What Factors does Cost Saving Mode Take into Consideration?

[MorrisonHiker]

I really am not worried about backup. Meaning we usually get warnings ahead of time if PGE is going to cut for wind and fire. Solar charges them back pretty fast. With 5, I have lots of capacity. I have a generator if they do go dead. Since my PW's are on 2 gateways, I really have 2 systems installed, so I at worst case can run an extension cord from one setup thats working to the dead part, if I want to. Everyone has a different reason they bought this stuff. I just am trying to not let it control me anymore than it already is. The longer I have it, the more I see I can just ignore, until something breaks like one of my inverters just did.

We had a derecho that came out of nowhere last year which knocked down all the power poles in my neighborhood so there was no Storm Watch to charge up the Powerwalls. Fortunately, we had enough reserve to make it through the night and our Powerwalls were able to charge back up and run everything for the rest of the 48 hour outage.

When we had our Powerwalls the first year, Storm Watch was new and would activate for high winds but not for blizzards! We tweeted Elon during that 48 hour outage and within hours, they turned Storm Watch on for blizzards. It didn't help us since the grid was out but it allowed those with Powerwalls to charge up if they still had grid power.

We don't have generators and wish our neighbor didn't since they ran constantly through both of those 48 hour outages. Very annoying as they are on the side of the house right outside my bedroom.

 

[h2ofun]

When I put the solar in I has on a tiered plan and sized it for $0 true up. I later got the Powerwalls through SGIP for backup but one of the conditions was I switch to the EV2a TOU plan. I didn't realize how drastic EV2a was and now need to use the Powerwalls during peak hours to still obtain a $0 true up.

I'm not concerned about leaving the Powerwalls at 100% and they get exercised daily anyway. But the 37.8MWh throughput rating tells me they are cycle limited so the less I use them the longer they should last.

Yea, I'll probably switch back to Cost Saving mode and play with the reserve/peak hours to target the $0 True-Up while maximizing winter reserve.

When the wife asked if the batteries would add complexity, I had to be honest and say yep. And the worst part is the having to be switched to the ev2-a plan. I can see this for EV's, but the batteries make no sense. I am going to try and upsize my solar to at least the suggestion of like 5kw per battery. I am way below that now. But being forced on ev2-a, yep with batteries, one needs to use 100% batteries at least during peak!!!! So what have you done, or will do, during the winter when our solar is about dead? And do you have any issues with doing the SGIP required cycling for the next 5 years?

 

[h2ofun]

We had a derecho that came out of nowhere last year which knocked down all the power poles in my neighborhood so there was no Storm Watch to charge up the Powerwalls. Fortunately, we had enough reserve to make it through the night and our Powerwalls were able to charge back up and run everything for the rest of the 48 hour outage.

When we had our Powerwalls the first year, Storm Watch was new and would activate for high winds but not for blizzards! We tweeted Elon during that 48 hour outage and within hours, they turned Storm Watch on for blizzards. It didn't help us since the grid was out but it allowed those with Powerwalls to charge up if they still had grid power.

We don't have generators and wish our neighbor didn't since they ran constantly through both of those 48 hour outages. Very annoying as they are on the side of the house right outside my bedroom.

Why anyone would run a generator at night is stupid!!!! I sure do not run mine. AND, I never run it all day long. Just a few hours morning, noon and night.

 

[RKCRLR]

When the wife asked if the batteries would add complexity, I had to be honest and say yep. And the worst part is the having to be switched to the ev2-a plan. I can see this for EV's, but the batteries make no sense. I am going to try and upsize my solar to at least the suggestion of like 5kw per battery. I am way below that now. But being forced on ev2-a, yep with batteries, one needs to use 100% batteries at least during peak!!!! So what have you done, or will do, during the winter when our solar is about dead? And do you have any issues with doing the SGIP required cycling for the next 5 years?

I have a generator but so far this winter I didn't need to run the generator once during outages. I currently have my reserve set at 50% (and I plan on increasing it) and even on partially cloudy days the Powerwalls get recharged. But there have been a lot of sunny days this winter which, hopefully for other reasons, is abnormal.

The SGIP cycling requirement equates to about an average of 15% discharge daily. I won't have any problem hitting that (wish I did have that problem).

 

[RKCRLR]

Why anyone would run a generator at night is stupid!!!! I sure do not run mine. AND, I never run it all day long. Just a few hours morning, noon and night.

A couple of my neighbors need to have medical equipment running during the night so they need to have the generators running all night. Luckily they are far enough away that I only hear them if the windows are open.

 

[MorrisonHiker]

Why anyone would run a generator at night is stupid!!!! I sure do not run mine. AND, I never run it all day long. Just a few hours morning, noon and night.

