I talked to a Powerwall support rep today. One interesting fact that came out of the discussion is that they don't recommend TBC - Cost Saving mode for people with rate plans that don't have solar generation during Off-Peak. My Part-Peak starts at 7am weekdays, so she said that Cost Saving mode would not work for me and that I should just use Balanced mode. I have been doing that, but I found it interesting that there is no hint of this in the published information.
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Time-Based Control?
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Frankman60
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That is interesting. I wonder why Tesla would create a profile like Cost Saving when very few homes would generate solar energy during the Off Peak period, and therefore benefit from using the profile? To have solar production during off peak, the off peak period would need to extend well into the morning hours.
In the future, particularly during Spring, I expect that many utilities may be motivated by an abundance of solar energy to institute midday off peak rates. On the other hand, they probably don't want to miss out on being able to charge high rates to businesses with significant daytime energy use.
On the Weekend, Cost Saving works great because I have no Part-Peak (shoulder) rate at all. It jumps from Off-Peak to Peak from 3-7pm and then back to Off-Peak. So, really, they have to create the algorithms independent of any specific rate plan. However, they should do a better job of explaining what it is really doing and what kind of rate plan each mode is good for.
Somebody in one of the Tesla Energy Facebook groups said his rate plan has two Peak rate windows, one in the morning and one in the evening. So, the existing TBC scheme cannot accommodate his situation. That is the kind of thing they will have to improve to capture all the possible situations. Maybe choosing a Mode for weekdays and another for weekends should also be provided. While we're at it, how about a list of holidays when the rates follow the weekend schedule when the holiday falls on a weekday.
TBC activated a few days ago and really like it on the cost-control setting. NetMeter 1.0 and Grandfathered to program for another 1.5 years. Peak 12noon-6pm.
So setting to cost-controlled, during Peak hours, all house use is powered by PW2 until reserve setting (70% for me). At 6pm, cuts off and any remaining solar starts recharging the PW2 while grid supports the house. The following morning, solar charges PW2 until full and PW2 on standby until 12noon to start pk house support. DURING PEAK -- solar pushes entirely to the grid, maximizing the net metering.
The next piece I'd LOVE to have -- charge PW2 at night during super off-peak levels. This would be the most ideal in smart grid support. Full arbitrage (allowing consumer to discharge battery to grid during peak) is not good for anyone long term IMHO.
For those inquiring on TOU reasons -- NEM2.0 as TOU peaks in the evening. The reason is a lot solar and wind now in CA and duckbill phenomena has occurred with plenty of energy during the day and demand spikes in the evening now. This is where PW2 and load shifting performs the best and the intent of SGIP to save on peeker plants -- use batteries instead. In the past OhmAlerts regularly happened mid-day. The vast majority now is 6-7pm and 8-9pm when all the folk return home or hit upstairs. New solar installs all have TOU peaks in the evening now which makes PW2 a good thing to have.
Last wishlist -- Tesla allows car to plug into PW2 for additional house support in case PW2 battery is drained.
So setting to cost-controlled, during Peak hours, all house use is powered by PW2 until reserve setting (70% for me). At 6pm, cuts off and any remaining solar starts recharging the PW2 while grid supports the house. The following morning, solar charges PW2 until full and PW2 on standby until 12noon to start pk house support. DURING PEAK -- solar pushes entirely to the grid, maximizing the net metering.
The next piece I'd LOVE to have -- charge PW2 at night during super off-peak levels. This would be the most ideal in smart grid support. Full arbitrage (allowing consumer to discharge battery to grid during peak) is not good for anyone long term IMHO.
For those inquiring on TOU reasons -- NEM2.0 as TOU peaks in the evening. The reason is a lot solar and wind now in CA and duckbill phenomena has occurred with plenty of energy during the day and demand spikes in the evening now. This is where PW2 and load shifting performs the best and the intent of SGIP to save on peeker plants -- use batteries instead. In the past OhmAlerts regularly happened mid-day. The vast majority now is 6-7pm and 8-9pm when all the folk return home or hit upstairs. New solar installs all have TOU peaks in the evening now which makes PW2 a good thing to have.
Last wishlist -- Tesla allows car to plug into PW2 for additional house support in case PW2 battery is drained.
The first thought that popped into my mind was Tesla owners driving of to the nearest supercharger every day to fill up their car battery (for many owners, for free), drive home, and power their house.. for free.
