Time of Use Power Shifting for Powerwall 2

[dlieu]

yes, technically it runs in backup mode only. But you can artificially cause a backup event by throwing off the main switch (so called "off grid" mode).

Note that backup != TOU discharge in several ways (sort of speculation on my part, based on how solar+PW+grid works though):

(1) during backup (off grid), maximum discharge rate is limited to that of the PW, which may cause various things like condensing units that require significant startup current, fail to start, or local brown-out events, (is that the right term), flickering LED lights etc. I observe that a lot during POW backup discharge. In TOU/discharge phase you should not be limited to PW maximum rate, the grid will be able to fill in the peaks and jumps in power as a secondary source of energy.

(2) switching to backup (off grid) creates a significant disruption to load. I expect TOU discharge transition switch would be much smoother and far less apparent. E.g., i use powerline eithernet which gets downed by backup switch. I expect this to go away once TOU is used instead, for that very reason.

(3) I am not 100% sure, but i think TOU is currently not technically a part of "unlimited" warranty, unlike the backup is. I guess they may still change it once TOU is actually a thing.

(4) and of course, most importantly, backup doesn't have an automatic schedule. Havning to physically throw the main switch two times a day is such a nuisance.

 

[Valijean]

what else is new?

Its obviously a lot more complex than it appears to us mere users, must be a huge amount of code to offer parameters for charging windows...

 

[Valijean]

So, if I don't have solar (with no plans to get solar), and TOU shifting is not available, then does that mean the only thing the Powerwall can be used for is energy backups in case of blackouts (which I almost never get)?

Not in the UK - in the UK without solar its an energy monitor!!

 

[MIT_S60]

yes, technically it runs in backup mode only. But you can artificially cause a backup event by throwing off the main switch (so called "off grid" mode).

Note that backup != TOU discharge in several ways (sort of speculation on my part, based on how solar+PW+grid works though):

(1) during backup (off grid), maximum discharge rate is limited to that of the PW, which may cause various things like condensing units that require significant startup current, fail to start, or local brown-out events, (is that the right term), flickering LED lights etc. I observe that a lot during POW backup discharge. In TOU/discharge phase you should not be limited to PW maximum rate, the grid will be able to fill in the peaks and jumps in power as a secondary source of energy.

(2) switching to backup (off grid) creates a significant disruption to load. I expect TOU discharge transition switch would be much smoother and far less apparent. E.g., i use powerline eithernet which gets downed by backup switch. I expect this to go away once TOU is used instead, for that very reason.

(3) I am not 100% sure, but i think TOU is currently not technically a part of "unlimited" warranty, unlike the backup is. I guess they may still change it once TOU is actually a thing.

I'd probably be better off selling my referral powerwall (if it ever ships) seeing as it won't really benefit me much at all then.

 

[strider]

Well, your first post mentioned the "the goal of never pushing power back to the grid," so I was addressing that scenario. I would think that if your utility allows a solar interconnection with export, then they'd allow a solar plus battery interconnection with export, sure.

Cheers, Wayne

Thank you for helping me think through this. Still have a lot to learn. I agree with your statement above. So the question then is why PWs don't allow it? Is it truly just taking them this long to code or is there a regulatory reason?

 

[MP3Mike]

I'd probably be better off selling my referral powerwall (if it ever ships) seeing as it won't really benefit me much at all then.

You can't sell it. Though you might be able to get a credit to spend at Tesla.

 

[strider]

I'd probably be better off selling my referral powerwall (if it ever ships) seeing as it won't really benefit me much at all then.

Well, supposedly, TOU shifting will be available "shortly". Idk about SoCal but when I lived on PG&E territory, it would have been nice to fill a PW at off-peak and use it during peak. I'd wait to see how the software pans out.

 

[MIT_S60]

You can't sell it. Though you might be able to get a credit to spend at Tesla.

Even with TOU shifting it wouldn't be a huge benefit given my current electrical usage. I would have saved less than $30 last month by shifting 100% of my usage to super off peak. Selling it (or credit with Tesla) would probably be a better option for me, but it will be pretty sweet to have even if it's just to show it off!

 

[Louv]

Q: "What does 'shortly' mean?"
A: "The TOU feature will ship before a Tesla Roaster gets to Mars' Orbit. Probably."

 

[dlieu]

not today. Today everyone has gone to look for the center core, it seems.

 

[paulcw]

Q: "What does 'shortly' mean?"
A: "The TOU feature will ship before a Tesla Roaster gets to Mars' Orbit. Probably."

Mike Keen who lives in Dorset, UK, has posted in the TOGUK Facebook Group:
“Tesla UK have asked me to field test the long awaited PW2 firmware upgrade that will allow us to store E7/10 electrons as promised last July. Watch this space.”

 

[wiredmeyer]

Mike Keen who lives in Dorset, UK, has posted in the TOGUK Facebook Group:
“Tesla UK have asked me to field test the long awaited PW2 firmware upgrade that will allow us to store E7/10 electrons as promised last July. Watch this space.”

watching

 

[Valijean]

Has he actually got it yet, will believe it when he has! Trying not to be cynical about why they'd ask anyone to 'field test' something that i'd hoped they done themselves.

 

[Bigtanuki]

I'd probably be better off selling my referral powerwall (if it ever ships) seeing as it won't really benefit me much at all then.

