Anyone else here playing the 100% self powered game?

[NathanielHrnblwr]

When I ordered 2x PW late last year, being self powered was not something I considered. Charging the car at night would require grid usage anyway since 2x PW isn't going to charge the Model 3. My install was early March and after playing around with the PW's a week after install, I left them in self powered mode until I could decide how I wanted to handle charging the car. I did not expect the car to drain the PW's as I did not realize non backed up loads would still draw from the PW's and I was putting the PW's in backup mode while the car charged at night, then moving them back to self powered.

Then a week or two later, the stay at home orders were issued. Things shut down. The car did not need to be charged daily. The PW's stayed in self powered mode. When I got my first full cycle bill, it showed 0 usage from the grid. The unexpected self powered challenge began!

I'll top off the car during the day when solar is strong - something impossible during normal times as the car is not home during solar generation. Run appliances during the day instead of night when it'll pull from PW. Cloudy day? Oh no, will the PW get enough charge to get through the night? It's been a fun challenge to monitor energy usage and stay "off the grid". Now that it is warming up, it'll be more challenging to be 100% self powered. Solar and PW can run the A/C, but if both compressors run at the same time, it'll start pulling from the grid unless it's mid day. It was hot enough to run the A/C today but I toughed it out lol.

This all is silly considering with NEM 2.0 I pay $10 min/mo. whether I use $10 worth of power or not so it's fiscally prudent to use that power, but that "100" self powered" line in the app is like a goal.

 

[DrSmile]

Does 0 usage mean you never pulled any electricity from the grid or that your usage equals the amount of solar produced? I'm definitely doing the latter due to COVID (17.5 MWh produced for the year, 17 MWh used), if my wife and I were driving our Teslas more I'd probably have it a few MWh the other way... In terms of being able to run off grid totally, there is zero chance of that for me, I exported 11 MWh to the grid and pulled in 10.5 MWh, so almost 2/3 of my used power was when the solar was not producing energy.

I only use my 2 PWs for backup though, so I probably could get it down to 50% if I ran down the batteries every night. But with net metering here what would be the point? I'd be losing money on the inverting and storage losses.

 

[aesculus]

I did not expect the car to drain the PW's as I did not realize non backed up loads would still draw from the PW's and I was putting the PW's in backup mode while the car charged at night, then moving them back to self powered.

Huh? I cannot understand how non backed up circuits could drain the powerwalls. They are essentially isolated from the powerwalls.

Are you sure it's not the backed up loads that are draining your power? If not then you need to revisit where you charger breaker has been placed.

 

[power.saver]

Huh? I cannot understand how non backed up circuits could drain the powerwalls. They are essentially isolated from the powerwalls.

Are you sure it's not the backed up loads that are draining your power? If not then you need to revisit where you charger breaker has been placed.

Non backed-up loads will drain the PW when the grid is up if the CTs are upstream of them (e.g. at the meter). They will not when the grid is down though. The CTs can be relocated downstream of the non backed-up loads to prevent them from draining the PW even when the grid is up. It all depends on where the CTs are placed that determines if the PW offsets the non backed-up loads.

 

[aesculus]

Well the CT's are just an indicator. They cannot direct the load. And yes my grid CT's show my non backed up charger using energy, but nothing is coming from the PW.

The only way these loads can drain from the powerwall is that they are on the backside of the isolation circuit. If not then the grid would drain the powerwalls by itself no?

Here is my car charging at midnight for a few minutes. It is not backed up. Note the PW is not involved at all.

 

[jjrandorin]

Huh? I cannot understand how non backed up circuits could drain the powerwalls. They are essentially isolated from the powerwalls.

Are you sure it's not the backed up loads that are draining your power? If not then you need to revisit where you charger breaker has been placed.

Thats not true. Non backed up circuts can be monitored by the placement of the CTs, and I believe that is how tesla normally sets it up unless you specifically say " I dont want the ability to power those loads with the powerwall, even if the grid is up.

(My non backed up wall connector, the only thing still left in my main panel, will receive power from the powerwalls if the grid is up, and I dont specifically put it in backup mode.

As far as OP's question goes, I am playing the same game. I also normally run self powered, because I am not on a TOU plan, but also dont want to use my powerwalls to charge the car normally because my normal work commute is 20+ kw of energy daily. With the shelter in place, not driving into work much, so basically managing around town driving by charging during the day.

 

[jjrandorin]

Well the CT's are just an indicator. They cannot direct the load. And yes my grid CT's show my non backed up charger using energy, but nothing is coming from the PW.

The only way these loads can drain from the powerwall is that they are on the backside of the isolation circuit. If not then the grid would drain the powerwalls by itself no?

Here is my car charging at midnight for a few minutes. It is not backed up. Note the PW is not involved at all.

View attachment 560958

Thats just how your electrical system is setup. Its not correct to make a blanket statement that the powerwalls can not supply powers to non backed up loads, because they absolutely 1000000% can (as I mentioned mine is setup that way. Car is not backed up, so if I flip the main breaker I can not charge the car... however when connected to the grid it pulls from the powerwall.

