Is this the best it gets?

[Achilles]

Hi guys, I recently got my 11.8 Kw system online with 2 Powerwalls and after finally seeing it in action I have some questions. My house will come off the grid at about 7am or so. The solar will then proceed to run the house (with A/C cycling because I live in Arizona) and charge the Powerwalls and have them fully charged by, let's say...3pm. Then it will start sending power back to the grid until the sun gets low enough to alternate between draining the Powerwall slightly when A/C is on, to recharging Powerwall when A/C cuts out. Now it's 8pm when my electricity gets cheaper and my Tesla starts to charge. With car charging and A/C on, my house is drawing almost 17Kw. The Powerwalls are completely drained by 9-9:30pm! This is if I don't set a percentage to keep for backup. Is this how it's supposed to be right now? Obviously winter will make a big difference when the A/C isn't running but I just assumed these batteries would last longer than this. Can anyone let me know how they run their setup optimally (When to charge car, how much backup percentage to use, etc?)

Chris

 

[5yJeff]

Is your car set to charge through the Powerwall? It will drain the Powerwall very quickly.

 

[Achilles]

Is your car set to charge through the Powerwall? It will drain the Powerwall very quickly.

Well, it justs automatically uses Powerwall energy. The only way I know of changing that would be to set the app to backup only.

Chris

 

[cwied]

If you don't have time-based control, then the only way you can improve the behavior is to manually switch modes when the electricity gets cheaper. With time-based control, the Powerwall will only discharge when electricity is more expensive.

Before I got time-based control, I would set the backup reserve to 100% until peak rate started and then set it down to 40% during the peak rate period. At the end of the peak rate period, I would set it back to 100%.

See here for more information:
Time-Based Control | Tesla
Powerwall Modes of Operation with Solar

 

[Achilles]

If you don't have time-based control, then the only way you can improve the behavior is to manually switch modes when the electricity gets cheaper. With time-based control, the Powerwall will only discharge when electricity is more expensive.

Before I got time-based control, I would set the backup reserve to 100% until peak rate started and then set it down to 40% during the peak rate period. At the end of the peak rate period, I would set it back to 100%.

See here for more information:
Time-Based Control | Tesla
Powerwall Modes of Operation with Solar

Thank you for that answer. Since my peak rate is from 3pm-8pm the solar will cover most of it. Can I ask how you one gets time based control?

If you don't have time-based control, then the only way you can improve the behavior is to manually switch modes when the electricity gets cheaper. With time-based control, the Powerwall will only discharge when electricity is more expensive.

Before I got time-based control, I would set the backup reserve to 100% until peak rate started and then set it down to 40% during the peak rate period. At the end of the peak rate period, I would set it back to 100%.

See here for more information:
Time-Based Control | Tesla
Powerwall Modes of Operation with Solar

 

[cwied]

Time-based control is apparently being rolled out by region. California and Australia seem to have it so far. You might try asking Powerwall support to see if they can put you on the list for the feature. As with all of Tesla's new features, it's best to be patient when waiting for it.

 

[BJReplay]

Now it's 8pm when my electricity gets cheaper and my Tesla starts to charge. With car charging and A/C on, my house is drawing almost 17Kw.

Time based control would probably help, but, realistically, your car charging should have been on a separate circuit not seen by your powerwall; you already had cars set to charge from cheap grid power. It seems hit and miss whether you have an installer who realises this and one who doesn't. There's more than one poster with your complain "my cars drain my powerwall fast". And you end up spending 15% more (powerwall round trip losses) to charge your car / run your house.

 

[Achilles]

Time based control would probably help, but, realistically, your car charging should have been on a separate circuit not seen by your powerwall; you already had cars set to charge from cheap grid power. It seems hit and miss whether you have an installer who realises this and one who doesn't. There's more than one poster with your complain "my cars drain my powerwall fast". And you end up spending 15% more (powerwall round trip losses) to charge your car / run your house.

So I should manually put my walls in backup mode during the charging cycle and not let the car charge off the Powerwalls?

I've thought about charging my car at my shop during the day also where the power appears to be cheaper. Then I get home and the car would only need a minimal charge at night.

Chris

 

[cwied]

Time based control would probably help, but, realistically, your car charging should have been on a separate circuit not seen by your powerwall; you already had cars set to charge from cheap grid power. It seems hit and miss whether you have an installer who realises this and one who doesn't. There's more than one poster with your complain "my cars drain my powerwall fast". And you end up spending 15% more (powerwall round trip losses) to charge your car / run your house.

I actually have a different viewpoint. With TBC, the only reason the car would be charging from the Powerwall is if the rate is currently high. Charging from the grid in this case would cost more than charging from the Powerwall. Draining the Powerwalls in this case would actually save money.

I think the complaints about the cars draining the Powerwalls are mainly from those who don't have TBC yet. I think the main issue is that you need a much bigger battery system to do full self-consumption if you're going to charge a car after the sun goes down. You could move the car charger to a different circuit, but raising the backup reserve would come out to the same thing. The only difference is that the Tesla app would show a higher self-consumption percentage. You'd still be consuming the same amount from the grid either way.

 

[cwied]

So I should manually put my walls in backup mode during the charging cycle and not let the car charge off the Powerwalls?

If I were in your place, I would put the Powerwalls into backup mode at 8pm. Charging the car after 8pm would probably still be a little cheaper than charging before 8pm, but if you need to charge before 8pm, charging from the Powerwalls would still be a little cheaper than charging from the grid provided they didn't charge during the peak rate period.

Note that the Powerwalls only read settings from Tesla's server once an hour, so you probably would want to delay your charging until 8:30 or 9 pm if you're doing the manual switching. Once you have TBC, the change will happen exactly at 8pm, so you'll be able to start charging more promptly.

 

[Achilles]

If I were in your place, I would put the Powerwalls into backup mode at 8pm. Charging the car after 8pm would probably still be a little cheaper than charging before 8pm, but if you need to charge before 8pm, charging from the Powerwalls would still be a little cheaper than charging from the grid provided they didn't charge during the peak rate period.

Note that the Powerwalls only read settings from Tesla's server once an hour, so you probably would want to delay your charging until 8:30 or 9 pm if you're doing the manual switching. Once you have TBC, the change will happen exactly at 8pm, so you'll be able to start charging more promptly.

Ahhh, Thanks cwied. I wondered why it didnt respond immediately to a change.