A couple of my neighbors need to have medical equipment running during the night so they need to have the generators running all night. Luckily they are far enough away that I only hear them if the windows are open.

Our neighbors with the generator have an indoor pool. I guess they just can't let those pool pumps stop running!

Our neighbor across the street just got solar and a single Powerwall so he'll be able to keep the lights on. Our other neighbor is considering solar. We ran an extension cord to her house and were able to keep her refrigerator and a couple other things running during the most recent 48 hour outage.

 

[jjrandorin]

When I put the solar in I has on a tiered plan and sized it for $0 true up. I later got the Powerwalls through SGIP for backup but one of the conditions was I switch to the EV2a TOU plan. I didn't realize how drastic EV2a was and now need to use the Powerwalls during peak hours to still obtain a $0 true up.

I'm not concerned about leaving the Powerwalls at 100% and they get exercised daily anyway. But the 37.8MWh throughput rating tells me they are cycle limited so the less I use them the longer they should last.

Yea, I'll probably switch back to Cost Saving mode and play with the reserve/peak hours to target the $0 True-Up while maximizing winter reserve.

That 37.8 MWh number is the warranty for grid charging them, not for charging them from solar. Since batteries are going to degrade anyway, to me, the worst possible outcome is to "baby" them and have them lose 20 something percent by 10 years. I would rather use the H*** out of them, and see if they actually degrade 30 percent before 10 years unlimited cycles which is our warranty when charged from solar.

To each their own, though, definitely.

 

[h2ofun]

A couple of my neighbors need to have medical equipment running during the night so they need to have the generators running all night. Luckily they are far enough away that I only hear them if the windows are open.

Those are folks that really need some type of batteries

 

[h2ofun]

That 37.8 MWh number is the warranty for grid charging them, not for charging them from solar. Since batteries are going to degrade anyway, to me, the worst possible outcome is to "baby" them and have them lose 20 something percent by 10 years. I would rather use the H*** out of them, and see if they actually degrade 30 percent before 10 years unlimited cycles which is our warranty when charged from solar.

To each their own, though, definitely.

I am with you. Lets see if I can get below 30% in less than 10 years and see if they replace them free. And by then, these type of batteries will be junk anyways.
How does now measure what capacity the batteries are at so we can see what amount they are dropping off over what time frame? Is anyone doing this and can provide their numbers?

 

[RKCRLR]

That 37.8 MWh number is the warranty for grid charging them, not for charging them from solar. Since batteries are going to degrade anyway, to me, the worst possible outcome is to "baby" them and have them lose 20 something percent by 10 years. I would rather use the H*** out of them, and see if they actually degrade 30 percent before 10 years unlimited cycles which is our warranty when charged from solar.

To each their own, though, definitely.

While I don't take the 37.8 MWh as gospel it is better than nothing. It may be half that or twice that, or the Powerwalls may turn into pumpkins at 10 years no matter what.

But the $0.03 per KWh that I'm given for excess generation at True-Up isn't worth putting more cycles on the Powerwalls if there is a chance they will last longer with less usage.

 

[RKCRLR]

Those are folks that really need some type of batteries

They are on fixed incomes and can't afford to do it themselves. Some of my neighbors can't afford the wildfire insurance rate increases and have stopped having insurance. They plan to walk away if the house burns down or put a gun to their heads if a fire is coming.

 

[h2ofun]

They are on fixed incomes and can't afford to do it themselves. Some of my neighbors can't afford the wildfire insurance rate increases and have stopped having insurance. They plan to walk away if the house burns down or put a gun to their heads if a fire is coming.

Ouch.

 

[getakey]

It seems to me that the cost of NBCs versus the roundtrip loss to/from PWs is just about a wash. I'm not concerned about NBCs. My first priority is having PWs for backup. Second priority is cost savings. I set my reserve accordingly and use Cost Savings mode

 

[RKCRLR]

That 37.8 MWh number is the warranty for grid charging them, not for charging them from solar. Since batteries are going to degrade anyway, to me, the worst possible outcome is to "baby" them and have them lose 20 something percent by 10 years. I would rather use the H*** out of them, and see if they actually degrade 30 percent before 10 years unlimited cycles which is our warranty when charged from solar.

To each their own, though, definitely.

This brings up another question.
Does the app know the amount of degradation and take that into account when it displays percentages?
I.e., if the Powerwalls have lost 20% capability and you set a 50% reserve, do you have 50% (of 80%) left or 30% (I'm assuming fully charged will always be 100%)?

 

[MorrisonHiker]

This brings up another question.
Does the app know the amount of degradation and take that into account when it displays percentages?
I.e., if the Powerwalls have lost 20% capability and you set a 50% reserve, do you have 50% (of 80%) left or 30% (I'm assuming fully charged will always be 100%)?

