David W Virtue
Member
Thanks for sharing your learning daniel. Fascinating posts to me as a sustainable power fan with no installations except an M3 in the garage.
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Switched on my system today!
- Thread starter daniel
- Start date
Okay. I guess that makes sense.
I discovered that if I turn the ceiling fans to high I don't need as much A/C. Not that it really matters since my A/C is free. But it will be good to know the next time there's a power outage.
I just talked to my contractor. He phoned me because he wants to adjust something or put something in or something. Anyway, I asked him about the discrepancy in the daily totals on the Tesla app. Basically, adding up the total solar production, total house consumption, over the course of five days, the app reports that I've consumed roughly 30 kWh more than I've produced. (I've drawn about 1 kWh total from the grid over that time.) The SoC of the Powerwalls does is not very different at bedtime or when I get up, from one day to the next, so the Powerwalls are not contributing more than 5 or 6 kWh to any discrepancy. And since they only hold 13 kWh each total (26 for the two together) this cannot explain the difference.
What my contractor said is that Tesla is just doing a really crappy job of adding up the daily numbers. The Solar Edge app and web site (which he talked me through so that now I can read it) are, he says, much more reliable. I'm drawing very little power from the grid, according to Solar Edge. That's what really matters.
The cottage draws a bit more from the grid. He explained that because with only one Powerwall, it's harder for that system to balance, and needs to draw more, and more often. But it's also possible that he needs to tweak it a bit, and he's going to check that when he comes over.
Yesterday it was very cloudy. That meant I didn't need to use much A/C and the car was not charging because I didn't go anywhere. The result was that my Powerwalls filled up early (I saved more energy by not needing A/C than I lost by cloudy weather) and I was a little annoyed that the utility would not take my excess, since I had capacity. But, I speculate:
Someone commented upthread that Maui Electric only has 30% renewable energy in its mix. But I speculate that most of that is home solar feeding in the excess, and most of that goes into the grid between 9:00 or 10:00 a.m. and 3:00 or 4:00 p.m., when the sun is high. I'll bet that during those hours Maui is probably running on close to 100% renewables, but then the sun goes down and people get home from work, and still need A/C for several more hours, or maybe all night depending on how their house is situated. It may be that without storage, 30% is all that solar can do here. Of course, I'm getting 99% of my power from solar because I have my Powerwalls. But this could explain why new solar installations here on Maui cannot get net metering.
What my contractor said is that Tesla is just doing a really crappy job of adding up the daily numbers. The Solar Edge app and web site (which he talked me through so that now I can read it) are, he says, much more reliable. I'm drawing very little power from the grid, according to Solar Edge. That's what really matters.
The cottage draws a bit more from the grid. He explained that because with only one Powerwall, it's harder for that system to balance, and needs to draw more, and more often. But it's also possible that he needs to tweak it a bit, and he's going to check that when he comes over.
Yesterday it was very cloudy. That meant I didn't need to use much A/C and the car was not charging because I didn't go anywhere. The result was that my Powerwalls filled up early (I saved more energy by not needing A/C than I lost by cloudy weather) and I was a little annoyed that the utility would not take my excess, since I had capacity. But, I speculate:
Someone commented upthread that Maui Electric only has 30% renewable energy in its mix. But I speculate that most of that is home solar feeding in the excess, and most of that goes into the grid between 9:00 or 10:00 a.m. and 3:00 or 4:00 p.m., when the sun is high. I'll bet that during those hours Maui is probably running on close to 100% renewables, but then the sun goes down and people get home from work, and still need A/C for several more hours, or maybe all night depending on how their house is situated. It may be that without storage, 30% is all that solar can do here. Of course, I'm getting 99% of my power from solar because I have my Powerwalls. But this could explain why new solar installations here on Maui cannot get net metering.
Daniel- ask your installer to submit for grid supply or smart export. MECO still has room on those tariffs and your system will work much better than when it’s set up for non export. The way non export works is that the Pv inverter and the powerwall both use their own zero export mechanisms and they don’t always work that well together. One thing is the delay you see in the Pv ramping up when a big load turns on. And the biggest draw back is that a solar edge inverter set up for zero export will not produce power in offgrid mode. What you will see after the 5 minute wake up is the Pv ramp up and then curtail itself to zero. This is because the Pv inverter only produces when it sees a small amount of import from the grid. The sales people don’t make this very clear but with hurricane season approaching it’s an important thing to be aware of. There is a way your installer can tweak the settings on the solar edge so it will produce offgrid but it typically leads to the Pv exporting too much power than what the utility will allow.
My system does produce power when the grid is off. We've verified this by shutting off the grid at the breaker next to the meter. I do see about 0.2 kWh of export per day.
But I will forward your post to my solar guy and see what he says.
I sent my solar contractor your post. He said that he checked, and Smart Export is not available on my street. He also said that Smart Export is "of no use." And he mentioned as I mentioned above, that we did the test and the panels do produce when the grid is off.
