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Tesla Powerwall & Grid Services

m3-pw2

Member
May 3, 2019
80
42
USA
I have recently subscribed to my utility grid services through Tesla where Tesla uses renewable energy stored in battery during peak hours. The incentive is based on average kWh used:

Incentives for home batteries are based on the average kilowatt (kW) used per event, averaged over the season.
But I have looked at Tesla API which provides historical data, and stumbled at this for one of the days last week:

'period': 'day', 'installation_time_zone': 'America/New_York', 'time_series': [{'timestamp': '2020-08-20T01:00:00-04:00', 'solar_energy_exported': 62240.605277817696, 'generator_energy_exported': 0, 'grid_energy_imported': 12591.912777781487, 'grid_services_energy_imported': 81.56046702025924, 'grid_services_energy_exported': 10982.20399170497, 'grid_energy_exported_from_solar': 21980.641008299426, 'grid_energy_exported_from_generator': 0, 'grid_energy_exported_from_battery': 10982.20399170497, 'battery_energy_exported': 17590, 'battery_energy_imported_from_grid': 81.56046702025924, 'battery_energy_imported_from_solar': 20238.43953297974, 'battery_energy_imported_from_generator': 0, 'consumer_energy_imported_from_grid': 12510.352310761227, 'consumer_energy_imported_from_solar': 20021.52473653853, 'consumer_energy_imported_from_battery': 6607.79600829503, 'consumer_energy_imported_from_generator': 0}]}​

Tesla app says Powerwall exported 17.5kWh that day and is confirmed above. But the 'grid_services_energy_exported' shows only 10.98kWh that day. Other days are lower depending on how much solar production happens at the time, and how much the house uses.

So it seems that Tesla is computing the net exported from the Powerwall to the grid (minus solar production and house use).

I guess the wording from the program is not clear on what "used" mean. But the estimate dollar amount on average is much lower than the gross amount used by Powerwalls.

For reference, this is the Connecticut incentive with Eversource. Battery Storage Demand Response
 

wjgjr

Active Member
May 11, 2020
1,223
959
Silver Spring, MD
I have recently subscribed to my utility grid services through Tesla where Tesla uses renewable energy stored in battery during peak hours. The incentive is based on average kWh used:

Incentives for home batteries are based on the average kilowatt (kW) used per event, averaged over the season.
But I have looked at Tesla API which provides historical data, and stumbled at this for one of the days last week:

'period': 'day', 'installation_time_zone': 'America/New_York', 'time_series': [{'timestamp': '2020-08-20T01:00:00-04:00', 'solar_energy_exported': 62240.605277817696, 'generator_energy_exported': 0, 'grid_energy_imported': 12591.912777781487, 'grid_services_energy_imported': 81.56046702025924, 'grid_services_energy_exported': 10982.20399170497, 'grid_energy_exported_from_solar': 21980.641008299426, 'grid_energy_exported_from_generator': 0, 'grid_energy_exported_from_battery': 10982.20399170497, 'battery_energy_exported': 17590, 'battery_energy_imported_from_grid': 81.56046702025924, 'battery_energy_imported_from_solar': 20238.43953297974, 'battery_energy_imported_from_generator': 0, 'consumer_energy_imported_from_grid': 12510.352310761227, 'consumer_energy_imported_from_solar': 20021.52473653853, 'consumer_energy_imported_from_battery': 6607.79600829503, 'consumer_energy_imported_from_generator': 0}]}​

Tesla app says Powerwall exported 17.5kWh that day and is confirmed above. But the 'grid_services_energy_exported' shows only 10.98kWh that day. Other days are lower depending on how much solar production happens at the time, and how much the house uses.

So it seems that Tesla is computing the net exported from the Powerwall to the grid (minus solar production and house use).

I guess the wording from the program is not clear on what "used" mean. But the estimate dollar amount on average is much lower than the gross amount used by Powerwalls.

