Is there any reason that you only go for 66%. In Virginia (not sure the law in NJ), you can go up to 150%, and my system is designed to provide 130% offset.
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Anyone have solar other than Tesla solar?
- Thread starter itsallaboutme
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charlesj
Active Member
Not sure why they recommended 66% maybe because my bills were $85-95 before getting the Tesla's and $140 ish after but the summer is a factor in that price.
Not sure why they recommended 66% maybe because my bills were $85-95 before getting the Tesla's and $140 ish after but the summer is a factor in that price. I have a call scheduled with them for Monday to ask. I am not familiar with offset and why I would need more or less.
They should have asked you about last year's energy consumption from your energy company and calculated your projected/proposed production.
When I went through the beginning steps it asked for my login to my electric company so hopefully they looked at last years consumption. I will ask them.
(following is opinion post only, others may differ)
One of the worst places one can be in, in regards to buying solar (at least in my opinion) is buying it but not getting enough to fully offset not only your current bill but as much of your expected increase as you can.
Its human nature, but when people get solar, their electricity usage always goes up.. never down. Significant others / children in the house start leaving lights on more, and any request to go back to conserving is met with "but we have solar now, dont we?".
Additionally, if you dont try to offset 100% of your current usage (by offset that means "generate"), you end up in the situation where you have solar, have to conserve still, and also still have significant bills from the utility.
Couple that with the fact that there will be a push for more electrification (perhaps another EV etc) and also the fact that you will not simply be "adding panels" if you decide later you want more solar, and you have a recipe where you should get "as much as you can afford and fit on your roof, up to about 110-120% offset".
I personally would not purchase or accept a system that was only supposed to cover that little of my usage "right now" let alone any future increases.
With that all being said, its important to remember these are construction projects. There may be technical reason why they only suggested 66% (roof lines, etc), but I would push back on that if it were me.
One more reminder that this is just my personal opinion, and I am not trying to put myself forth as an expert or anything.
Thanks for the info. Also forgot to mention since I live in NJ there is no tax that was a surprise to me. When I bought my Tesla's we didn't get taxed either but I did not know it would also be for solar panels.
Silicon Desert
Well-Known Member
He didn't say anything about HOA blocking him. He said "I like it because we live in a condo and locally installed solar is not possible."
This is the case in some locations where a person in a condo or townhouse shares the roof with other owners. A solar installation can be prevented in many of those cases.
charlesj
Active Member
I suppose then the roof surface over his physical space is not enough? I have heard other condos being able to do so but perhaps not the best direction.
Silicon Desert
Well-Known Member
Perhaps yes in some cases. I only know of 2 instances (one is a family member and the other is a friend) that I looked into the situation with them as to why they were not allowed to put solar on their roof. One was in California and the other in Tennessee. In one case, an owner lived directly above the other owner (a townhouse) and since they were both responsible for maintaining the roof, one owner did not want to allow the solar. It was in their CC&R before they bought the property. In the other case, owners lived side by side. still, same legal issue.
I suppose there are probably plenty of opposite examples where it is not an issue. Just saying an owner may not always have the ability to install solar as dependent on several factors.
Yep, this is why I Put on as much as I could fit and get approved. Happens to be WAY over my current usage
Late to the party. Like the OP, I'm in New Jersey. Solar panels and inverters went in in 2008 and are still up there and functioning. Company is Trinity Heating & Air, based in Freehold, NJ. 9 kW on the roof; 7.8 kW max output.
They came in cheaper and had a better plan. No issues with "pay on time" or "we take the SRECs and you pay reduced electricity". We paid cash on the barrel head (from a loan.. but we paid off the loan very early). We had a roof leak a couple years later; they came on down in a hurry, found the spot, tarred it, and it's still working fine.
Interesting bit, though: In NJ, at that time, the general rule is that, using this complicated equation, one is not supposed to generate more energy from one's solar panels than, in the year previous, one got from the electric company. We had fifteen months or so of electric bills, working out to about 10 MW-hr's worth of energy a year. The system put into play was supposed to generate that much, taking into account angle of the roof, number of panels, losses in the wires and inverters, average cloud cover and solar irradiation data courtesy of NASA, and so on. If one violates the paper equation limit, one wouldn't get SRECs.
So.. after a couple years of having the panels in, we're noticing that the panels are generating 12 MW-hr's of electricity a year. Huh?
So, was at a home show, wandered by one of the solar installer tables. (By the by: Home shows are a great place to run into solar installers, if one is so inclined.) Told them we had a system already, ya-ta-da. And then asked, "So, after all that complex PC-based equationing, how come we've got a couple of extra MW-hr's a year?". The four guys all looked at each other, one grinned, and they told me: The equation's government mandated, clearly got an error in it, but nobody wants to fix it.