What we actually saw was that if the Powerwall is full (which it happened to be when we did the test, as it was about mid-day, after getting a lot of sunlight but before A/C became needed) the solar will remain off until the Powerwall gets down to around 96% SoC. After that, the 5-minutes start, and then the solar comes back on but will not charge the Powerwall above 96% until the grid comes back on. When the grid comes back on, IIRC, the solar shuts off for another 5 minutes.
What Tesla should really do is allow the car to communicate with the gateway and allow us to set the car to charge when there is excess solar, but shut off or dial back when it would be drawing from the Powerwall. Let us charge from the Powerwall if we need the range, but just use solar production otherwise.
During the course of the day I get plenty of solar to run my A/C and charge the car, and at peak production I can do both at once; but there are times when doing both at once draws power from the Powerwalls, which is good that I can do it, but is not as good as linking the car to the gateway and just using the excess.
During the course of the day I get plenty of solar to run my A/C and charge the car, and at peak production I can do both at once; but there are times when doing both at once draws power from the Powerwalls, which is good that I can do it, but is not as good as linking the car to the gateway and just using the excess.
I have an obsessive, and probably unhealthy, need to understand what's going on. So I'm concerned about another discrepancy: The daily totals shown on the Tesla app and the Solar Edge web site are vastly different. For example, as of 4:30 p.m. today, Solar Edge says that I have produced and consumed about 30 kWh. The Tesla app says that I've produced 15 kWh and consumed 14.2 kWh.
None of this really matters. What really matters is that I'm not drawing power from the grid, which I can see on my electric meter. I can run the A/C and charge the car and everything else I do, and I'm not drawing enough to see on the electric meter. Maybe averaging 3 kWh/month right now. And I appear to have excess capacity for the hotter months coming up.
After the inspection my guy will be able to install a NEMA 14-50 in the garage for me. Right now the car cannot draw enough power to make use of all the power the panels can produce, so some of it gets buffered through the Powerwalls. It will be better once I can draw 3 1/2 kW (the limit I'll probably set it to) rather than the present 1 1/2.
None of this really matters. What really matters is that I'm not drawing power from the grid, which I can see on my electric meter. I can run the A/C and charge the car and everything else I do, and I'm not drawing enough to see on the electric meter. Maybe averaging 3 kWh/month right now. And I appear to have excess capacity for the hotter months coming up.
After the inspection my guy will be able to install a NEMA 14-50 in the garage for me. Right now the car cannot draw enough power to make use of all the power the panels can produce, so some of it gets buffered through the Powerwalls. It will be better once I can draw 3 1/2 kW (the limit I'll probably set it to) rather than the present 1 1/2.
I checked my electric bill for June, before the solar was installed. My average daily usage was 30 kWh. So the Tesla app is totally bat-*sugar* as far as daily totals. The only question remaining is whether the real-time power flow numbers are reliable.
The generation figures shown by the Tesla app and the SolarEdge portal should not be that different. Bring this to your installer's attention and see if he can find the reason. It may be a configuration or measurement problem. If you have more than one inverter, the Solar CTs may only be measuring one of them.
The totals should not be off that much.
It is very common for the CT’s to be set up incorrectly. There are solar edge site CT’s, Tesla site CT’s and Tesla solar CT’s. Each has to be on the right phase and pointing the right direction. Lots of variables and if anything is wrong you’ll see weird stuff.
Smart export has value because it allows you to export from 9-4 with no credit and you do get credit for any export from the Pv after 4. It also saves from needing the 400 dollar solar edge monitor and CT’s. And the Pv produces when the grid goes down. So it’s better than css but they don’t like selling it because it’s either not understood or they don’t like the longer approval process than CSS. Yes some circuits are getting full for zero export but I believe most Maui installers are still getting cgs or smart export approvals. Safe bet is get the css closed out and then ask to apply for smart export.
I guarantee that a zero export system that’s set up properly won’t produce when the grid goes down. So either something is not right or the breaker you are turning off isn’t the main for everything and doesn’t accurately demonstrate an outage. Your installer can ask solar edge or Tesla rep and they will admit it’s a known issue that’s being worked on.
It is very common for the CT’s to be set up incorrectly. There are solar edge site CT’s, Tesla site CT’s and Tesla solar CT’s. Each has to be on the right phase and pointing the right direction. Lots of variables and if anything is wrong you’ll see weird stuff.
Smart export has value because it allows you to export from 9-4 with no credit and you do get credit for any export from the Pv after 4. It also saves from needing the 400 dollar solar edge monitor and CT’s. And the Pv produces when the grid goes down. So it’s better than css but they don’t like selling it because it’s either not understood or they don’t like the longer approval process than CSS. Yes some circuits are getting full for zero export but I believe most Maui installers are still getting cgs or smart export approvals. Safe bet is get the css closed out and then ask to apply for smart export.
