Told my Powerwall won't charge off Solar

[jjrandorin]

@BGbreeder - The installer admitted to misunderstanding Tesla guidance and that they should have used 5kW per PW2, that's why they comp'd one. The panels being pole-mounted is irrelevant. Any inverter(s) capable of producing > 5kW per PW2 is likely to cause the GW to shut down the system during peak production which is what we saw happening. Cloud edge effect may be enough to cause it to happen even with less than ideal slopes. At least that's my understanding after having spent way more time on the issue than I wanted

What @BGbreeder is saying (which I also agree with), is that it is "Likely" that Teslas guidance on "7.6kW PV per powerwall" is a catch all recommendation because in general someone with 7.6kW of RATED solar is probably not generating more than 5kW of power for any length of time.

This would be due to the fact that Tesla itself does not do ground mounted solar, and their guidance is based on multiple roof planes, imperfect roof angles etc, not a ground mounted system that can be all faced in the best direction, at the optimal angle for the location.

Its my belief that your installer likely did not account for the fact that Teslas guidance includes they dont do ground mount systems, etc, and they (your installer) provided you incorrect guidance because of it, and decided to do the right thing and take care of you as a valued customer.

 

[zƬesla]

Unless you have < 5kW array or inverter, then I would think the potential for going over and a system shutdown is there. It may only happen once a year, but the engineer in me cringes at "probably not generating more than 5kW of power for any length of time."

 

[BGbreeder]

Unless you have < 5kW array or inverter, then I would think the potential for going over and a system shutdown is there. It may only happen once a year, but the engineer in me cringes at "probably not generating more than 5kW of power for any length of time."

I agree, though I would point out that the charging limit of the 5kW impact is only felt in the off grid use case, at which point some (many?) owners might, might, be willing to consider certain extra power management duties...But trying to thread a 5kW limit against 12kW of installed production would be very, very, complicated. I wouldn't want to do it.

All the best,

BG

 

[zƬesla]

I would point out that the charging limit of the 5kW impact is only felt in the off grid use case

Important point. Wanting the PWs primarily for outages (vs TOU shifting), having something that would work off solar in an outage situation was critical for us.

 

[BGbreeder]

Important point. Wanting the PWs primarily for outages (vs TOU shifting), having something that would work off solar in an outage situation was critical for us.

For us it was the reason. Over a fairly short period of time, the grid here went from great to...well, not so good. I think part of the issue is alsothat we use digital devices more than we did a decade ago, and we do more WFH, both of which men we are less inclined to light the kerosene lamps, and pull out an old book when the power goes out.

All the best,

BG

 

[Jay Gatsby]

My free Powerwall, from the referral program, is being installed this week; after five years of waiting!

We are installing at a home that has an existing, owned, 12kW solar array. The array is at least ten years old so I imagine it's degraded some and not really 12kW anymore.

Tesla called me and informed me that because of the size of my array, my Powerwall will not be able to charge off solar. It will be installed only to charge off the electrical grid.

The Tesla energy technical guy told me that to charge off solar, I would need another Powerwall and a new design, permits, etc.

I told them to proceed with the installation and I might add that later, knowing that it would cost me an additional installation fee. I want the "bird in the hand" after waiting this many years.

I'm not super familiar with the design of solar energy systems. Can someone explain why the solar can't just charge my PW to full and then send the additional energy to PGE net metering? I'm ok if some efficiency is wasted and not all the energy is captured while charging the PW because the inverter can't take advantage of the entire 12kW array.

12KW 10 years ago!!! You obviously have heaps of fantastic solar collection potential ! Panels are now 10x more efficient per Meter sq. Your solution then depends on your overall power use. Work out how much power you'd need for a week without sun. HEck with that much roof potential in the sun..you'll easy be covered for winter.. make it 2 weeks! Total that up and divide by 13.5KW ..say make it 10kW ( to be sure)... and tally how many PW's you'd need (if they never needed charging for two weeks). Remember they still get some charge.. even in the rain! Be brave and bold.. Just buy PW3... so no need for new invertors.. Go off grid. Panels are now cheap as chips. Rip out what you have.. Get some new 500Kw Jinko's and the appropriate number of PW3's and you'll be off grid for sure! How good is that?!

 

[h2ofun]

12KW 10 years ago!!! You obviously have heaps of fantastic solar collection potential ! Panels are now 10x more efficient per Meter sq. Your solution then depends on your overall power use. Work out how much power you'd need for a week without sun. HEck with that much roof potential in the sun..you'll easy be covered for winter.. make it 2 weeks! Total that up and divide by 13.5KW ..say make it 10kW ( to be sure)... and tally how many PW's you'd need (if they never needed charging for two weeks). Remember they still get some charge.. even in the rain! Be brave and bold.. Just buy PW3... so no need for new invertors.. Go off grid. Panels are now cheap as chips. Rip out what you have.. Get some new 500Kw Jinko's and the appropriate number of PW3's and you'll be off grid for sure! How good is that?!

No way in the winter if one has a 100% large electric house!

I have 90 panels, 30kw, but in the winter am lucky to make 30kwh in the day. ( I make 185kwh at best in a day spring)

I just got my Dec PGE bill. I exported NOTHING back to the grid, but I imported 1900kwh's!!!!! Keeping my house 72 is NOT cheap, and charging the EV. My bill for Dec was over 700 bucks.

So unless folks are totally electric, one has NO idea how this works!!!!

 

[buckets0fun]

The high level short answer is because you likely have too much solar energy generated at once for one powerwall to handle.

FWIW (which isnt much), If I were you there is no way I would accept an install of 1 powerwall "only connected to the electrical grid" when I had solar. You probably think. "I will just get another one later" and the cost of that will probably be waaaaayyyyy (way) more than you think its going to be.