Helps when owning a Tesla. The M3 gets 250 W-hr per mile, so those 2 MW-hr extra equates to 8000 miles of free running around the landscape, not bad.
They came in cheaper and had a better plan. No issues with "pay on time" or "we take the SRECs and you pay reduced electricity". We paid cash on the barrel head (from a loan.. but we paid off the loan very early). We had a roof leak a couple years later; they came on down in a hurry, found the spot, tarred it, and it's still working fine.
Interesting bit, though: In NJ, at that time, the general rule is that, using this complicated equation, one is not supposed to generate more energy from one's solar panels than, in the year previous, one got from the electric company. We had fifteen months or so of electric bills, working out to about 10 MW-hr's worth of energy a year. The system put into play was supposed to generate that much, taking into account angle of the roof, number of panels, losses in the wires and inverters, average cloud cover and solar irradiation data courtesy of NASA, and so on. If one violates the paper equation limit, one wouldn't get SRECs.
So.. after a couple years of having the panels in, we're noticing that the panels are generating 12 MW-hr's of electricity a year. Huh?
So, was at a home show, wandered by one of the solar installer tables. (By the by: Home shows are a great place to run into solar installers, if one is so inclined.) Told them we had a system already, ya-ta-da. And then asked, "So, after all that complex PC-based equationing, how come we've got a couple of extra MW-hr's a year?". The four guys all looked at each other, one grinned, and they told me: The equation's government mandated, clearly got an error in it, but nobody wants to fix it.
Helps when owning a Tesla. The M3 gets 250 W-hr per mile, so those 2 MW-hr extra equates to 8000 miles of free running around the landscape, not bad.
I have no idea, but I wonder if the equation is an "average" of some kind? here in CA for example, its extremely common for a system to generate way more than its kW rating on a yearly basis. My 8.6kW system (for example) generated 13.14 MWh last year (in its 7th year of existence) and has generated 9.4MWh already this year.
This is super common here in CA, so much so that until I joined this board and saw that in other parts of the US, a "9kW" system actually generated around 9-10kW (not 14 like I would expect), I was surprised. I know its because of the amount of sun we get here, etc, but it makes me think that the formula must be some sort of average or something.
At the time, being the EE nerd that I was, I did a lot of digging about solar panel systems, both in 2008 when we got the install, and in 2004 when we moved into the house. In 2004 there was this web site run by the NJ government. In it, one could put in the the numbers of appliances a house had, the square footage, the air conditioning systems and its efficiency, angle on the roof and how many square feet of roofing there was, one's longitude and latitude, and the model would suck in information from NASA on solar irradiation data for the site, including how much cloud cover on average one might have.
Included in all this were the solar panel types, how efficient they were as a function of temperature, and whether they were single crystal or amorphous.
The inverters get to be fun, too. At the time, one would hook up strings of panels, then put the strings in parallel, then connect the whole mess to the inverters. The inverters would "hunt" for the correct voltage and current that gave one maximum power from the panels. Early in the morning or late in the afternoon, there wouldn't be much power from the panels; at noon, there'd be more; but the inverters' efficiencies varied with the power input, the ambient temperature, and so on.
In addition, one has to use copper wires to move the energy from the panels to the inverters.
Losses.. don't tell me about losses. If one has a single string of panels, there's no guarantee that, with a given solar input, that a particular panel's current and voltage will be the same as other panels' currents and voltages. This results in inefficiencies where one can't get the full advertised power from all the panels because the current and running through panel X results in less power than the same current running through panel Y. Then take a string of panels like that and parallel it with another batch of panels. Total power of the panels, if they could all have the same sun energy perpendicular to the surface of the panels, in my system, is 9.02 kW. The actual output power, max, is 7.8 kW. I've watched the power levels go up and down: There really is about 13.5% loss in wires, inbalances, and the inverters. Once or thrice a year the inverters would peak at their maximum output power for a half hour or so around noon, but mostly that never happened, the installers had it all sized about right.
So, when one is designing a system to meet that NJ requirement, one can find on-line designers. Input to the designer: Roof angle. Location, which gives where the sun is over time for the entire year. Average temperatures recovered from databases on Each Day throughout the year. Cloud cover and, throughout the year, on a daily basis, the percentages of days when the air is absolutely clear and when it's foggy.
And, interestingly, the make and model of the panels one is putting up! I've seen the manufacturer's data sheets for these panels. Temperature variations. Power vs. irradiation and, no, it's not linear.
