Strategies for Powerwalls and Utility Demand Plans

[miimura]

Are the lines that are going down signify that you are sending energy back to the grid?

Yes, when the gray area for the Grid goes below the zero line, power is being exported to the grid.

The Tesla chart is plotted in 5 minute intervals. If @DanAman has utility metering on 15 minute intervals, those little spikes back and forth probably won't register. However, the meter may have demand detection that is finer grained than the interval sums. The billing tariff should specify how they derive the demand value.

 

[DanAman]

Yes, when the gray area for the Grid goes below the zero line, power is being exported to the grid.

The Tesla chart is plotted in 5 minute intervals. If @DanAman has utility metering on 15 minute intervals, those little spikes back and forth probably won't register. However, the meter may have demand detection that is finer grained than the interval sums. The billing tariff should specify how they derive the demand value.

I think it's a 30 minute period. in self-consumption mode it was 0.033. The one day test of time based control, cost savings moved it to 0.386. That was just the AC running. I imagine it would have increased with the AC, oven, stove, and washer.

 

[Darwin]

I ended up writing a Powerwall app for the SmartThings hub that allows for monitoring and control of the Powerwall through SmartThings, and also allows you to fully leverage SmartThings to send mobile notifications and to command smart devices and Powerwall functions based on the current status of the Powerwall and other smart devices.

The app unfortunately requires your Tesla credentials since it communicates with the Tesla server instead of the gateway due to a combination of issues between the way SmartThings and the gateway currently deal with certificates. There was something similar out there for the Powerwall that communicated directly with the gateway a while ago, but it broke when Tesla added a self-signed certificate to the gateway web interface.

The app is available here: https://darwinsden.com/powerwall and could use a beta tester or two if anyone is interested and has a SmartThings hub. I've been running it for a week now without issue, but definitely use at your own risk until it gets a little more testing.

The most useful part of the app for me right now is that it can be configured in the preferences to send mobile alerts when the battery level approaches the reserve or a user-defined percentage limit.

The app should alleviate the need to install a separate energy meter to your main panel when using the SmartThings demand management program: The Demand Manager App for the SmartThings Hub - DarwinsDen.com, since SmartThings can now get all home usage and solar data from the Powerwall itself.

 

[Dan123]

I ended up writing a Powerwall app for the SmartThings hub that allows for monitoring and control of the Powerwall through SmartThings, and also allows you to fully leverage SmartThings to send mobile notifications and to command smart devices and Powerwall functions based on the current status of the Powerwall and other smart devices.

The app unfortunately requires your Tesla credentials since it communicates with the Tesla server instead of the gateway due to a combination of issues between the way SmartThings and the gateway currently deal with certificates. There was something similar out there for the Powerwall that communicated directly with the gateway a while ago, but it broke when Tesla added a self-signed certificate to the gateway web interface.

The app is available here: https://darwinsden.com/powerwall and could use a beta tester or two if anyone is interested and has a SmartThings hub. I've been running it for a week now without issue, but definitely use at your own risk until it gets a little more testing.

The most useful part of the app for me right now is that it can be configured in the preferences to send mobile alerts when the battery level approaches the reserve or a user-defined percentage limit.

The app should alleviate the need to install a separate energy meter to your main panel when using the SmartThings demand management program: The Demand Manager App for the SmartThings Hub - DarwinsDen.com, since SmartThings can now get all home usage and solar data from the Powerwall itself.

Amazing! Thank you!

We may be using different versions of SmartThings app. Mine doesn't have an option to add SmartApps.


Activate the Powerwall Manager Smart App from the SmartThings Mobile App

1. From the SmartThings mobile app on your phone or tablet device, select the Automation -> SmartApps tab
2. Scroll to the bottom and select “+Add a SmartApp”
3. Scroll to the bottom and select “My Apps”
4. Select “Tesla Powerwall Manager” from the list
5. Scroll through each of the setting options and menus and select “Save” when done. You can always go back and add/change your settings.
6. The Powerwall Manager is now operational and its status can be viewed from the Tesla Powerwall Device on the SmartThings mobile app “Things” tab.

 

[Dan123]

I downloaded the SmartThings Classic and it worked.

Question:
1. In Backup Mode it lets me set a reserve percentage that is different from 100%. Is that intentional? Is it actually going maintain 85% in backup mode?

 

[Darwin]

I downloaded the SmartThings Classic and it worked.

Question:
1. In Backup Mode it lets me set a reserve percentage that is different from 100%. Is that intentional? Is it actually going maintain 85% in backup mode?

Thanks for the feedback! I'll update the docs to note that this requires the classic app.

I'm guessing that the reserve percentage that is set through the API only applies to self-powered and advanced time control modes. The Tesla app may just present you with locked controls showing 100% reserve when your in backup mode regardless of what the API reserve percent is set to. I may be able to do something similar with the SmartThings mobile UI, although it's pretty restrictive.

