Sonus
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You should be able to get an hourly consumption from your utility provider website. Try it, they have years' worth of data stored.
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Powerwall with non Tesla solar?
- Thread starter BrettS
- Start date
Hey, wow, I didn’t know that data was available. In my case it only goes back to September of 2019, which is when they installed a smart meter here. Unfortunately the interface is absolutely horrendous and incredibly slow, but the data is there.
It looks like I can download all the data at once in one big XML file, but I’m not sure what I can use to process that XML file. Does anyone know of anything that could use it? Anything would be better than their interface.
Here’s my hourly usage for yesterday:
I’m trying to figure out what that spike at 2PM was. I don’t recall doing anything yesterday afternoon that would have had a large power draw like that. I guess it could have been the car. I haven’t driven anywhere, but it turns the charger on to top itself off periodically.
My heat pump is 2.5 tons, and according to the label the LRA number is 72.5, so that seems to indicate that two powerwalls might not be enough.
It depends on your Latitude. I am just north of San Francisco (38 degrees north) and I see my solar curve get to half of its capacity by 9:30 AM and drop down to the same point at 5:30 PM. That covers more than 90 percent of my daily production. It will get longer every day until the solstice.
1) Non-Tesla panels and inverters work fine with PW's. I have Sunpower panels, Enphase microinverters, and there's been no issue at all.
2) My installer was Tesla-certified. And I paid about $17k after tax credits for two PW's, in addition to my panels. If I was doing it over, I'd get locals to install the panels and then get Tesla to install PW's, based on the Tesla-quoted prices I've seen on this forum. Maybe I'd have Tesla do the whole thing -- even my local installers' use of satellite photos and a drone was adequate to design a properly fitting system.
3) You will probably need at least 3 PW's with a 15kw array. Above a certain level of solar production, you have to add additional batteries. Someone can correct me on the exact numbers, but the gist is that if each PW can receive or output 5.5kw, a 2-PW system can only handle solar input of 2x5.5 kw = 11kw. So if you have more than about 11 kw (again, this may not be the exact number) worth of panels, you need a 3rd PW to handle the incoming power when the grid is offline and power can only go to the batteries.
4) I'm in south Louisiana and your power bills sound pretty high. With solar and battery prices falling steadily, and insulation prices remaining relatively steady, you might be better served by upgrading your insulation now and going solar later. Unless your home is very efficient now, a dollar spent on insulation in Florida will get paid back before a dollar spent on solar. Do both if you can (I see you've got a Tesla car!) but see if you can lower those monthly usage numbers. If you buy solar first and insulate later, you might end up with too much solar.
2) My installer was Tesla-certified. And I paid about $17k after tax credits for two PW's, in addition to my panels. If I was doing it over, I'd get locals to install the panels and then get Tesla to install PW's, based on the Tesla-quoted prices I've seen on this forum. Maybe I'd have Tesla do the whole thing -- even my local installers' use of satellite photos and a drone was adequate to design a properly fitting system.
3) You will probably need at least 3 PW's with a 15kw array. Above a certain level of solar production, you have to add additional batteries. Someone can correct me on the exact numbers, but the gist is that if each PW can receive or output 5.5kw, a 2-PW system can only handle solar input of 2x5.5 kw = 11kw. So if you have more than about 11 kw (again, this may not be the exact number) worth of panels, you need a 3rd PW to handle the incoming power when the grid is offline and power can only go to the batteries.
4) I'm in south Louisiana and your power bills sound pretty high. With solar and battery prices falling steadily, and insulation prices remaining relatively steady, you might be better served by upgrading your insulation now and going solar later. Unless your home is very efficient now, a dollar spent on insulation in Florida will get paid back before a dollar spent on solar. Do both if you can (I see you've got a Tesla car!) but see if you can lower those monthly usage numbers. If you buy solar first and insulate later, you might end up with too much solar.