Interestingly, modern setups aren't built like that any more. First off, the panels are monocrystalline: They're black, not mottled blue like mine. The mottled blue ones have amorphous silicon and are cheaper but aren't as efficient. The black ones cost more, but, partly because of economies of scale, the prices have dropped and, since they're more efficient, one needs fewer of them to reach a given power level.
The next huge difference is those power blocks. Like the ones I was talking about with regard to Tesla battery chargers earlier. A given panel is 250W-500W at about 20V or so. One places a DC-DC converter on each panel, then connects the outputs of the DC-DC converters on a string of, say, 10 panels in series. Each DC-DC converter fools around with the current/voltage level on its input until it maximizes the power draw from that particular panel. All the other DC-DC converters are doing the same thing.
So, the output of each DC-DC converter in a string has a different amount of power, since the panels have manufacturing variations. Well, the outputs are all wired up in series, so each has the same current. The modules communicate with each other; the entire string voltage is set to 300V, say; the higher power panels get more of that voltage, the lesser power panels get less of that voltage, and all the panels make the maximum amount of power they're capable of.
Boom! My system has 15% losses: At least 10% of those losses would go bye-bye. There might be 1% loss in each of the DC-DC converters, but we're now 9% to the good, and a system could have 9% fewer panels for the same total output power level.
This also makes the inverters simpler, too. My inverters have to live with voltages that range from 150VDC to 450 VDC as a function of sunlight, and from that, they generate 240 VAC. It's not easy making them efficient over that wide a voltage range. With the individual DC-DC converters on the panels trick, one can keep the DC voltage into the inverters at 300 VDC for most of the range of sunlight intensity that one might run into, so the inverters get more efficient. There's 3% more efficiency, for a total of 12% fewer panels for a given power level.
And now, we get tricky. Do what Tesla does: Make the batteries in their Powerwalls 300V, the same as the panel string voltages. Suddenly, switching back and forth between city power and battery power, and charging batteries in general, gets to be more technically feasible.
Going back to your original question: The equations are complex and there was some flunky, or hired flunky, in NJ that designed and mandated that equation. I suspect that it wasn't reviewed by professionals. And, like I said, once the error was discovered.. what were they going to do? Tell people to put fewer panels on their houses? I mean, these were the people trying to get people to go solar! Even the public utilities didn't raise a fuss.
The rooftop is setup for recreational use with a pavilion, furniture, etc. Not solar friendly.
I thought I was confused before
hopefully when I talk to someone from Tesla they can explain why they recommend 66%I thought I was confused before
I am going to guess its going to be because of stuff like the fact they only install panels in one orientation, the roofline setback requirements, exhaust vents on the roof preventing some panels, etc.
If you ask them "why", you will likely wait a lot longer for an answer than if you said "Please max out my configuration and get back to me with what size that is". "Why" requires someone to interact with a designer, pass on your question, wait for them to get back to you etc ( you will never talk to the tesla system designer, tesla has them blocked off from all personal contact).
"Max out my configuration on my roof" is an actionable task someone can forward on and that group can work on and get back to you with that (less interaction).
If the goal is to get more solar than they quoted you initially, that would be much faster (and if not possible would likely come back with the "why" as a response). Its just how that part of the process works within tesla from what I can see.
roblab
Active Member
I bought 66 panels from Northern Arizona Wind and Sun years ago, built my own mounting frames for my roof and the bank below my house out of pipe, wired the panels myself with 6-3 w/g, ran the wire through the shingles and roof into the attic and thence to my electrical feed. I had an electrician friend do the final hookup and the connections to the three power walls I had bought. and have had no problems for a dozen years. My sister-in-law helped me install them on my roof while in her high heels (she's a kick).
It's not rocket science. Luckily, I live in the county so there's not a preponderance of regulations, but we followed the laws and I have 11 kw of power when the sun shines bright.
I did not use any brand name company other than one inverter from Sunny Boy that was laying around. I'd never heard of Fronius before this, either. You don't have to have anyone sell you a bill of goods if you are able to do some simple wiring and understand a few simple things about electricity.
So, you can just about do it yourself but it's not for everybody.
It's not rocket science. Luckily, I live in the county so there's not a preponderance of regulations, but we followed the laws and I have 11 kw of power when the sun shines bright.
I did not use any brand name company other than one inverter from Sunny Boy that was laying around. I'd never heard of Fronius before this, either. You don't have to have anyone sell you a bill of goods if you are able to do some simple wiring and understand a few simple things about electricity.
So, you can just about do it yourself but it's not for everybody.