I think that's why they only display percentages instead of kWh. It's much harder for the average person to see degradation if all they ever see are percentages.

I assume any percentages are based on current capacity. So 100% of 4 new Powerwalls would be close to 53 kWh but after a few years, 100% might only be 50 kWh.

 

[wjgjr]

I think that's why they only display percentages instead of kWh. It's much harder for the average person to see degradation if all they ever see are percentages.

I assume any percentages are based on current capacity. So 100% of 4 new Powerwalls would be close to 53 kWh but after a few years, 100% might only be 50 kWh.

That is my impression as well, and the Tesla owners API does expose the current capacity of each PW, so it is possible to monitor degradation that way.

It is also worth noting for anybody doing the monitoring that the app displays a different percentage for the PW than the local API does - 10% on the API appears to be where the PWs shutdown, which equates to 5% on the app. Essentially, the app is hiding a 5% reserve.

 

[miimura]

I just switched to Balanced mode yesterday and things operated as expected. The Powerwalls discharged during peak hours and stopped discharging at midnight when I'm off peak.
However, this morning at 5am when the heat pump came on they started discharging again and are continuing to discharge even though I'm on off peak rates.
This is the exact opposite of what I want since I never want to be using the Powerwalls during off peak hours. It didn't do this in Cost Saving mode.
I'll leave it it Balanced mode for a while to see if it figures things out.

You really need to let Balanced mode run for a week or so before it settles in to optimal running. You can discourage early morning discharge by raising the Reserve at night before you go to bed and it's obvious that you will have enough energy to run through midnight. After the solar starts generating, you can drop the Reserve again. Normally I don't bother to change the Reserve often because my solar is small compared to my batteries and usage. I just change the Reserve seasonally. Since mid-March, I have been generating more than my 3pm-midnight usage, so I drop the Reserve to allow for any unusual usage. The system normally adjusts PW charging between all-solar and surplus-solar to reach 100% close to 3pm.

 

[h2ofun]

You really need to let Balanced mode run for a week or so before it settles in to optimal running. You can discourage early morning discharge by raising the Reserve at night before you go to bed and it's obvious that you will have enough energy to run through midnight. After the solar starts generating, you can drop the Reserve again. Normally I don't bother to change the Reserve often because my solar is small compared to my batteries and usage. I just change the Reserve seasonally. Since mid-March, I have been generating more than my 3pm-midnight usage, so I drop the Reserve to allow for any unusual usage. The system normally adjusts PW charging between all-solar and surplus-solar to reach 100% close to 3pm.

Mine at 10% reserve tries to get batteries to 100% about noon, then all solar back to grid

 

[RKCRLR]

You really need to let Balanced mode run for a week or so before it settles in to optimal running. You can discourage early morning discharge by raising the Reserve at night before you go to bed and it's obvious that you will have enough energy to run through midnight. After the solar starts generating, you can drop the Reserve again. Normally I don't bother to change the Reserve often because my solar is small compared to my batteries and usage. I just change the Reserve seasonally. Since mid-March, I have been generating more than my 3pm-midnight usage, so I drop the Reserve to allow for any unusual usage. The system normally adjusts PW charging between all-solar and surplus-solar to reach 100% close to 3pm.

Honestly, I don't see an advantage of Balanced over Cost Saving for my use. I always want to run from the grid or solar during off peak, and only run off the Powrwalls during peak and part peak as necessary to obtain a $0 True-Up.
Balanced has the advantage of prioritizing home use of solar of solar over recharging the Powerwalls in the mornings but then I'm just saving some NBCs.

Edit: Now that I think about it, I wouldn't even be saving on NBCs assuming the Powerwalls got fully charged prior to peak rates.

 

[miimura]

Honestly, I don't see an advantage of Balanced over Cost Saving for my use. I always want to run from the grid or solar during off peak, and only run off the Powrwalls during peak and part peak as necessary to obtain a $0 True-Up.
Balanced has the advantage of prioritizing home use of solar of solar over recharging the Powerwalls in the mornings but then I'm just saving some NBCs.

Edit: Now that I think about it, I wouldn't even be saving on NBCs assuming the Powerwalls got fully charged prior to peak rates.

Like I said, it depends on the relative size of your solar system, batteries, and Peak consumption. This is yesterday on my system. It is just about exactly what I want the system to do. It charges my car from Off-Peak grid power and charges the Powerwalls from solar. If it thinks there will be extra solar, it will only charge from surplus solar (above what the house is using) and sometimes changes its mind during the day. On this day, it reached 100% at 3:30 after the start of the Part-Peak period. If I was to change anything, I would completely disallow the discharge that happened from 7-8am and just wait to start charging the PWs until the solar exceeded the household consumption.