I always feel compelled to chime in because this conversation is important but is usually only at surface level
The Powerwall 2's inverter is rated for 5kW constant power, which is both input and output (https://www.tesla.com/sites/default.../Powerwall 2_AC_Datasheet_en_northamerica.pdf). Each Powerwall has it's own inverter so each one you add increases the maximum instantaneous power your system can provide to your home or consume to charge the batteries. During a grid outage if you draw more than the maximum or your solar is producing more than your Powerwalls can handle (net of consumption) the Powerwall will shut off the inverter to protect itself. This will cause disruption to your backup power and could potentially cause damage.
There are many ways to prevent this from happening.
1) Scale your Powerwalls to exceed the maximum actual power provided by your solar panels. PV systems have two ratings: the panel rating and inverter rating. Most residential systems have undersized inverters for their panels (sometimes called "clipping") due to the fact that in the majority of installations it is more economical to do so (Worried about clipping? Don't be. - AC Solar Warehouse). The theoretical maximum output of your system is the lesser of the panel rating and inverter rating. That's a good start but doesn't tell the whole picture and while you could base your Powerwall sizing on that number and be 100% covered it may still be overkill. We all know that in real life panels are in physically different places and oriented in different ways. As long as your actual maximum power does not exceed the Powerwall rating you're good.
2) Take advantage of your inverter's frequency power scaling. Many new PV inverters (and some old ones) are configurable to scale down production based on the grid frequency. SolarEdge inverters all it "P(F) Power Frequency" (https://www.solaredge.com/sites/default/files/application_note_power_control_configuration.pdf, page 6) and Enphase calls it "curtailment" or "ramp down" (https://enphase.com/sites/default/f...Considerations-AC-Coupling-Micros-Battery.pdf, page 6). Since the Powerwall will increase the power frequency during off grid operations to instruct the inverters how to behave you can match the Powerwall's frequency profile with your inverters to ensure that you never exceed the Powerwall limits. This is what I do for my 8.6kW PV system which just barely reaches the PV inverter rating of 6.6kW.
3) Split your PV inverter strings and shut one or more PV inverters off during an outage. This is the least palatable option but one that some have floated on this board for large PV systems that aren't looking to add many Powerwalls. With this configuration you're essentially reducing the size of the PV system during an off grid operation and could either use a specific breaker to take panels offline or wire the Powerwall so that a portion of the PV is on the grid side meaning it will shut off automatically during an outage due to anti-islanding protections.
I don't know the answers to any of your other questions, but I have Solar Edge panels and they work fine with my Powerwalls.
I originally wanted an all-Tesla installation because I've been so happy with both my Tesla cars. But Tesla does not install here, so I went with a local installer who was recommended to me by the realtor who found me my house. I was delighted I did because everything works great, the installer has provided 5-star service after the sale, and I've read bad things here on TMC about Tesla installers.
If you get a reliable installer, they'll know whether or not Powerwalls work with the panels they use, and what features will or will not work.
I am SOOOOOOOOOOOOOOOOOO happy I got solar + Powerwalls. My A/C will not start without grid power, but that's not critical here as it would be in some other places.
I’d like to get solar panels and powerwalls for my house. About a year ago I got a number of quotes for solar, including one from Tesla where they came out to my house to do a site survey, and came back with a custom system designed for my house. I really liked the Tesla quote and I was so close to pulling the trigger, but unfortunately some stuff came up unexpectedly at the time and it didn’t happen.
Those issues have been resolved and I’m ready to move forward with solar again. I’ve gotten new quotes on energy sage and from Tesla again, but Tesla has now moved to a cookie cutter one size fits all model and I’m just not getting warm fuzzy feelings from Tesla’s new quote. The system I was quoted last year was about 14kW and at the time, after the site survey, they told me that I couldn’t go any bigger because they couldn’t fit any more panels on my roof without putting panels on the section facing north north east. As I recall that was about 38 or 40 panels total.
But now, without looking at anything more than a google maps image they are telling me that they’ll have no problem putting 48 panels on my roof for a 15.12kW cookie cutter solar install. I asked what happens if they get here and discover that they won’t all fit and I was told “Oh, that’s no problem, if that happens we’ll just put some panels on the north north east side and your production might be a little less than we estimated. But don’t worry, you won’t have to pay any extra”.