Of course that's the foolishness of offering free supercharging in the first place. It makes no sense long term and they should have eliminated that long ago. I have no trouble paying for supercharging per use as we did with the Model 3 on the way back from LA last weekend.
It's silly folk buying a 80k-100k car waste their 30-60 minutes to dwell at a supercharger station to save a few dollars. [getting off soapbox]
Tesla could easily program that out -- saying the plug in is for occasional or emergency use and exclusive of free supercharging-- or whatever legal verbiage. They can easily ID the abusers of said program and cap them at x levels.
For the rest of folk, it makes logical, green sense to do that level of support -- and probably would sell even more 3 and Y cars for smart home leaning folk.
It's silly folk buying a 80k-100k car waste their 30-60 minutes to dwell at a supercharger station to save a few dollars. [getting off soapbox]
Tesla could easily program that out -- saying the plug in is for occasional or emergency use and exclusive of free supercharging-- or whatever legal verbiage. They can easily ID the abusers of said program and cap them at x levels.
For the rest of folk, it makes logical, green sense to do that level of support -- and probably would sell even more 3 and Y cars for smart home leaning folk.
There are probably other non-technical issues that they also would have to deal with, such as eligibility for the tax credit. Currently powerwalls don't charge from the grid in the US, but obviously cars do. The utilities might also not want people to use this as a loophole to arbitrage TOU rates.
True - But you're still time only time shifting the usage of power during peak. I don't see how utilities care if you time shift your energy from 12mn to 12n-6pm usage on your own (if you charge on their power and use on their power). Selling it back on power you bought from them at cheap (full arbitrage) is wrong. Right now, with TBC - Solar - we're optimizing generation to sell back at pk hours as a small scale generator. TBC-NonSolar is partial arbitrage already -- charge at night, use during pk hours. What's the difference with the car? (minus the free supercharger issue already mentioned).
I don't know for sure that they care, but they are obliged to honor grandfathered rate plans (and NEM 1.0, for that matter) that don't reflect the true cost of electricity. The current restrictions somewhat reduce the opportunity to arbitrage since you can only shift your solar production. Allowing the car to discharge during the day would essentially turn all the solar production to export, increasing both the arbitrage potential and transmission costs.
TBC Cost savings is that exactly already - I'm on NEM 1.0 for next 1.5 years. Pk 12noon-6pm -- sending all my solar to grid while my house is supported by the PW2. You can't DRAIN the batter to the grid--only to your house, so not true arbitrage.
Transmission costs are all local in our netmetering. Any energy we're sending to the grid is certainly used down the street and highly more efficient than coming from Escondido or other local peeker plants or even Lake Mead and elsewhere.
Transmission costs are all local in our netmetering. Any energy we're sending to the grid is certainly used down the street and highly more efficient than coming from Escondido or other local peeker plants or even Lake Mead and elsewhere.
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It is to a point, but you can only discharge what you charged from solar before noon. For me, most of the energy I get to discharge during full peak (1pm-7pm for me) comes from part-peak instead of off-peak. The PG&E EV rate makes it even more extreme, since all the off-peak hours are at night. If I could recharge overnight during the off-peak, PG&E would definitely have to pay me more.
Not directly related, re: the economics relating to arbitrage and whatnot...
When we think about "fair" and the ability and limitations re: arbitrage at the individual level, I think we may be missing a key point re: the economics of electric utilities. I'm not an expert and I may be entirely wrong about the following, but my understanding is that electric utilities are massively impacted when they cannot satisfy demand through their own generation and have to purchase supply on the open market. In particular, if/when these situations they can pay an order of magnitude or more for additional supply than it costs them to produce it on their own.
It feels to me like part of the equation here should be mechanisms to help us all collectively avoid such peaks...in this case, our interests align quite well with the utility because anything they do that increases their costs/decreases their profits will inevitably increase our costs.
The various opt-in programs that utilities now offer that allow them to reduce your demand are designed to help address that problem. But our batteries are doing the same thing -- twice over in fact, because not only does it allow us to sell solar capacity back during many of these peak periods but we're also lowering demand by drawing off battery at those times.
I think this is one reason why batteries are such an important part of the energy equation and why subsidizing them can make sense. It would be that much more amazing if we could have the batteries in our cars could integrate into the energy ecosystem like a power wall too.
Anyway, the point I'm trying to make is that maybe it isn't unreasonable for us to arbitrage...charge our walls at super-off-peak rates and provide it all back to the utility at peak rates...as long as we're willing to help them avoid the periods where they pay ridiculous rates for demand they cannot service on their own. Or at least it should be factored into the equation...we shouldn't just look at the individual economics, we need to look at the bigger picture.
