh. Using DC/AC ratio of 1.5 it gives 25,515kWh, or a loss of 470kWh over the course of a year. It's less than 2%, and in a couple of years the effect will be even less.

Bear in mind that for your latitude, the peak output power is at the highest around March 15 (assuming that atmospheric losses are not too different in HI from CA). You'll make more energy in June/July because the days are longer, but the peak power at noon will be less than now. Of course that's only when the sky is clear, but in my limited experience the sky is frequently not clear in HI. The fraction of the time when clipping is a possibility is reduced compared to, say, AZ or SoCal.

 

[GRV0928]

I'm really not clear on where you are getting your numbers. Using PVWatts for Honolulu, 18.275kW, premium panels, roof mount, and a DC/AC ratio of 1.0, all else default, the result is 25,984 kWh. Using DC/AC ratio of 1.5 it gives 25,515kWh, or a loss of 470kWh over the course of a year. It's less than 2%, and in a couple of years the effect will be even less.

Bear in mind that for your latitude, the peak output power is at the highest around March 15 (assuming that atmospheric losses are not too different in HI from CA). You'll make more energy in June/July because the days are longer, but the peak power at noon will be less than now. Of course that's only when the sky is clear, but in my limited experience the sky is frequently not clear in HI. The fraction of the time when clipping is a possibility is reduced compared to, say, AZ or SoCal.

Tesla estimated with 17.2kw (the highest package)


partial sunny day, looks like its not really clipping but when I scroll on the app from 9:30am - 3:30pm my system is bouncing between 12-12.7kw/h. it doesn’t look flat on top because the inverter always trying to limit the output to 12kw…


Mostly Cloudy day looks rough because when it’s cloudy day the output will shoot up to 13.7kw and over throttle down to 12kw…



Cloudy and partial rain


It won’t bother me if the clipping is only 1-2 hours but mine is about 4-6 hours, and if u do the math with average losing of 10kw a day and 20 out of 30 days thats 200kw multiply by $0.35 thats about $70 a month that will be deducted on my $800 electric bill…

 

[Ampster]

Your order does not detail how many inverters are in the order. If they estimated that you will generate 17 megaWhrs and you get over 20 or more megaWatt hours, what is the issue?

 

[Ampster]

@GRV0928
I am not a lawyer and this is only practical advice. It seems Tesla made a very conservative estimate of production for what ever reason. It does not appear that they put in writing anything specific except the system size in kW, the price and the estimated production. Is that correct?
If that is the case, there is no case for damages or specific performance to install another inverter. I know that clipping is an annoyance to many people but if my most recent assumptions are correct, forget my earlier advice and focus on the fact that you may have received a good value.
I based my earlier comments on my misunderstanding of the facts that the new system would only produce 17 megaWhs and that your original system was projected to produce 25 megaWhs of energy per year,

 

[tfan2018]

How do I tell what’s my inverter size for my 6.12kW system? There’s no labeling on the inverter

 

[Ampster]

@tfan2018


It should be on your paperwork .

 

[wwu123]

@GRV0928
I am not a lawyer and this is only practical advice. It seems Tesla made a very conservative estimate of production for what ever reason. It does not appear that they put in writing anything specific except the system size in kW, the price and the estimated production. Is that correct?
If that is the case, there is no case for damages or specific performance to install another inverter. I know that clipping is an annoyance to many people but if my most recent assumptions are correct, forget my earlier advice and focus on the fact that you may have received a good value.
I based my earlier comments on my misunderstanding of the facts that the new system would only produce 17 megaWhs and that your original system was projected to produce 25 megaWhs of energy per year,

@GRV0928, just reading through the thread one more time, it's not clear that Tesla ever estimated 25 Mwh with either the old or new inverter setup; those all all coming from folks here plugging numbers into PVwatts or otherwise. Was there an earlier higher estimate that was changed to 17.7 Mwh after the inverter swap?

In any case, it seems like 17.7 Mwh is a conservative hedge by Tesla and probably not accurate for either inverter setup. It is more likely you'd get about 25 Mwh with bigger inverters, and something around 23-24 Mwh with the installed inverters. So in reality, pretty close if not exceeding your annual usage.

But here's the thing, even if the two are equal, it doesn't necessarily mean your entire bill is offset. Unless you're charging your Model X in the middle of the day with a charger that's able to perfectly capture your varying excess production (and I don't know if even the latest Tesla wall chargers do that) - you're going to be pushing excess to the grid mid-day, and pulling some most nights and during the winter months. And I think you're only getting $0.10/kwh pushing out, and paying $0.35-0.40 pulling in later. So the 5-10% lost to clipping would mostly be exported at only $0.10, if you're even allowed to export at all. So not worth much, and was itself never going to be the factor to zero out your bill. Am I misunderstanding?

 

[GRV0928]

thank you everyone for you inputs, the Tesla installer said when inspection is finished they will try to solve or do something about it…

 

[solarpwr]

any updates to this GRV0928? we're in the same situation.

 

[GRV0928]

any updates to this GRV0928? we're in the same situation.

Its almost a month now since inspection is finished but I haven’t received PTO yet… while im waiting i installed a sense energy monitor, it seems tesla monitor is reading more than what is suppose to be, with all 3 solar inverter pushing about 4000w the tesla app show 12.5kw while sense only measure around 12kw. Which sense is more accurate than tesla app…

 

[raineycd]

Tesla installed my system a couple weeks ago, I noticed today that the inverter is 7.6kw and panels are 12.8kw. That's a 1.68 ratio. Hope they do the right thing and fix it. Otherwise will have to sue them. Best ask them upfront what inverter size they are planning on using, this seems to be a common issue.

 

[Vines]

Tesla installed my system a couple weeks ago, I noticed today that the inverter is 7.6kw and panels are 12.8kw. That's a 1.68 ratio. Hope they do the right thing and fix it. Otherwise will have to sue them. Best ask them upfront what inverter size they are planning on using, this seems to be a common issue.

From what I have seen here, I think this is an approved ratio, and Tesla will not likely consider this a problem.

 

[BGbreeder]

Tesla installed my system a couple weeks ago, I noticed today that the inverter is 7.6kw and panels are 12.8kw. That's a 1.68 ratio. Hope they do the right thing and fix it. Otherwise will have to sue them. Best ask them upfront what inverter size they are planning on using, this seems to be a common issue.

As others here have written, and it bears repeating, don't focus on the panel/inverter size, focus on how much power your system is generating relative to what you signed up for. As the old saying goes, "there are many ways to skin a cat", and your specific site details of roof slopes, orientations, and exposure make all the difference to how much power will be generated over the course of a year.

All the best,

BG

 

[buckets0fun]

From what I have seen here, I think this is an approved ratio, and Tesla will not likely consider this a problem.

Sadly, even when they troubleshoot an underproducing system it takes a ton of hand holding to get them to realize how utterly crappy this undersizing of the inverter is.

 

[h2ofun]

Sadly, even when they troubleshoot an underproducing system it takes a ton of hand holding to get them to realize how utterly crappy this undersizing of the inverter is.

Why, you got what you paid for. If they put on more inverter, you would be upset the system cost too much

 

[buckets0fun]

Why, you got what you paid for. If they put on more inverter, you would be upset the system cost too much

Painting with such broad strokes is fun.