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TBC with Two Peak TOU periods

Chancellor32

Member
May 10, 2018
719
485
Queen Creek, AZ
Seems like you should be fine. I think I lean towards "overkill" usually, so that's just me. And the battery is where I did the overkill since that seems to be the harder thing for me to add later, but also avoiding peak charges, and prioritizing toward erring toward extra battery capacity are my top priorities. I feel like I have more control over battery capacity and doling out the usage, vs the control (or lack there of) that I have over solar production based on weather and such. So I'd rather build the buffer into the battery end of things and use production averaging (including weekend production) to size the solar. For instance, jumping to 6k system but with only two Powerwalls actually had a negative impact in terms of payback for me based on my usage patterns as compared to doubling the battery size from 25kWhrs to 50kWhrs, and sticking with a 4k pv system, given the my particular house and power usage needs. Having said that, I will add panels eventually regardless, just for my own peace of mind. Sorry for the preamble, so to your actual question...

So, when using pre-cooling during the worst of summer, I still end up using about 14-18kWhrs
during the 2-8 peak on these 105+ degree days, but with the 54kWhrs of battery I'll have more than enough to cover peak, and peak is primarily what I want to cover 100% no matter what. Our off-peak is so cheap it makes no sense to use up battery cycles to cover off-peak usage. If after the battery is full I'm fine with extra solar going back to grid but charging battery for use only during Peak coverage will always be the priority.

When we're hosting/entertaining during peak summer days (usually Fridays), I find we're closer to 20-22k (depending on how hot it is outside) of peak usage no matter how careful I try to be - the house simply has to be cooler with lots of people, and cooking going on, usually all the lights are on, a couple fountains are running, etc. Most of this type of stuff is only off peak usage otherwise. I have a "Peak" mode, and a "Party" modes configured on my home automation system. Peak mode aggressively turns all high watt items off, well really almost everything off, even if somebody turns them on during peak, my system turns them right back off. If my wife and I are both out of our home office, which happens once or twice a week during the day, then the house temp is allowed to rise, and on those days my 2-8pm peak usage is only about 10kWhrs, but that's usually only once or twice a week, and on those days we end up eating out together since we don't want to go home until we can cool the place down! Ha!, and we eat out a lot anyway since we both work and all the kids are out of the house. :)

In the winter, during the 5-9am and 9-5pm peak times (am/pm), we use 7-10kWhrs at most (usually between 400-900 watts per hour) because I don't have to run the AC at all with my house during those hours. Although if my wife turns on her hair dryer or straighter in the morning I might have 30 minutes that average 1500-2000 watts in there somewhere during the morning hours.

If anybody is curious about pre-cooling in the desert, I've been doing some dry runs and measuring my usage under different scenarios, because I can't have the house warm at all during summer since I work at home as does my wife, and we have clients at the house at times, so I end up pre-cooling around from 5 or 6am until 8am (hotter forecast days I start it at 5am). The house cools down faster when it's coolest outside. then I pre-cool again from 12:30-2pm (SRPs peak starts at 2pm). With the pre-cooling, when peak hours hit, because of the battery I'll be able to run the AC in the house for 30-40 minutes every hour (when it's 108-115) outside and we've found the house stays reasonably cool until 8pm, maybe gets up to 77-78 degrees by 8pm because 30-40 minutes of AC running each hour isn't quite enough to keep up so the inside temperature creeps up on average from starting at or near 70 degrees at 2pm up to about 78 worst case usually by 8pm. I know this sounds crazy, but I pre-cool to 69-70 degrees in the early am for 2-3 hours - cools the house slab and granite countertops tops very nicely, and quickly, during the cool morning hours and it seems to help the house feel cooler the rest of the day. When the temp outside during early hours is around 70-80degress outside vs 110-115 at peak afternoon, the air-condition works quickly when it's cool outside, and not so well once it gets above 108-110. I don't pre-cool again until the next days early hours.