Any suggestions for enhancements? Maybe options for more mobile alert notifications or some simple automations that can be chosen in the app preferences? I've thought about maybe allowing a schedule for putting the PW into back-up mode, so that it will automatically change to use time controls mode during the week and backup mode over the weekend. I'm not crazy about how the battery will still discharge over the weekend in time control mode, even though I have no shoulder or peak defined over the weekend.

 

[Dan123]

Thanks for the feedback! I'll update the docs to note that this requires the classic app.

I'm guessing that the reserve percentage that is set through the API only applies to self-powered and advanced time control modes. The Tesla app may just present you with locked controls showing 100% reserve when your in backup mode regardless of what the API reserve percent is set to. I may be able to do something similar with the SmartThings mobile UI, although it's pretty restrictive.

Any suggestions for enhancements? Maybe options for more mobile alert notifications or some simple automations that can be chosen in the app preferences? I've thought about maybe allowing a schedule for putting the PW into back-up mode, so that it will automatically change to use time controls mode during the week and backup mode over the weekend. I'm not crazy about how the battery will still discharge over the weekend in time control mode, even though I have no shoulder or peak defined over the weekend.

The current app doesn't allow two peaks during the day. I am not sure if that's possible through SmartThings to accomplish two peak periods per day.

 

[Darwin]

I am not sure if that's possible through SmartThings to accomplish two peak periods per day.

My utility has two peak periods per day in the winter, so that could be a nice addition. I was told by my (3rd party) installer that Tesla was planning on supporting more than one peak schedule per day, so it is possible that the gateway allows for it.

The API appears to support an array of schedules. My gateway returns 2 schedules - one for weekdays and one for weekends. I could see what happens if I command an array of 3 schedules instead of 2. At some point. If I get brave enough. What could go wrong?

 

[NuShrike]

My utility has two peak periods per day in the winter, so that could be a nice addition. I was told by my (3rd party) installer that Tesla was planning on supporting more than one peak schedule per day, so it is possible that the gateway allows for it.

The API appears to support an array of schedules. My gateway returns 2 schedules - one for weekdays and one for weekends. I could see what happens if I command an array of 3 schedules instead of 2. At some point. If I get brave enough. What could go wrong?

Already tried. Tesla's functionality is below disappointing.

 

[Darwin]

I've updated the SmartThings app to show 100% reserve in backup-mode, and also added an option to schedule mode changes (Backup, Self-Powered, Time-Based Control) on specified times and days.

I was fairly happy with the performance of Time-Based Control/Cost-Savings to manage my demand, but I'm still getting around 300-500W of max hourly demand daily during my 2pm-8pm peak period - even though my net grid usage is always zero or negative. I'm going to schedule Self-Powered mode to occur during my peak hours and see how well that works considering the latencies the PW has in applying mode changes. If I can eliminate .5kW of demand each month, that could save me nearly $100/yr in demand charges at my utility demand rates. It's not worth the effort for me to do manually, but it's worth a try with an auto-schedule.

 

[Rahul]

@Darwin how is your setup going so far now that we're almost out of summer here in AZ? I'm in APS territory. I've been referral awarded a Founder's PW2 but don't have solar. I'm debating whether it's worth installing ($2500) just to help with load shifting. My demand charge last month was 11.4 and at ~$17/kw that was $194 on my bill. If I can figure out how to reduce the demand charge then it will make a lot of sense. My biggest problem is 4 A/C units in my home. I wish there was a way for them to coordinate not all turning on at the same time regardless of going above desired temp for a few mins.

I'd be up for beta-testing your app.

 

[Chancellor32]

Summer is basically over and thanks to the PW and Darwin’s demand manager my highest demand charge has been .8kw or $6! Take that SRP lol.

 

[Darwin]

@Darwin how is your setup going so far now that we're almost out of summer here in AZ? I'm in APS territory.

Just as with @Chancellor32, the solar, PowerWall and Demand Manager software pretty much squashed all my SRP demand charges for the summer. My demand usage and charges for the summer months averaged around 0.3kW and less than $5 per month. I've never had an on-peak energy charge, only surplus. The best part is I don't fret over my thermostat setting and current demand as I used to.

You're certainly welcome to try the demand management software, but as you mentioned, the 4 A/C units will definitely be a challenge. I only have a single unit and the main focus of the demand manager is on controlling a single thermostat in response to a demand kW usage goal you can set in the software. I haven't put much thought into how the software could manage multiple units/thermostats, but am open to suggestions. It's possible to instantiate a unique instances of the demand software per AC unit, with each unit having it's own kW demand goal, but they wouldn't be coordinated together without a software change.

Unfortunately, I'm not sure that using just a single Powerwall is going to help you much with your demand situation with 4 A/C units, since you'll still experience a demand hit each day once your battery is depleted.