For reference, this is the Connecticut incentive with Eversource. Battery Storage Demand Response
The difference between grid_energy_exported_from battery (10982) and battery_energy_exported (17590) is 6608, which matches consumer_energy_imported_from_battery. This suggests that some of your battery usage went to support your home load and not out to the grid. I am not sure why that is the case - I do not know your settings (but speculate below) - but I think it makes sense that you would only be credited for the 10.982 kWh since that is all that was exported.

Looking quickly at the program, it looks like each event lasts from 2-7 PM. On a sunny day, at 2:00 I would guess you would have enough solar to be a net generator of electricity, particularly when looking at your totals. However, by 7:00 these days, I expect solar would not be sufficient to handle your home load. In a typical setup, this would mean that it needs to be supplemented either by grid power or the PWs. Given the nature of the program, I assume this means you would need to power your home from the PWs if you also want to send any PW energy to the grid since it doesn't logically make sense to both be exporting and importing from the grid at the same time. I'm wondering if this might explain why 6.6 kWh of battery energy is shown going to your home. You could also check your history graphs/5-minute export data to verify whether the PWs are ever discharging outside the 2-7 PM range.
 

m3-pw2

Member
May 3, 2019
80
42
USA
The difference between grid_energy_exported_from battery (10982) and battery_energy_exported (17590) is 6608, which matches consumer_energy_imported_from_battery. This suggests that some of your battery usage went to support your home load and not out to the grid. I am not sure why that is the case - I do not know your settings (but speculate below) - but I think it makes sense that you would only be credited for the 10.982 kWh since that is all that was exported.

Looking quickly at the program, it looks like each event lasts from 2-7 PM. On a sunny day, at 2:00 I would guess you would have enough solar to be a net generator of electricity, particularly when looking at your totals. However, by 7:00 these days, I expect solar would not be sufficient to handle your home load. In a typical setup, this would mean that it needs to be supplemented either by grid power or the PWs. Given the nature of the program, I assume this means you would need to power your home from the PWs if you also want to send any PW energy to the grid since it doesn't logically make sense to both be exporting and importing from the grid at the same time. I'm wondering if this might explain why 6.6 kWh of battery energy is shown going to your home. You could also check your history graphs/5-minute export data to verify whether the PWs are ever discharging outside the 2-7 PM range.
The event starts at 4PM and ends at 7PM from Monday to Friday. They can start earlier, as early as 2PM but it can only last for 3 hours, so they usually try to time it. I think only one day it started at 3PM instead of 4PM.
As for consumption, right, the house was using the energy from Powerwall after the solar production went down, and A/Cs kicked in. If my Powerwalls were not generating the electricity, my house would have added additional demand on the grid, so even if my house is using the powerwalls, I am hoping that I will still get compensated for it. Below is the graph for that day:

IMG_9566.PNG
 

wjgjr

Active Member
May 11, 2020
1,223
959
Silver Spring, MD
The event starts at 4PM and ends at 7PM from Monday to Friday. They can start earlier, as early as 2PM but it can only last for 3 hours, so they usually try to time it. I think only one day it started at 3PM instead of 4PM.
As for consumption, right, the house was using the energy from Powerwall after the solar production went down, and A/Cs kicked in. If my Powerwalls were not generating the electricity, my house would have added additional demand on the grid, so even if my house is using the powerwalls, I am hoping that I will still get compensated for it. Below is the graph for that day:

View attachment 580594
Yeah - that all makes sense. I am guessing from the program's perspective, even though you are right that without PWs, you would be drawing more from the grid, they are only paying the incentive when you are effectively using the PWs as a mini-generator to add energy to the grid in excess of your own use. To them "used" probably means used by them to supply to customers in general. It is a bit interesting though, because I see your point that once your system stops exporting PW energy to the grid, there is really no incentive (unless it is in the terms and conditions somewhere or there are time of use rates) for you to keep depleting the PWs for home use - in fact it would probably be better to just use grid power at that point to save the efficiency loss and also keep a higher battery level in the case of an unexpected outage.
 