Most importantly, with 54kwhr battery I should be able to cover "entertaining days", and/or make it through a couple cloudy days, or unexpected high peak usage days (usually Fridays when we have family and friends over as often as not). It will requiring charging all weekend probably to get back to 100% with only a 4k pv system, and during the worst of summer that may not be quite possible to get back all the way to 100 over the weekend - we'll see (if so I'll add more panels). If it seems like after Monday or Tuesday we're trending high on our battery usage during peak hours, then maybe I should be able to do minor rationing of power on for a day or so if needed and cut AC back to 25-30 minutes each hour vs closer to 45 minutes for a day or so - which again, I can do with a toggle on the home automation system. I'm not doing the demand averaging plan because the off-peak hourly usage charges are higher (almost what the non-solar ez3 plan rates are), so I calculated the best value for my $s to be insuring I use 0 watts during peak hours Monday-Friday no matter what. One bad day blows the bill for the whole month with SRPs aggressive demand plan, but the payoff is huge if I can zero the demand hours out, so I'm going a little overboard on the batteries for that reason. Also since for 6 months of the year I'll hardly exercise the battery I figure it will last a longer than for folks that fully cycle their battery(s) every day based on my experience with electric cars so far. I should only be fully fully cycling the battery the equivalent of 2-3 times per week, and only for about 12-14 weeks out of the year - plus have significant power outage backup when needed most of the time - but which is rarely needed around here to be perfectly honest. In 3 years of living here the powers maybe been out 2 times, an only once more than a few hours, the other time it was minutes.

Last bit of info and "theory" about the way I spec'd the system is in regard to lithium battery health. It's well established that topping off lithium batteries has implications in terms of degrading battery life expectancy more quickly (though still great compared to other chemistries). Fully cycling the battery (from empty to full) also has battery health implications. It's also well established that running the battery to the low end of it's capacity also has life expectancy implications for lithium batteries, but maybe not as much so as always topping them off. Final factor for me, is lithium batteries can be safely charged faster at the lower ends of their capacity with less impact to the health of the battery, therefore can better make use of the incoming solar charge when less than 65-70% full. For all these reasons, I've heavily tilted the design of the system at my house so that with each passing day over the course of a single week the battery is slightly "less full" than the day before so that I'm at most only topping the system off once a week on the weekend. Also, on any given day I'm should only normally (on average) cycling about 20-25 of the battery capacity, with every day that cycle being shifted ever more toward the middle to lower end of it's range (on average) where the battery would prefer to be for best wear and tear. Take that with a grain of salt but there is fairly extensive research to back these principles up, and this is one investment worth maximizing.

Installation day for me is Sept 11th!
How many PW’s did you order?! Did you order 4? I surely hope not because 2-3 of those are going to be wasted. If you have a 4kw system like me it only makes 20-25kw per day total. Meaning it would take 2-3 days to fill up those PW’s. Plus if you only use 25kw max during the 2-8pm why are you getting more than 1-2 PW’s? So confused lol
 

JayClark

Member
Aug 6, 2019
224
181
Arizona
How many PW’s did you order?! Did you order 4? I surely hope not because 2-3 of those are going to be wasted. If you have a 4kw system like me it only makes 20-25kw per day total. Meaning it would take 2-3 days to fill up those PW’s. Plus if you only use 25kw max during the 2-8pm why are you getting more than 1-2 PW’s? So confused lol

Yes 4 power walls. Maybe go back and read my posts a little slower, try to understand my goals for the system, maybe it will make more sense. If not, it's okay. Ideally I'd like to not have to ration from 2-8, and the numbers are what I can safely do with rationing, but if the battery and "refill time" can support more I'll probably use it. This is "knowing" it will indeed take the weekend to get the battery back to close to 100% - which I think I've said multiple times in multiple posts in this thread and explained why that's okay for me. What I'm doing is indeed a little bit of an experiment, and I'll add more solar later if I need it. Otherwise, I have quite a bit of experience with battery systems, and explain my theory in that regard at the end of my last post. I'm okay if you disagree with that approach or think it's silly. I'm old enough at this point I'm okay making my own mistakes after educating myself as much as possible. I've had people telling me the right way to to do thing my whole life, and have done okay going my own direction more often than not. I guess I'll see, and will report back on my little experiment. I'm not afraid to report back that I failed if that turns out to be the case - I think it will be interesting detail for this group. I learn more from the edge configurations than the standard.
 