I think one of the things most folks don't realize is the badly Balkanized state of energy regulation at the state levels. Every state has different rules (and lobbyists affecting them) for things like NEM and TOU rates. California utility PG&E has clearly been successful based on their NEM 1.0 which buys power at about 3 to 4 cents/kWh and sells it to us at anything from ~12 to ~48 cents/kWh. From reading here it seems some utilities in other states offer as much as retail rate for power purchased back from consumer solar.
While everyone's goal for Powerwall in their home energy scheme is unique one thing is undeniable. Having a backup source of power is pretty amazing. Since our install in August 2017 we've had 7 outages. Most very short but one 90 minutes long. The only way I knew about them was seeing them in the Tesla app log. In addition, as I am in the PG&E territory my goal has been to absolutely minimize how much power I sell back and to maximize my self consumption. In my 2017 NEM period I sold back more than 1.2 MWh of electricity. In the 6 months since our PW install I've sold back less than 170 kWh.
Everybody's needs are different but resting assured that my wife will never be sitting at home in the dark when the power goes out is priceless.

 

[strider]

Well I just talked to my power company and if I install solar I have to switch to the non-TOU rate tariff. They do met metering but it's purely on kWh from the grid minus kWh to the grid net'd each month. No selling in any way. If your energy use is negative for the month you lose the kWh. I could not get solar and get PWs for TOU shifting. Peak here is 14:00-19:00 M-F, June-October inclusive. During that time power is $0.10/kWh, the rest of the time it is $0.02/kWh. On the non-TOU schedule we pay $0.04/kWh. I use ~26kWh during peak time so doing some super rough math it'll only save my $1.56/day or a little over $200/year. I would need 2 PWs for 26kWh at a cost of $13k or so installed, minus the federal tax credit yields about $9k. That nets me a payback in about 45 years Sure, there's some value to having a whole house UPS for outages but it's tough to put a price on that as outages are incredible rare here. I still need to put a pencil to solar in light of the above non-TOU rate but it seems that solar and/or PWs would be a vanity project rather than an economic one.

 

[SoundDaTrumpet]

Well I just talked to my power company and if I install solar I have to switch to the non-TOU rate tariff. They do met metering but it's purely on kWh from the grid minus kWh to the grid net'd each month. No selling in any way. If your energy use is negative for the month you lose the kWh. I could not get solar and get PWs for TOU shifting. Peak here is 14:00-19:00 M-F, June-October inclusive. During that time power is $0.10/kWh, the rest of the time it is $0.02/kWh. On the non-TOU schedule we pay $0.04/kWh. I use ~26kWh during peak time so doing some super rough math it'll only save my $1.56/day or a little over $200/year. I would need 2 PWs for 26kWh at a cost of $13k or so installed, minus the federal tax credit yields about $9k. That nets me a payback in about 45 years Sure, there's some value to having a whole house UPS for outages but it's tough to put a price on that as outages are incredible rare here. I still need to put a pencil to solar in light of the above non-TOU rate but it seems that solar and/or PWs would be a vanity project rather than an economic one.

Wow you get really great electrical rates in OK. Financial payback was a key criteria for me being in the Republic of California. I did pull the trigger for solar in '16 and PW soon in '18. I did consider a PW in '16 with PW 1 and glad I waited for PW 2. Net costs come to about the cost of a computer workstation. I did burn a lot of personal time to make this happen.

 

[dlieu]

[...]While everyone's goal for Powerwall in their home energy scheme is unique one thing is undeniable. Having a backup source of power is pretty amazing. Since our install in August 2017 we've had 7 outages. Most very short but one 90 minutes long. [...]

we in the hills have a cable ripped down in the canyon once or twice a year during winter storms. a power outage that lasts from ~6pm till next morning is not something we are unfamiliar with at all. Shorter interruptions are happening too.

 

[miimura]

I just got my two PowerWalls installed last week. It took 4 days to fully charge them from my 4.3kW solar system. Right now I am basically using one PW of capacity to ride through the Peak rate period and reserving the other for backup. In order to avoid running into the 50% reserve before 9pm, I am setting the system to Backup mode after 9pm or 11pm and setting it back to Self-Powered around lunchtime so that it is sure to be active by 2pm when Peak rates start.

This is what yesterday looked like. The light blue is the grid matching the household use when in Backup mode. Around 4pm you can see the solar + PW adding up to match the darker blue household use while the white line for the grid bounces around hugging the zero line.

My EVSEs are outside the gateway in my main panel, so their usage is not shown and the PWs make no attempt to offset their demand. For now, that is good because if I forget to put it to Backup mode the PWs would be quickly drained to the reserve level instead of just using the cheap EV rate overnight power.

 

[NuShrike]

In order to avoid running into the 50% reserve before 9pm, I am setting the system to Backup mode after 9pm or 11pm and setting it back to Self-Powered around lunchtime so that it is sure to be active by 2pm when Peak rates start.

Can you automate this like run a Raspberry Pi to call the PW API at the desired times of the day?

This would give us TOU-time-shifting without waiting for Tesla.

 

[miimura]

Can you automate this like run a Raspberry Pi to call the PW API at the desired times of the day?

This would give us TOU-time-shifting without waiting for Tesla.

I'm sure it is possible to automate it, but it's beyond my current knowledge. In fact, I would like to have my system upload to PVoutput.org but the Gateway is not on my local network. The tutorial I found needs to know the Gateway's IP so that it can connect and pull the data for uploading. If you were already connected for that purpose, it should be straight forward to get the Gateway to change modes.

Monitoring Tesla’s Powerwall2 on PVOutput.org