m3-pw2

Member
May 3, 2019
80
42
USA
Yeah - that all makes sense. I am guessing from the program's perspective, even though you are right that without PWs, you would be drawing more from the grid, they are only paying the incentive when you are effectively using the PWs as a mini-generator to add energy to the grid in excess of your own use. To them "used" probably means used by them to supply to customers in general. It is a bit interesting though, because I see your point that once your system stops exporting PW energy to the grid, there is really no incentive (unless it is in the terms and conditions somewhere or there are time of use rates) for you to keep depleting the PWs for home use - in fact it would probably be better to just use grid power at that point to save the efficiency loss and also keep a higher battery level in the case of an unexpected outage.
The fact that the Powerwalls are drained down to 24% Monday-Friday, the incentive needs to be strong enough to justify the risk of loosing power overnight. I guess I'll find out soon when I receive my first incentive, but was hoping someone would have an answer. I will make a decision then if it is worth staying in the program.
 

m3-pw2

Member
May 3, 2019
80
42
USA
I confirmed with Eversource (my utility company) that the incentive is based on energy exported from battery during the event, and not the netted export to the grid.
 

SolPowered

Member
Aug 25, 2020
18
1
Connecticut
I have recently subscribed to my utility grid services through Tesla

Did they actually say it was a requirement to go through Tesla to do this? This really seems like an automated process to draw energy as needed, so I'd much rather not hand off 20% of the program benefit to Tesla for not really seeing a benefit of it. I spoke to my project advisor the other day and he hadn't seen it before where the payment had gone to Tesla and then Tesla reimburses the owner, and he was going to look in to it further, but I haven't gotten an update from him yet.

I'm in CT with Eversource, and I'm wondering if Tesla or Eversource gave you a definitive answer that you had to go through Tesla to apply, and that the 20% was just going to be Tesla's.
 

wjgjr

Active Member
May 11, 2020
1,223
959
Silver Spring, MD
I confirmed with Eversource (my utility company) that the incentive is based on energy exported from battery during the event, and not the netted export to the grid.
Nice - glad they could answer your question and that it was the sensible thing to do. That seems like a great incentive to have available.
 

m3-pw2

Member
May 3, 2019
80
42
USA
Did they actually say it was a requirement to go through Tesla to do this?
The link I provided in my main post says that you can fill the application yourself and send it to Eversource directly. But, I don't know if this means you will take 100% of proceeds in this case, or Eversource would just forward the application to Tesla and you sign the agreement with Tesla. If you do give it a try, and it works, let me know!
 

SolPowered

Member
Aug 25, 2020
18
1
Connecticut
The link I provided in my main post says that you can fill the application yourself and send it to Eversource directly. But, I don't know if this means you will take 100% of proceeds in this case, or Eversource would just forward the application to Tesla and you sign the agreement with Tesla. If you do give it a try, and it works, let me know!

Actually just got an email back from Eversource saying that I can't sign up directly and must go through Tesla. So, I'm not sure why they provide that option if it's not actually usable.
 

miimura

Well-Known Member
Aug 21, 2013
6,272
5,905
Los Altos, CA
I have seen screen caps of the charting in the app showing a 5th bubble with "Grid Services". I wonder why there are people with Grid Services enabled but not shown in the app.
 

m3-pw2

Member
May 3, 2019
80
42
USA
Actually just got an email back from Eversource saying that I can't sign up directly and must go through Tesla. So, I'm not sure why they provide that option if it's not actually usable.
If I remember correctly, it used to say that you need to contact the vendor to sign up and this was added recently I think. So not sure what is going on. I found one new bit of information that I misunderstood about the incentive that I will post separately.
 

m3-pw2

Member
May 3, 2019
80
42
USA
Regarding Eversource incentive, I got another clarification, the performance is based on average power exported from the batteries. Initially I thought it was based on average energy but looking at the details, everything is expressed in kW and not kWh. Maybe the term "used" implied energy in my mind in this description: Incentives for home batteries are based on the average kilowatt (kW) used per event.
 

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