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Chancellor32

Member
May 10, 2018
719
485
Queen Creek, AZ
Yes 4 power walls. Maybe go back and read my posts a little slower, try to understand my goals for the system, maybe it will make more sense. If not, it's okay. Ideally I'd like to not have to ration from 2-8, and the numbers are what I can safely do with rationing, but if the battery and "refill time" can support more I'll probably use it. This is "knowing" it will indeed take the weekend to get the battery back to close to 100% - which I think I've said multiple times in multiple posts in this thread and explained why that's okay for me. What I'm doing is indeed a little bit of an experiment, and I'll add more solar later if I need it. Otherwise, I have quite a bit of experience with battery systems, and explain my theory in that regard at the end of my last post. I'm okay if you disagree with that approach or think it's silly. I'm old enough at this point I'm okay making my own mistakes after educating myself as much as possible. I've had people telling me the right way to to do thing my whole life, and have done okay going my own direction more often than not. I guess I'll see, and will report back on my little experiment. I'm not afraid to report back that I failed - I think it will be interesting detail for this group. I learn more from the edge configurations than the standard.
lol calm down buddy I didn’t need to read it slower more so ready it all again because it’s been a bit since I read the beginning threads. Do what you want or think is best, at the end of the day that’s all we can do. I’ll share a little perspective since my system is already installed and running. 4kw and 1PW. Normally use 8-20kw during peak time. Since activating system I have yet to have anything higher than a .2kw demand charge and my peak usage is negative each day. Battery is fully charged by 2pm each day, software forces solar to charge it before 2pm while house is pulling from grid. I think you can accomplish what you want with 1-2PW and 4-8kw. Would you have any regrets if you bought 4PW’s and 2 of them sat full each day and never discharging because it wasn’t needed? Honestly curious.
 

JayClark

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Aug 6, 2019
224
181
Arizona
lol calm down buddy I didn’t need to read it slower more so ready it all again because it’s been a bit since I read the beginning threads. Do what you want or think is best, at the end of the day that’s all we can do. I’ll share a little perspective since my system is already installed and running. 4kw and 1PW. Normally use 8-20kw during peak time. Since activating system I have yet to have anything higher than a .2kw demand charge and my peak usage is negative each day. Battery is fully charged by 2pm each day, software forces solar to charge it before 2pm while house is pulling from grid. I think you can accomplish what you want with 1-2PW and 4-8kw. Would you have any regrets if you bought 4PW’s and 2 of them sat full each day and never discharging because it wasn’t needed? Honestly curious.

Ha! Good information about your system, and good question in regard to the PWs sitting at 100%. My goal would be to keep the packs on average closer to 20-80% of their charge/capacity range during the summer, never being fully charged, never being empty, and actually always slowly creeping toward less full each day, and then never getting full except on the weekends. That's the reason for only 4k pv system. This will extend the battery life significantly. And again, I may add more PV depending on how this all plays out, as I would eventually like to charge our electric cars off of sunlight, vs just off peak rates even if it doesn't make total financial sense, just out of principle.

The "knob" I can turn on my house/system if the batteries indeed end up sitting at 100% when I'm doing maximum pre-cooling and. maximizing peak rationing, is then to do less pre-cooling (so spending less on off-peak), and run the AC more during peak to be more comfortable through the whole day, but still zeroing out my peak usage (thus using more solar balanced & buffered by battery, and making my wife happier, and me more comfortable for that matter). All this to keep the battery system in the sweet spot of it's capacity range between 20% and 80% full, but always edging toward the lower end until the weekend. With a house that uses between 100-140kwhr during the three hottest months, I have a lot of knob I can turn here. I will definitely use less overall power by doing less pre-cooling until I'm maximizing the solar, and keeping the batteries in the sweet spot.

I truly don't want these batteries bouncing against 100% everyday, and I understand Tesla builds a small amount of headroom in the PWs for this very reason. These batteries, just like in a Tesla car, will literally last nearly twice as long if they are only cycled the equivalent of 2-3 times a week vs 5-7 times/week. Cycling daily is a normal usage pattern I'm guessing, but it's the worst way to use lithium batteries systems if you can avoid it. In one sense, I'm buying more batteries now, so I have to buy replacements less often, and keep my house more cool while doing it if I have the capacity. Maybe with the declining price of batteries this approach is not a great tradeoff vs just buying more later if prices really come down and if replacements are are needed earlier because of daily cycling - but it is the direction I chose.