You should take the free powerwall, buy a second, and have them installed so that it works properly. You should get some install credit for the free / referral one, so it will never (ever) be as cheap for you to install another powerwall along with the one you are getting as it will be right now.

This is by far the best advice you could heed.

If tesla seems to think it’ll only be 3k extra to change the system, expect it to double. Also your wiring and conduit routing will get funky. Not to mention if you’re looking to use this for backup, is the amount of power that one PW can output going to be enough for your hvac + other home loads?

Imagine if NEM3.0 changes and adding ESS punts you up to nem3. That’d be a bummmmer

 

[Jay Gatsby]

No way in the winter if one has a 100% large electric house!

I have 90 panels, 30kw, but in the winter am lucky to make 30kwh in the day. ( I make 185kwh at best in a day spring)

I just got my Dec PGE bill. I exported NOTHING back to the grid, but I imported 1900kwh's!!!!! Keeping my house 72 is NOT cheap, and charging the EV. My bill for Dec was over 700 bucks.

So unless folks are totally electric, one has NO idea how this works!!!!

LOl no disrespect dude 30kwhr a day should be more than enough to live off.. - you need to slash your energy consumption. Cheers

 

[buckets0fun]

LOl no disrespect dude 30kwhr a day should be more than enough to live off.. - you need to slash your energy consumption. Cheers

The average heat pump uses 3.5kW
A tesla model 3 dual motor has a ~7X kWh pack.

An all electric home uses MUCH more than 30kWh/day in the winter, let alone the summer.

Charging one EV a day I hit 100kWh, without home loads.

 

[h2ofun]

LOl no disrespect dude 30kwhr a day should be more than enough to live off.. - you need to slash your energy consumption. Cheers

Sorry, when one has a large house like me, with EV charging, 4 heat pumps, etc, you have no idea. This does not include the 35kwh about I am getting from my solar, so you can add this onto these numbers for my real daily usage

 

[h2ofun]

The average heat pump uses 3.5kW
A tesla model 3 dual motor has a ~7X kWh pack.

An all electric home uses MUCH more than 30kWh/day in the winter, let alone the summer.

Charging one EV a day I hit 100kWh, without home loads.

yep, some folks have no idea or data what a 100% large electric home with an EV uses!! And this is using like 35kwh for free from my solar, or it would be a lot more

 

[BGbreeder]

LOl no disrespect dude 30kwhr a day should be more than enough to live off.. - you need to slash your energy consumption. Cheers

The climate in Australia where most Aussies live is substantially different than most parts of the US, and more houses in the US have, and were designed for, full home climate control (heating and cooling). As others have pointed out, for many folks here, their daily consumption includes charging electric vehicles.

I don't disagree that that US homes could be generally redesigned and rebuilt with more insulation and improved glazing to achieve lower energy demands, but not inexpensively, though the same could be said for much of the Australian housing stock.

All the best,

BG

 

[Jay Gatsby]

The climate in Australia where most Aussies live is substantially different than most parts of the US, and more houses in the US have, and were designed for, full home climate control (heating and cooling). As others have pointed out, for many folks here, their daily consumption includes charging electric vehicles.

I don't disagree that that US homes could be generally redesigned and rebuilt with more insulation and improved glazing to achieve lower energy demands, but not inexpensively, though the same could be said for much of the Australian housing stock.

All the best,

BG

Sure. Agree. Climate control = opening/closing the windows! Come on over! (You know you want to!)

 

[BGbreeder]

Sure. Agree. Climate control = opening/closing the windows! Come on over! (You know you want to!)

Thanks mate. Got any prawns on the barbie tonight? A favorite place to visit of mine, actually.

It is a wonderful corner of the world for the most part. (Coober Pedy doesn't rank that high on my favorite locales list for some reason...) Also home to an animal that hasn't been seen in North American zoos since before WWII, the echnida.

Plus a bunch of wonderful people, of course.

All the best,

BG

 

[tls]

12KW 10 years ago!!! You obviously have heaps of fantastic solar collection potential ! Panels are now 10x more efficient per Meter sq.

This is objectively false. Depending on panel type, the increase in efficiency since 1995 (28 years ago) is about 2X.

Source: Efficiency of solar PV, then, now and future – Solar photovoltaic

 

[Jay Gatsby]

This is objectively false. Depending on panel type, the increase in efficiency since 1995 (28 years ago) is about 2X.
View attachment 1001917
Source: Efficiency of solar PV, then, now and future – Solar photovoltaic

Ok 2x then - 10X ...2X even... no matter...if he replaces them with way more efficient panels, at 2X....still will equal 24kw for the guy. On the same roof space! .. that is still a heck a lot of panels and solar generation for the person... point still stands! Just MO!

 

[buckets0fun]

Ok 2x then - 10X ...2X even... no matter...if he replaces them with way more efficient panels, at 2X....still will equal 24kw for the guy. On the same roof space! .. that is still a heck a lot of panels and solar generation for the person... point still stands! Just MO!

Ok, so we ditch perfectly working solar panels and then spend bucks on new ones? How much extra wattage do we gain from such an awesome idea? Does this area have NEM3.0? Does the removal not destroy anything due to careless installers?

Always interesting to hear opinions of those that have a few breaths worth of knowledge in a subject.

 

[tls]

Ok 2x then - 10X ...2X even... no matter...if he replaces them with way more efficient panels, at 2X....still will equal 24kw for the guy. On the same roof space! .. that is still a heck a lot of panels and solar generation for the person... point still stands! Just MO!

Did you actually look at the graph? There's at most a 25% increase in efficiency over the past 10 years.

 

[Jay Gatsby]

Not sure why all the negativity... anyway. Suns out pumpin'... It's the summer solstice in only a couple of hrs! Rock on Tesla!