Tesla Solar and Powerwall for a large home?

[blueinsofla]

Looking into the potential of going with Tesla Solar and Powerwall for large South Florida home, but am getting mixed messages on whether or not the 4 Powerwalls would be able to back-up most of my essential needs in the overnight dark hours during an FPL outage following a storm. I have 3 a/c units and know they consume a lot of juice upon start-up, so would the addition of "soft starts" help ease the load that is drawn? Most of the homes in my community have a conventional generator, but I'm trying to come up with an alternative as I would need a fairly large and expensive generator that would require ongoing maintenance and would be worthless to me other than during a power outage.

Tesla had originally proposed a 28.35kWh solar system with 2 powerwalls, but I have since requested additional powerwalls to be added since I know 2 would not be able to handle the job in the event of a grid outage. One of the other challenges I am faced with is that Tesla says their gateway has a 200A limitation, and I have 400A service, so I'm waiting for them to come up with ideas for a work-around to that.

Any and all insights are appreciated and welcome, but hoping to find someone who has a larger home with the Tesla system.

Thanks in advance!

 

[SSedan]

If you want to spend enough I am sure you can 100% run the house on solar and PWs during an outage but in practically terms I think you are going to have to leave some of the heavy loads disconnected when not grid connected.

If the power is down for 2-3 days do you really need all three AC units running and presumably a pool or something?

 

[Tam]

...Tesla says their gateway has a 200A limitation, and I have 400A service,..

That's disappointing to hear. 400A should be accommodated/planned/designed as people might have multiple EVs with no ICE and also only have all-electrical appliances and discontinue natural gas use (Berkeley, CA).

Does Tesla clarify that it can still work with your 400A panel but its system maximum capacity would be capped at 200A?

Or does that mean they will take the 400A out and replace it with 200A panel instead?

...grid outage...

Tesla has a calculator with and without solar for you:

Tesla Powerwall

The calculator might be too optimistic and maybe for new appliances.

It's best to look for kWh monthly usage from your utility bill.

For a simplistic example: If you use 100 kWh per day, then you'll need 7 powerwalls x 13.5kWh = 94.5 kWh for your whole day.

It helps if the solar panel can inject more energy at that time so you won't need all 7 powerwalls.

 

[judylynn1949]

How many sq ft are you talking about???

 

[Ampster]

I am sure there are various sub panels of 200 Amps or less that the gateway could be connected to. I also think that some probably have loads that are less critical than others. It would be hard to answer the OP's question without an overview of the loads and the arrangement of the subpanels. For that size project it would be worth getting some professional design input. The best investment in any renewable project is in energy conservation. Perhaps some of the compressors are nearing the end of their useful life and could be upgraded to inverter compressors which are more efficient.

 

[miimura]

There have been installations that can handle what the OP wants. Tesla doesn't officially support things like off-grid operation, but they have been done too. An experienced third party installer can probably set up a larger system beyond the specs of a single Backup Gateway. We discussed some of the theoretical possibilities in one of the Generator threads.

 

[judylynn1949]

There have been installations that can handle what the OP wants. Tesla doesn't officially support things like off-grid operation, but they have been done too. An experienced third party installer can probably set up a larger system beyond the specs of a single Backup Gateway. We discussed some of the theoretical possibilities in one of the Generator threads.

Which Generator Thread???

 

[miimura]

Which Generator Thread???

There are a couple. I think the one I was thinking of is the first one below.

Generator support

PowerWall 2 Interface with a Generator

 

[judylynn1949]

There are a couple. I think the one I was thinking of is the first one below.

Generator support

PowerWall 2 Interface with a Generator

Thank you

 

[Dan123]

Looking into the potential of going with Tesla Solar and Powerwall for large South Florida home, but am getting mixed messages on whether or not the 4 Powerwalls would be able to back-up most of my essential needs in the overnight dark hours during an FPL outage following a storm. I have 3 a/c units and know they consume a lot of juice upon start-up, so would the addition of "soft starts" help ease the load that is drawn? Most of the homes in my community have a conventional generator, but I'm trying to come up with an alternative as I would need a fairly large and expensive generator that would require ongoing maintenance and would be worthless to me other than during a power outage.

Tesla had originally proposed a 28.35kWh solar system with 2 powerwalls, but I have since requested additional powerwalls to be added since I know 2 would not be able to handle the job in the event of a grid outage. One of the other challenges I am faced with is that Tesla says their gateway has a 200A limitation, and I have 400A service, so I'm waiting for them to come up with ideas for a work-around to that.

Any and all insights are appreciated and welcome, but hoping to find someone who has a larger home with the Tesla system.

Thanks in advance!

You may have a 400 amp service, but are you actually using 400 amps? The service is often oversized. Someone has to look at your appliances and usage to determine what your real demand is.

In any event, it is possible to install a 400 amp panel, move some of the larger loads to the 400 amp panel (1-2 AC units, tankless water heater, EV charger, pool pump). Then you can have a 200 amp panel (your existing panel with a 200 amp breaker will work) for everything else, and the existing panel would have a 200amp breaker, and would be backed up by the Powerwall. So you can definitely have most of your loads backed up by 2 Powerwalls. If money is not an issue, then 3 or 4 Powerwalls will provide you with longer runtime and more cushion.