My approach also has the side benefit of giving me a significant amount of reserve backup on any given day because as you say I should not be using the whole battery if I turn the setting knobs on my home to the most extreme pre-cooling and peak rationing mode, but I should have enough slack to play around with optimizing the balance between the two. Possibly as you say it's still overkill. That is the risk I've chosen, but still believe I can manage.

And to be totally honest, while I'm not a prepper, there is still a part of me that wants lots of backup, more than I reasonably need. Just because. More money than sense? Maybe. I like to experiment, and I'm sure I'm not done adding to the system.
 
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miimura

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Aug 21, 2013
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The only potential problem I see with a small solar and large battery installation is that the rules engine controlling charge and discharge in the Powerwall is not ideal for all situations.

In my installation, the vast majority of the 17 months that the system has been installed have been run in TBC Balanced mode. The only drawback to this mode is that when the battery is relatively full after a weekend that has Off-Peak solar generation, the system tends to discharge during Off-Peak on Monday mornings. Today is a good example.

2019-08-19.jpg


On the advice of others in this forum, I tried TBC Cost Saving mode. It doesn't do what I want during the shoulder Part-Peak periods. When it reaches a SOC that it thinks is sufficient for the upcoming Peak period, it simply stops charging and goes into Standby. Sometimes it changes its mind and starts and stops charging multiple times between 11am and 2pm. When it stops charging, it lets the surplus solar not consumed by the house go to the grid to earn NEM credits. The only bad thing about it is that if you have very uneven Peak usage, you could definitely fall short and hit the Reserve before the end of the Peak period. This is very disappointing when there was more than adequate solar generation to avoid that happening if it had just continued charging from solar during the shoulder period.

If you set the Powerwall rate periods for only Off-Peak and Peak, you probably won't have that issue and it likely won't discharge during Off-Peak either.
 
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JayClark

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Aug 6, 2019
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The only potential problem I see with a small solar and large battery installation is that the rules engine controlling charge and discharge in the Powerwall is not ideal for all situations.

...

If you set the Powerwall rate periods for only Off-Peak and Peak, you probably won't have that issue and it likely won't discharge during Off-Peak either.

Great information miimura. What you describe could definitely could throw a spanner into the works.

In the summer, the heaviest usage months I'll just be using Off-Peak and Peak - so from what I've been reading, and based on talking to others that mode should work fine in my situation.

It's the off-peak winter months, where there are two peak periods that will run head-long into the weaknesses of the PW that you mention, since in the winter we have two peak periods, separated by off-peak each day. (5-9am, and 9-5pm). It will be interesting to see what happens, since my house goes from using up to 140kWhrs max per day at times in the summer, to as little as 20kWhrs or less per day in winter. It's going to suck if winter is what bites me hard when that's the time I basically sip energy relative to the rest of the year.

Although somebody else from Arizona, in SRP territory like I am, mentioned that using balanced with only a single shoulder configured that starts with the first peak, and ends with the second peak actually works pretty well for him - possibly because the single shoulder includes the peaks and in-between time of the two peaks periods, which also happens to be when we have maximum solar through the middle of the day. But he didn't have the big battery configuration I will have, so that might still make it wonky. We'll see, I'll be sure to report back, even if it's embarrassing!
 
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Darwin

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Jan 12, 2018
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96
Phoenix, Az
In the summer, the heaviest usage months I'll just be using Off-Peak and Peak - so from what I've been reading, and based on talking to others that mode should work fine in my situation.

Yes, using just Off-Peak and Peak (no shoulders) can help with the odd off-peak discharge issues. The behavior in peak though can burn through the batteries pretty quickly by discharging to cover net home usage while you exporting excess solar back to the grid. As long as your calcs account for that peak period behavior and/or the PW correctly predicts your usage, it sounds like you may be in good shape. If you run into issues, you may find that using Off-Peak + Shoulder (no peak) instead will work, even with the off-peak discharge squirelliness.

