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Getting tesla solar installed today 395w Panel
- Thread starter giran99
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They are being somewhat deliberately misleading. Your system will be limited to a max of 7.6 kW AC output. Around solar noon when your panels would be capable of generating higher power it will be limited by the single inverter and the output will be clipped at 7.6 kW. Away from solar noon and in the winter your system will be putting out more power than if you had fewer panels but still limited to 7.6 kW max so it's not like the extra panels are worthless.
It is generally most cost efficient to have slightly more panel DC power than what the inverter can output although the ratio of your system DC panel power to AC inverter power is higher than you would typically want.
your speced 12.6w of panels will never reach that. So nothing wrong with having more panel specs than the inverter. Inverter can handle it.
As @Rccarps2 points out, 7.6kW at 1.4 DC to AC ratio is 10.64kW...not 12.6, but again with roof slope, and orientation, the system may never hit even that.
i see,so it could work . that's what Tesla is saying . i dont know if i wanna talk to someone else. my original order says 2 inverter 7.6 and 3.8kW
See above about the information that an inverter larger than 10kW puts you into a different rule set that really isn't worth it compared to what you will gain with the second inverter.
The DC input from the panels is what they are talking about. your output will be capped at 7.6KW A/C. I would absolutely insist on a larger inverter or multiple inverters unless you have lots of shading or opposing East/West orientations of the panels. I have all South facing panels and I clip 9 months out of the year with an 11.4 KW inverter and 13.4 KW of panels. See below almost 3 hours of clipping 2 weeks ago. If Massachusetts does cap at 10KW then there is no reason to go much past that (10KW) in DC for a 7.6 KW inverter assuming good panel placement and sun exposure.
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@giran99 I have a couple of questions, the answers thereto might help folks here help you.
BG
- What is your goal here?
- Are you trying to get what was originally quoted, no matter what? (Have you checked the fine print about what Tesla is permitted to substitute?)
- What is the orientation(s) of your panels, and what is your roof angle? This will help folks figure if your panels are ever possibly going to output 12.6kW, or check out PVwatts.com yourself.
- Have you looked into the possible, and indeed probable, problems you will run into going over 10kW of inverter capacity in Massachusetts?
- Are you ok with the additional conditions?
- Is Tesla OK with those changes?
BG
See this thread for lots of related discussion:
11.6kw Solar Roof, but only one Inverter?
I agree with the questions you should ask yourself that @BGbreeder wrote above.
As you will see in the thread I linked to Tesla telling you the inverter can "overdrive" is at best quite misleading and at worst pure BS. It's what they tell you to get you off their backs. If it wasn't for the 10 kW inverter capacity threshold I would push Tesla to honor what they promised when you signed the contract, however given this limit and how it affects on your NEM reimbursement you are probably better off with the single inverter.
11.6kw Solar Roof, but only one Inverter?
I agree with the questions you should ask yourself that @BGbreeder wrote above.
As you will see in the thread I linked to Tesla telling you the inverter can "overdrive" is at best quite misleading and at worst pure BS. It's what they tell you to get you off their backs. If it wasn't for the 10 kW inverter capacity threshold I would push Tesla to honor what they promised when you signed the contract, however given this limit and how it affects on your NEM reimbursement you are probably better off with the single inverter.
The salient point is that you will produce much less power with a single 7.6 KW inverter. You will clip (lose) anything above 7.6 KW. So if your panels are producing say 13 KW on a sunny day, you will be losing 5.4KWh per hour. Depending on your setup this may be significant. With different panel orientations or cloudy days it will be mitigated, but from my experience I would say you're wasting at least 3KW of panels with your setup if all your panels are unobstructed South facing. I would get less panels.
@BGbreeder @DrSmile @Vines Thanks for information and i was able to get data from tesla and pvwatts .. and seems to me i will be ok with 7.6kW inverter. attached file pic of pvwatts data . Thanks and i have learned a lot in few day about solar.
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giran99,
It looks like you did your PVWatts calculation using a DC to AC ratio of 1.2. A 7.6kW inverter on a 12.6kW system is a ratio of 1.66. I ran PVWatts for Boston and didn't get exactly the same annual production that you did, but the difference between 1.2 and 1.66 amounted to just under 4% for a year. So I agree that the 7.6kW inverter should be fine.
It looks like you did your PVWatts calculation using a DC to AC ratio of 1.2. A 7.6kW inverter on a 12.6kW system is a ratio of 1.66. I ran PVWatts for Boston and didn't get exactly the same annual production that you did, but the difference between 1.2 and 1.66 amounted to just under 4% for a year. So I agree that the 7.6kW inverter should be fine.
The extra energy stays in the solar panels because the inverter allows less current from the panels. In effect, the inverter intentionally operates away from the Maximum Power Point of the panels. The elecrtrical power produced by the panels is less, so the inverter doesn't need to dissipate it.
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