When we think about "fair" and the ability and limitations re: arbitrage at the individual level, I think we may be missing a key point re: the economics of electric utilities. I'm not an expert and I may be entirely wrong about the following, but my understanding is that electric utilities are massively impacted when they cannot satisfy demand through their own generation and have to purchase supply on the open market. In particular, if/when these situations they can pay an order of magnitude or more for additional supply than it costs them to produce it on their own.
It feels to me like part of the equation here should be mechanisms to help us all collectively avoid such peaks...in this case, our interests align quite well with the utility because anything they do that increases their costs/decreases their profits will inevitably increase our costs.
The various opt-in programs that utilities now offer that allow them to reduce your demand are designed to help address that problem. But our batteries are doing the same thing -- twice over in fact, because not only does it allow us to sell solar capacity back during many of these peak periods but we're also lowering demand by drawing off battery at those times.
I think this is one reason why batteries are such an important part of the energy equation and why subsidizing them can make sense. It would be that much more amazing if we could have the batteries in our cars could integrate into the energy ecosystem like a power wall too.
Anyway, the point I'm trying to make is that maybe it isn't unreasonable for us to arbitrage...charge our walls at super-off-peak rates and provide it all back to the utility at peak rates...as long as we're willing to help them avoid the periods where they pay ridiculous rates for demand they cannot service on their own. Or at least it should be factored into the equation...we shouldn't just look at the individual economics, we need to look at the bigger picture.
You're completely correct that in the long run, the arbitrage will have a positive impact. The issue is that there are a lot of grandfathered customers who have deals that don't reflect the true cost of energy. I'm on a rate plan that has the peak period from 1pm to 7pm, which is now prime solar production time. If they let me arbitrage, I'd be making the current overproduction problem worse, not better. It seems like this is a case where regulations are preventing the utilities from being able to make best use of the technology.
In the long term Tesla will probably do the same here as in Australia and negotiate with the utilities to provide grid stabilization by aggregating the installed Powerwall base and using it to smooth out the peaks. There already is an opt-in for that. At that point I expect that they'll just pay the owners for use of their Powerwalls and remove all of the artificial gaming that we have to do now.
In the long term Tesla will probably do the same here as in Australia and negotiate with the utilities to provide grid stabilization by aggregating the installed Powerwall base and using it to smooth out the peaks. There already is an opt-in for that. At that point I expect that they'll just pay the owners for use of their Powerwalls and remove all of the artificial gaming that we have to do now.
We're already moving in the right direction with NEM 2.0. The TOU pk times are shifting correctly to 6p-9pm where all the demand has moved because off the nice solar we have. NEM 1.0 will disappear in 4 years with the 5 year Grandfather sunset. We have 1.5 years left on ours.
PW2 is nicely positioned for NEM2.0 folk to allow for TBC to minimize pk costs AND grid stabilization. I've always thought that allowing to charge at super off peak should be fine with NEM 2.0 schedule. Shifted support by any means is desirable for the utility; just not for us NEM 1.0 since our peak schedule doesn't help the utilities at this time.
PW2 is nicely positioned for NEM2.0 folk to allow for TBC to minimize pk costs AND grid stabilization. I've always thought that allowing to charge at super off peak should be fine with NEM 2.0 schedule. Shifted support by any means is desirable for the utility; just not for us NEM 1.0 since our peak schedule doesn't help the utilities at this time.
There are two parts to this. Your NEM 1.0 is good for 20 years from PTO for credits, but any grandfathered TOU periods have a 5 year sunset from PTO. So you will still be on NEM 1.0 for 20 years, but your grandfathered TOU periods will end by 2022 and then you'll be on the new TOU periods for the remainder. This applies to all investor owned utilities (SCE, PG&E, SDG&E) in California.
TOU periods are set forth in the Rate Schedule Tariffs while NEM 1.0 and NEM 2.0 have their own separate Tariffs. Historically, it seems to me that PG&E does not change TOU periods once a Rate Schedule is defined. When they wanted to define a new Schedule they created a new tariff and closed the old one. That has definitely happened for E-7, E-9, E-6.
SDGE: Time-of-Use Period Grandfathering for Net Energy Metering Customers | San Diego Gas & Electric ; - will be a sad day when out TOU shifts over. Still time to optimize out on the PW TBC --where cost savings pushes entire solar production to grid between 12n-6p for peak hours with the PW supporting house at that time.