I'm currently experimenting with bypassing the Powerwall Advanced Time Controls scheduling, and simply auto-scheduling PW mode changes through my Samsung SmartThings Hub. Scheduling the PW to backup mode during off-peak and then to self-consumption mode during peak hours has been working almost ideal for me for demand management with SRP peak hours - without all the oddities. The only draw-back so far is that it can take a couple of hours for the the Powerwall to change modes after being commanded.
 
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JayClark

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I'm currently experimenting with bypassing the Powerwall Advanced Time Controls scheduling, and simply auto-scheduling PW mode changes through my Samsung SmartThings Hub. Scheduling the PW to backup mode during off-peak and then to self-consumption mode during peak hours has been working almost ideal for me for demand management with SRP peak hours - without all the oddities. The only draw-back so far is that it can take a couple of hours for the the Powerwall to change modes after being commanded.

Oh nice! I'll have to check into that. That's how I control my home with custom & borrowed modules installed through the SmartThings developer API/site for things like controlling nest, and logging 5 minute power usage to a google sheet from an AEON power monitor that writes to a google sheet and charts usage and such. That's how I've done my detailed usage analysis.

It's been a while since I've had to change anything or poked around with my Smarthings configurations, and I hadn't seen that anybody had connected up directly to the Powerwalls, although guess it shouldn't surprise me since I think I've seen an Australian YouTuber some how talking to the Powerwall. Although I thought he was only reading battery/solar state and levels from the Gateway, and using that info to ramp his Tesla charger amperage up and down to match solar production. So I guess I thought he could only write/change the car charger, not control the Powerwall. Something new to investigate, any jump start links in that regard would be appreciated.

Update: Never mind... just re read your last sentence where you answered this! "Also, I guess my impression was that it took a while for config change in the Tesla app to replicate to the PW - so trying time things precisely was difficult. Are you able to write a config change directly to the powerwall and have it take effective immediately - without syncing through the cloud first I guess?"
 
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Darwin

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JayClark

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I couldn't find anything out there either for SmartThings Powerwall integration, so I ended up writing my own:

Tesla Powerwall Manager app for the SmartThings Hub - DarwinsDen.com

So far, it's been working pretty well. If only Tesla would update the PW software to allow you to immediately change modes on command...

Nice, I'll have to check that out. Thanks. Yeah, so that's a not ideal if there is up to a multi-hour delay before the PW actually acts on the command.
 

NuShrike

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Nov 13, 2017
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My app supplements using the local API, so there's no delay except for my polling period of 5 minutes.

Technically, one can have numerous periods just by automatically pushing a changed TBC schedule as needed. This could be scheduled via the owner-API as a phone-app for maximum flexibility.

However, my experience has been the PW doesn't like the TBC schedule changing often, and will ignore changes, even given > 30 minutes of notice. This is where I supplement and use the local-API to check and override.
 
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JayClark

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Arizona
I couldn't find anything out there either for SmartThings Powerwall integration, so I ended up writing my own:

Tesla Powerwall Manager app for the SmartThings Hub - DarwinsDen.com

So far, it's been working pretty well. If only Tesla would update the PW software to allow you to immediately change modes on command...

Great work on the Smarthings app, really good instructions, installed easily - now I just need my system installed which is scheduled for second week of September.
 

JayClark

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Aug 6, 2019
224
181
Arizona
I couldn't find anything out there either for SmartThings Powerwall integration, so I ended up writing my own:

Tesla Powerwall Manager app for the SmartThings Hub - DarwinsDen.com

So far, it's been working pretty well. If only Tesla would update the PW software to allow you to immediately change modes on command...

So I was poking around your Smartthings app page, and the function & capabilities notes you provide, and then thinking about this in regard to the Tesla App/Powerwall delay for config changes taking effect relative to the Arizona/SRP winter 5-9am and 5-9pm peak periods. Your app seems to provide a good scheduling option in winter even if there is a few hour delay for changes to take effect. Initially using the app to schedule a rule for a single peak period (no shoulder) from 5-9am via the app, and when the morning peak ends then immediately setting a new peak period via your app/ST rules for only 5-9pm, and then again when that period ends set it again for the morning period... and so on. Since there is an 8 hour gap between any two Peak periods there should generally be no concern of the next configured peak period being applied before that time rolls around, or can it at times take longer than 8 hours? Am I thinking about this the right way, or a way that is possible if only using the PW during true peak periods is the goal, and otherwise saving all PW capacity for black-out type scenarios.
 