Additionally, the quote from last year included power optimizers and the quote from this year does not. I do have a tree that provides some partial shading on my roof during certain times of the day, so I think the power optimizers would be beneficial.
So because of all that I like some of the third party quotes that I’ve gotten a lot better. They all seem to use micro inverters and can customize the system based on the size of my roof, rather than trying to shoehorn in a predetermined number of panels. However, I also really want to add powerwalls to the system and this is where things get complicated.
Some of the third party installers that have given me quotes are authorized to install powerwalls, but they are quoting prices that are much higher than Tesla. Tesla quoted four powerwalls to go with the 15kW solar system. The total installed cost of those four powerwalls was $22,100 before the tax incentives. The third party companies quoted $19,200 to install two powerwalls.
It looks like I do have an option to just get powerwalls from Tesla without the solar install, but that’s a little more expensive. It’s showing a cost of $27,100 for four powerwalls and the supporting hardware and also says that it doesn’t include ‘electrical upgrades’, so potentially the cost could be more in the end. Additionally, it’s my understanding that the powerwalls will only qualify for the federal tax incentive if they are installed with solar panels.
So after all that, I guess here are my questions...
-If I do go with non Tesla solar panels will they still integrate well with the powerwalls? Will I be missing any features?
-Is it worth going with the Tesla solar quote, even though it doesn’t seem like the best solar option, just to save a considerable amount of money on the powerwalls? $22,100 before tax incentives or $16,354 after the tax incentives seems like a great price for four powerwalls.
-Any other things that I should be thinking about here? I feel like I’m pretty well over my head with all of this.
Oh, and a couple of final notes, even the 15.12kW system will not meet 100% of my power demand. Among my air conditioner here in Florida, my Model S, a large fish tank, and a pool I average about 70kW a day in the winter and can go over 100kW a day in the summer. I actually went through and added up my power bills and I used a grand total of 33389kWh over all of 2019. Tesla is estimating an annual production of about 19368kWh.
Additionally, there is no time of use billing here, so the goal of the powerwalls would be simply for whole house backup in the event of a power outage. Ideally I would like to continue operating the house indefinitely in the event of an extended power failure - I lost power for more than 3 days after hurricane matthew. I realize that I’ll need to cut back my power consumption for that to happen, but I’d still like to be able to run my air conditioner and make sure the fish tank and fridge and other critical things have power.
Thanks for all of your thoughts
In my situation, I did not look at Powerwalls at the same time. I did multiple bids but Tesla was not willing to negotiate so I went with SolarDirect in Florida. They use Trina TallMax 340w panels. I did have a 45 panel, 15.3Kwh system installed and the company worked with whatever I needed as far as sizing. I initially had them quote 75% and 100% of my usage. Unfortunately, I threw in a variable as I switched from a Chevy Volt to an M3 about 5 months in so I was using more electricity. This size system put me around 95% which is not too bad. I also replaced my hot water heater with a hybrid hot water heater. I just signed a contract for two Powerwalls installed by SolarCity. The cost of the Powerwalls installed is $17083.50. Hope all works out for you.
Those are the same panels we have quoted for our job along with a SolarEdge w HDWave inverter and were told the wiring will adjust for shade and still send power to the system. We spent a good deal of time with our rep when we were investigating what products we were getting, so this while not an immediate concern for us, could mean we might have some shade play into our set up down the road so it was a concern we wanted to address and understand.
You might want to read the section on SolarEdge Inverters on this site. It's #2 on the their list and explains the use of DC optimizers: "Panel shading a problem? For complex roof profiles or installations with shading issues this would be the inverter of choice, however for smaller systems or strings with 6 panels or less micro inverters are better suited." Best Solar Inverters 2020 — Clean Energy Reviews
Had the shutdown not happened in our area when it did (right as we were about to start our work), we'd be in a better position to answer from actual experience using them. Soon...hopefully!
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