So the answer to your question, it should be possible to redo your electrical wiring to accommodate a 200amp gateway.

 

[Jigglypuff]

How many KWH are you using each month in summer?

 

[reddy]

How many kWh do you consume overnight on a warm night? That will help you know if you have enough capacity on the Powerwalls. I have 4 , and with 4 older AC units i can’t go overnight before they are depleted. I run them down to 15%.

Also, with 28kw of solar you will likely fill them very quickly and still export a lot to the grid. I thought my 18kw system was huge, yours will be enormous.

 

[Pale_Rider]

I’ve got a 23.4kw system and 3 powerwalls. That’s enough to run 2 ACs and my wall charger if I absolutely had to. They said, it’s not enough storage to make it through the summer nights without being prudent with out AC usage. During the summer we use around 100+kWh per day. I figured we’d need about 6 based in my dual to dawn usage to make it through without making any usage changes.

 

[Mike Swift]

Most AC condensing units are not that efficient. If they do not have inverter driven motors both on the fan and compressor, they are old technology. Upgrading these items before you add batteries will reduce the number of Powerwalls required. Another massive consumer of your electrical energy is electric water heating. Salespeople were trying to sell me a tankless water heater because it was 6% more efficient than the 50- gallon electric unit in my house that had failed. Doing research, I found that using a Nyle split heat pump both dropped my max load to 700 Watts from 4500 Watts and used one third the kWh!

 

[blueinsofla]

If you want to spend enough I am sure you can 100% run the house on solar and PWs during an outage but in practically terms I think you are going to have to leave some of the heavy loads disconnected when not grid connected.

If the power is down for 2-3 days do you really need all three AC units running and presumably a pool or something?

These are valid questions and at the heart of my confusion. I would certainly want to focus on having the ability to back-up the "essentials" such as our 3 a/c units (I don't think we would need all 3 running simultaneously) and certain appliances. I'm not too concerned about my pool equipment or other non-essential equipment. I'm just trying to figure out how long we could survive solely on the Powerwalls and solar panels when faced with our electric utility going "dark" following a major storm.

 

[blueinsofla]

That's disappointing to hear. 400A should be accommodated/planned/designed as people might have multiple EVs with no ICE and also only have all-electrical appliances and discontinue natural gas use (Berkeley, CA).

Does Tesla clarify that it can still work with your 400A panel but its system maximum capacity would be capped at 200A?

Or does that mean they will take the 400A out and replace it with 200A panel instead?



Tesla has a calculator with and without solar for you:

Tesla Powerwall

The calculator might be too optimistic and maybe for new appliances.

It's best to look for kWh monthly usage from your utility bill.

For a simplistic example: If you use 100 kWh per day, then you'll need 7 powerwalls x 13.5kWh = 94.5 kWh for your whole day.

It helps if the solar panel can inject more energy at that time so you won't need all 7 powerwalls.

Tesla Energy acknowledges that this 200A limitation with their gateway is something they are actively working to improve. Basically, they told me that I could only back-up one of my electrical panels due to this limitation. They proposed a workaround to have the utility install a second meter, so we could have two gateways each backing-up it's own 200A panel, but FPL told me "no can do."

I have used the calculator, and like you, believe it might be overly optimistic which is why I'm throwing out the lifeline here to get some real-world examples from others with the system.

 

[blueinsofla]

How many sq ft are you talking about???

6,200 sq ft under air

 

[blueinsofla]

I am sure there are various sub panels of 200 Amps or less that the gateway could be connected to. I also think that some probably have loads that are less critical than others. It would be hard to answer the OP's question without an overview of the loads and the arrangement of the subpanels. For that size project it would be worth getting some professional design input. The best investment in any renewable project is in energy conservation. Perhaps some of the compressors are nearing the end of their useful life and could be upgraded to inverter compressors which are more efficient.

Thanks - I have found one gentleman (on this forum, actually) who has been very helpful in assessing my current sub-panel arrangements. He suggested that I have my electrician re-work the sub-panels to create an essential loads panel. I proposed this to the Tesla Energy people and they were not convinced that this would solve my current dilemma.

I'm now working with a local solar company to see if they can offer a better perspective.

My home is not even 2 years old, so I assume all of my compressors are the latest and greatest technology, but perhaps they are not, so I will heed your advice and look more closely into that...thanks!

 

[blueinsofla]

There have been installations that can handle what the OP wants. Tesla doesn't officially support things like off-grid operation, but they have been done too. An experienced third party installer can probably set up a larger system beyond the specs of a single Backup Gateway. We discussed some of the theoretical possibilities in one of the Generator threads.

Thanks - glad to hear this and if you could post a link to that thread I would be grateful.

 

[blueinsofla]

How many kWh do you consume overnight on a warm night? That will help you know if you have enough capacity on the Powerwalls. I have 4 , and with 4 older AC units i can’t go overnight before they are depleted. I run them down to 15%.

Also, with 28kw of solar you will likely fill them very quickly and still export a lot to the grid. I thought my 18kw system was huge, yours will be enormous.

I just looked back over the past few days, and it appears the average consumption between 7PM and 7AM is around 7kWh