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Darwin

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Jan 12, 2018
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96
Phoenix, Az
Your app seems to provide a good scheduling option in winter even if there is a few hour delay for changes to take effect. Initially using the app to schedule a rule for a single peak period (no shoulder) from 5-9am via the app, and when the morning peak ends then immediately setting a new peak period via your app/ST rules for only 5-9pm, and then again when that period ends set it again for the morning period... and so on.

Thanks for the feedback. The SmartThings app allows for scheduling mode changes and reserve % changes, but does not currently allow you to schedule different TBC peak/off-peak hours to be applied at certain times. It should be pretty simple to add this. I'll take a look.

I've personally never seen a commanded change to the Tesla cloud take over 2 hours to get applied to the Powerwall, so I've currenty scheduled all my PW changes 2.5 hours in advance. I'm currently scheduling a) Backup mode for the weekend (starts 8pm Friday), b) Self-Powered mode for SRP peak hours (starts 11:30 am weekdays). I schedule TBC with SRP peak hours (as a shoulder) 2.5 hours before the end of SRP peak (5:30pm) so that the PW stops discharging precisely at 8pm, so there's a brief period close to 8pm that I'm usually in a shoulder TBC period instead of Self-Powered. It's not a big deal, but every once in a while I'll see a 100-200W demand spike 7-8pm that probably wouldn't be there in self-powered. I'm guessing. I'm not aware of a way to know when the PW actually is acting on the commanded change to the Tesla cloud servers.

Since it sounds like you're using the AEON Home Energy Monitor and SmartThings, you may also get some use out of this Demand Manager smart app for SmartThings: The Demand Manager App for the SmartThings Hub - DarwinsDen.com

I wrote it to manage demand with Solar using the Aeon HEM (pre-Powerwall), but it's proven useful to manage demand with the Powerwall as well. This app can calculate and display real-time 30 minute or 60 minute demand using either the PW data or Aeon HEM data. In addition to tracking real-time demand and providing demand related mobile notifications, you can also have it control the thermosat or other devices based on demand triggers. It can also graph your current solar production on a HomeSeer WD200 wall switch and display indications on the wall switch or other plug in light when you are in a peak period or when your demand goal is being exceeded.
 
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JayClark

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Thanks for the feedback. The SmartThings app allows for scheduling mode changes and reserve % changes, but does not currently allow you to schedule different TBC peak/off-peak hours to be applied at certain times. It should be pretty simple to add this. I'll take a look.

I've personally never seen a commanded change to the Tesla cloud take over 2 hours to get applied to the Powerwall, so I've currenty scheduled all my PW changes 2.5 hours in advance. I'm currently scheduling a) Backup mode for the weekend (starts 8pm Friday), b) Self-Powered mode for SRP peak hours (starts 11:30 am weekdays). I schedule TBC with SRP peak hours (as a shoulder) 2.5 hours before the end of SRP peak (5:30pm) so that the PW stops discharging precisely at 8pm, so there's a brief period close to 8pm that I'm usually in a shoulder TBC period instead of Self-Powered. It's not a big deal, but every once in a while I'll see a 100-200W demand spike 7-8pm that probably wouldn't be there in self-powered. I'm guessing. I'm not aware of a way to know when the PW actually is acting on the commanded change to the Tesla cloud servers.

Since it sounds like you're using the AEON Home Energy Monitor and SmartThings, you may also get some use out of this Demand Manager smart app for SmartThings: The Demand Manager App for the SmartThings Hub - DarwinsDen.com

I wrote it to manage demand with Solar using the Aeon HEM (pre-Powerwall), but it's proven useful to manage demand with the Powerwall as well. This app can calculate and display real-time 30 minute or 60 minute demand using either the PW data or Aeon HEM data. In addition to tracking real-time demand and providing demand related mobile notifications, you can also have it control the thermosat or other devices based on demand triggers. It can also graph your current solar production on a HomeSeer WD200 wall switch and display indications on the wall switch or other plug in light when you are in a peak period or when your demand goal is being exceeded.