Maybe not ideal, but If you have smart thermostats for each unit, have you looked at pre-cooling and then programming set points for each themostat so that they effectively turn off in a round-robin style? (eg up thermostat 1 temporarily to 80F from 3-4pm, up thermostat 2 to 80F from 4-5pm, up thermostat 3 to 80F from 5-6pm...)

 

[Darwin]

My biggest problem is 4 A/C units in my home. I wish there was a way for them to coordinate not all turning on at the same time regardless of going above desired temp for a few mins.

I gave this a little thought and it wasn't that difficult to modify the Demand Manager app to support multiple thermostats/AC units. The logic isn't overly sophisticated, but now if the app needs to raise the set point of a thermostat to manage demand to meet you defined demand goal (and more than one thermostat is available), it will attempt to sequentially choose a different thermostat/unit than the one it turned off in the previous 30 or 60 minute demand cycle.

The rest of the logic remains the same, so the app should perform the same as it did before if you only have one thermostat/AC unit.

I've had several requests to support multiple thermostats, so I think this change will be useful even if you don't end up using the app. I'm still testing to make sure I didn't break any of the base functionality, but should have the updates available soon from the usual location: The Demand Manager App for the SmartThings Hub - DarwinsDen.com

 

[Chancellor32]

I gave this a little thought and it wasn't that difficult to modify the Demand Manager app to support multiple thermostats/AC units. The logic isn't overly sophisticated, but now if the app needs to raise the set point of a thermostat to manage demand to meet you defined demand goal (and more than one thermostat is available), it will attempt to sequentially choose a different thermostat/unit than the one it turned off in the previous 30 or 60 minute demand cycle.

The rest of the logic remains the same, so the app should perform the same as it did before if you only have one thermostat/AC unit.

I've had several requests to support multiple thermostats, so I think this change will be useful even if you don't end up using the app. I'm still testing to make sure I didn't break any of the base functionality, but should have the updates available soon from the usual location: The Demand Manager App for the SmartThings Hub - DarwinsDen.com

Impressive work!!

 

[jbbjbbjbb]

Has anyone with a solar powerwall ever seen a path to charging from grid? I too am on SRP, and the ideal scenario would be to charge powerwalls from grid overnight, and use it to shave demand during the day. A product manager has suggested that this capability may become present when the solar tax incentives go away.

From the utility connection documents, it looks like the backup gateway only manages the grid interconnect, and not the power flow between the powerwall and the solar panels. Since the powerwall could be connected to grid in a standalone arrangement, what is the interconnect device that limits charging to the solar array? Is this connection made in the inverter? What prevents the powerwall from being grid charged?

 

[power.saver]

Only the software in the gateway limits the powerwall from grid charging. During storm watch mode it allows grid charging, but not during normal operation.

 

[jbbjbbjbb]

It doesn't seem that challenging to build a control circuit to bypass the gateway and allow grid charging then, I'm surprised I haven't seen this done. Theoretically you could wire grid power around the gateway, and run it through an isolation transformer or something (we'd only need 30a, so something like a Charles 30a like you'd use on a boat would work). Then the grid would still be isolated when the grid is down, but you could feed the power into the Powerwall 2 input. Seems like given the value of grid charging the powerwall, but the artificial limitation of only charging from solar due to the solar incentives, that somebody would think this is worth $1k, and try it out.

 

[jbbjbbjbb]

Alternatively maybe the power input needs to happen as DC on the other side of the inverter to seem like solar power, and I suppose one could run a big honking AC to DC converter on a timer relay and take an efficiency hit of 10-20%, but that would add less than a penny still to low cost off peak power.

 

[Rahul]

I gave this a little thought and it wasn't that difficult to modify the Demand Manager app to support multiple thermostats/AC units. The logic isn't overly sophisticated, but now if the app needs to raise the set point of a thermostat to manage demand to meet you defined demand goal (and more than one thermostat is available), it will attempt to sequentially choose a different thermostat/unit than the one it turned off in the previous 30 or 60 minute demand cycle.

The rest of the logic remains the same, so the app should perform the same as it did before if you only have one thermostat/AC unit.

I've had several requests to support multiple thermostats, so I think this change will be useful even if you don't end up using the app. I'm still testing to make sure I didn't break any of the base functionality, but should have the updates available soon from the usual location: The Demand Manager App for the SmartThings Hub - DarwinsDen.com

This is awesome. So how exactly does the algorithm work? Assuming all 4 thermostats are set to 80 degrees and all 4 zones get to 81, does it just get Zone 1 down to 80, then shut it off, then turn on Zone 2 let it get to 80, etc?

I signed off on getting the Powerall 2. Hopefully even though I don't have solarc ombined with your Demand Manager App it'll still help me w/ my demand charges. So other than the Powerwall all I need is the SmartHub, correct?

https://www.amazon.com/gp/product/B...om-20&linkId=b41765b7d89fc48dba3772820362932c