I guarantee that a zero export system that’s set up properly won’t produce when the grid goes down. So either something is not right or the breaker you are turning off isn’t the main for everything and doesn’t accurately demonstrate an outage. Your installer can ask solar edge or Tesla rep and they will admit it’s a known issue that’s being worked on.
Thanks. I did show it to him. His answer is that Tesla does continual approximation all day, resulting in completely unreliable daily totals. He says the Solar Edge numbers should be correct. In support of this is the fact that the Solar Edge numbers match for production and consumption, and are consistent with my average daily usage for last month from my utility bill, and that Tesla's numbers for production do not match their numbers for consumption. I think Tesla's Power Flow numbers are probably good, since I can see these change in ways that make sense when things turn on and off, but however Tesla is determining daily totals is haywire.
I would never be exporting any power after 4 p.m. because my panels are not producing much by then. And we've demonstrated that the panels do produce when the grid goes down. There's a main breaker right next to the electric meter clearly labeled as the main shut-off. And when we shut that off the Tesla app showed that the grid was off and the system was on backup. Once the Powerwall dropped to 96% SoC the five-minute count started and then the solar came back on.
The problem here is probably that I have not described my system properly, giving you the wrong impression of the setup. My system is not actually zero export. I occasionally see export of one or two hundred watts, and Solar Edge reports about 200 Wh per day export from the house and about 500 Wh export from the cottage. Apparently the cottage, with only one Powerwall is not as agile and both imports and exports a little more than the house does. The house also imports a little, typically the same amount as it exports. I'm confident that my contractor knows what he's doing.
Some days we charge a car or two directly via solar and we did have a long outage during the night where the Powerwalls were drained when the cars charged. We tweeted Elon in May and he replied within minutes confirming that better communication between the Powerwalls and vehicles will be coming in a future update!
As long as you can verify that the solar kW in the Tesla app power flow and the solar inverters themselves show the same instantaneous kW value, then the measurements are set up correctly. If it's just the totals, then don't worry about it.
That's great news. Thanks!
Yep. I'm not worried. I'm now taking my daily totals from Solar Edge and my running power flow from Tesla.
48 hours ago I wrote down my electric meter reading. Since then I've driven about 50 miles and charged the car back up, run the A/C to keep the house always comfortable, and used electricity in all the normal ways. My Powerwalls are at 100% (being that time of day: late afternoon after plenty of sunlight they're always full; they'll start drawing down when the sun gets a bit lower and the A/C draws more power than the panels are producing). The electric meter has not moved in 48 hours. I think I've actually used about half a kWh over the course of those two days.
That's the bottom line: I'm no longer paying for electricity. I have my own free-energy machine. I always wonder about the people who claim the government or Big Oil is preventing us from having free energy machines. The government is actually going to give me a tax break for buying my free-energy machine. Big Oil is probably not happy, and probably lobbies against the tax breaks for solar, but so far they're SOL because you can still get one and get the tax breaks.
That's the bottom line: I'm no longer paying for electricity. I have my own free-energy machine. I always wonder about the people who claim the government or Big Oil is preventing us from having free energy machines. The government is actually going to give me a tax break for buying my free-energy machine. Big Oil is probably not happy, and probably lobbies against the tax breaks for solar, but so far they're SOL because you can still get one and get the tax breaks.
So now that I know to use the Solar Edge web site or app for my daily totals, and just use the Tesla app for power flow and Powerwall SoC, everything is wonderful. I'm using around 33 to 44 kWh per day, and of that only a half or less of a kWh is coming from the grid. My Powerwalls are generally between 30% and 60% SoC in the morning before the sun comes up.
The cottage is using 20 to 23 kWh per day, but having only one Powerwall it's drawing a half to three-quarters of a kWh per day from the grid. That Powerwall drops lower by morning because my renter is away at work during the day and most of her electric usage, other than daytime A/C, is in the evening after sunset.
So the system is working great and my electric bills in future will just be the connection fee.
The cottage is using 20 to 23 kWh per day, but having only one Powerwall it's drawing a half to three-quarters of a kWh per day from the grid. That Powerwall drops lower by morning because my renter is away at work during the day and most of her electric usage, other than daytime A/C, is in the evening after sunset.
So the system is working great and my electric bills in future will just be the connection fee.
I would add that I've got an export meter on the output of my SolarEdge inverter and this gives total generation around 3% lower than SolarEdge's numbers. The CT for the PW is also on the AC side of the inverter. I've concluded that the SE total represents the DC production of the panels - the inverter is about 98% efficient near/at full load but the efficiency drops off at part load so expect the Tesla version of the solar output to be slightly lower than SolarEdge's version.
I don't understand a lot of that. But in my case the Tesla version of total solar production is WAY lower than the Solar Edge numbers. Like half to two-thirds. And the Solar Edge numbers are consistent with what I'd expect based on last month's electric bill (before my system was switched on).
I suspect (but don't actually know) that Solar Edge does not see the Powerwalls except as part of the house, so counts power into the PWs as power consumed by the house, and doesn't see power coming out of the PWs at all.
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