Thanks again for the information. I'll definitely take a look at the AEON app you've created. For the last 1-2 years I've been using a ST SmartApp to log my house energy usage and Nest Temps from around the house and from the AEON energy monitor to a google sheet every 5 minutes so I can play with optimizing the house power usage, and AC use, to make sure the solar/PW setup I purchase is matched well to how I can optimize power usage in my house.

I use it to sum up all day usage, but also into hourly (and 30 minute) increments and the numbers have matched SRPs next day usage information within half a percent after applying a slight (but consistent) adjustment factor to the 5 minute recordings. So I've been pretty impressed with the AEON energy monitor. But it's purely been used for analysis so far, and just text message alerts if house energy goes above certain levels during certain times of day.

It's also been useful for comparing comparable-temperature days, but with different pre-cooling strategies, and of course no-pre-cooling strategies, as I planned the size and type of system to implement, and compared cost scenarios for all the different scenarios.

I'll definitely check out your app for use with the AEON energy monitor. Good stuff!
 
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Darwin

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Jan 12, 2018
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My energy use summed up in the spreadsheet, and summed into hourly increments have matched SRPs next day usage information with half a percent after applying a slightly adjustment factor. So I've been pretty impressed with the AEON energy monitor.

One thing I noticed while writing the code to calculate the integrated average real-time demand that matches SRP numbers, is how much the actual demand calculation is skewed in SRP's favor (instead of using the absolute value of the simple 30 minute net usage calculation). In some cases it made a noticeable difference in my original PW/Solar cost benefit analysis where I originally didn't account for this. I know I mentioned this before, but with this feature, SRP actually disincentivizes providing power to the grid to help with demand, since it does absolutely nothing to help with your 30 minute demand charge (just your net usage charge).

This is a closely related, albeit slightly different and more subtle issue than SRP charging you a demand penalty, without a way for you to earn a demand credit at other times that you help ease utilty demand. I think both are pretty sneaky, disincentivize solar, hurt overall grid demand, and of course increase utility profits. Someday maybe achieving constant instantaneous zero demand without any surplus might be a goal for overall grid health, but I think we're decades away from that.
 
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JayClark

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181
Arizona
One thing I noticed while writing the code to calculate the integrated average real-time demand that matches SRP numbers, is how much the actual demand calculation is skewed in SRP's favor (instead of using the absolute value of the simple 30 minute net usage calculation). In some cases it made a noticeable difference in my original PW/Solar cost benefit analysis where I originally didn't account for this. I know I mentioned this before, but with this feature, SRP actually disincentivizes providing power to the grid to help with demand, since it does absolutely nothing to help with your 30 minute demand charge (just your net usage charge).

This is a closely related, albeit slightly different and more subtle issue than SRP charging you a demand penalty, without a way for you to earn a demand credit at other times that you help ease utilty demand. I think both are pretty sneaky, disincentivize solar, hurt overall grid demand, and of course increase utility profits. Someday maybe achieving constant instantaneous zero demand without any surplus might be a goal for overall grid health, but I think we're decades away from that.

Yes, all on point. It's very punitive, and seemingly senselessly so - the numbers did surprise me as I started apply the implications of the SRP solar generation plan to my actual usage scenarios summer & winter.

This is a bit esoteric, but just trying to understand how they may calculate some of these usage numbers since I'm not installed yet (scheduled for a couple weeks from now). For example, do you happen to know if SRP uses rigid on the hour, and half-hour periods (2pm, 2:30pm, 3pm, etc) for their calculations, or would they shift their calculation in the scenario where I use my ac for a solid, but only for 30 minutes (say at a 3kWhr run rate), but insure it straddles two 30 minutes periods, thus only running 15 minutes during each period. Does SRP then shift and say that I used 3kWhrs from 2:15-2:45 (for peak and 30 minute period usage calculations) and charge me as such, or would they see it as net 1.5kWhrs from 2-2:30, and net 1.5kWhrs from 2:30-3pm Ince it only actually ran 15 minutes during each 30 minute period? I'm simplifying here, assuming I use no other power than the AC just for the entire hour from 2-3pm.

I'm also assuming, what ever I actually use in net actual during a 30 minute period, they then double it to come up with a "hourly kWh" peak and such usage number for charging me, but for the given 30 minute period.
 

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