In fact, I would imagine, if you swap from the advanced setting that you are likely in, into self powered, you would see the same powerwall usage. What I see looking at your graph, is that when you charge your car, your system diverts any leftover solar to the powerwalls (why the big spike in powerwalls receiving power when you are charging your car?)

 

[bkp_duke]

I'm in the Self-powered game as well. Started off with 3 PW2s just a little over 2 years ago. Since then we have been about 94% self-powered, according to the app.

Added a 4th PW2 this past week, so we'll see how much further up that brings us.

The biggest hurdle has always been those weeks in Dec - Feb where it rains for about a week straight. No matter how hard we try, seems we always get into the grid at that point. Considering adding 1-2 kw to the current solar system, if I can find some roof space for the panels.

Still, nice knowing that in a prolonged outage we can do pretty well.

 

[wjgjr]

Does 0 usage mean you never pulled any electricity from the grid or that your usage equals the amount of solar produced? I'm definitely doing the latter due to COVID (17.5 MWh produced for the year, 17 MWh used), if my wife and I were driving our Teslas more I'd probably have it a few MWh the other way... In terms of being able to run off grid totally, there is zero chance of that for me, I exported 11 MWh to the grid and pulled in 10.5 MWh, so almost 2/3 of my used power was when the solar was not producing energy.

I only use my 2 PWs for backup though, so I probably could get it down to 50% if I ran down the batteries every night. But with net metering here what would be the point? I'd be losing money on the inverting and storage losses.

As Tesla defines it in the app, "Energy Offset" includes solar energy sent to and from the grid. "Self-powered" includes only the amount of solar that was either directly used to power your home or sent to a powerwall and then used. So, as I understand it, your "Energy Offset" is slightly over 100% for the year while your "Self-powered" would be around 33%.

And I agree with you that with net metering (and no TOU rates), it does not make sense economically to chase a higher "Self-powered" score because of the energy losses, and it also likely will more quickly reduce the capacity of the powerwall. In the end, the goal would be to maximize "Energy Offset". But it may make sense for others with different rate structures. And, it can be an interesting experiment to see how close you can come to going off grid, including understanding what loads might need to be sacrificed or shifted in the event of an extended outage.

 

[Incredulocious]

I switched to self-powered as well once I saw that the balanced setting would immediately stop charging the Powerwalls when my time-of-use schedule switched mid-day. This would mean that I would end up needing grid power overnight since the batteries didn’t get fully charged.

After I switched to self-powered, I found that my two Powerwalls would get fully charged by mid-afternoon (9 kW solar system) and then spend the rest of the day exporting to the grid (and thus generating NEM credits) and I could then easily remain self-powered overnight. Thus I’ll get 100% self-powered (no grid usage) for most days from spring through most of autumn. The exceptions are days when one of our cars need a significant charge or if it’s cold and overcast enough to need to heat the house (heat pump).

My situation here (near the coast) is never really needing cooling in the summer, but lots of energy usage in the winter for the house heat pump. So my year long solar generation curve is opposite to my energy usage: heavy usage in winter, minimal the rest of the year – and that’s with everything electric: cars, house heat pump, water heater, electric clothes dryer, induction cooktop, electric oven, water well pump, pressure pump, water treatment system, septic system, etc. But I still get a net positive for the year with NEM credits and thanks to the Powerwalls allowing me to avoid needing grid power during evening peak usage times.

And yes, like the original poster, I am playing the 100% self-powered game. I often charge the car during the day when possible now just to use some of the excess solar and stay self-powered because it’s fun to be able to avoid using the grid at all for most of the time. And I’m still generating enough NEM credits to cover winter usage.

Here’s my month of May:

For more info, see my post on my Powerwall installation here:
Tesla Powerwalls Installed

And as for the non-backed up car charging circuit draining the Powerwalls, yes, I was initially surprised by this, but of course in hindsight it makes sense. There’s nothing stopping the flow of power to the “external” car charging circuit when the grid is live, else how could you export your excess solar to the grid? As for why the grid doesn’t drain the Powerwalls too, hmmm... I’m not clear on how that works.

 

[aesculus]

Thats not true. Non backed up circuts can be monitored by the placement of the CTs, and I believe that is how tesla normally sets it up unless you specifically say " I dont want the ability to power those loads with the powerwall, even if the grid is up.

Monitored I am OK with. Mine is monitored too. The OP said his PWs were discharged. I am still struggling with how a load on the other side of the backup would be discharged. That's the reason you put some loads in backup and other loads not backed up, to avoid this.

In fact, I would imagine, if you swap from the advanced setting that you are likely in, into self powered, you would see the same powerwall usage. What I see looking at your graph, is that when you charge your car, your system diverts any leftover solar to the powerwalls (why the big spike in powerwalls receiving power when you are charging your car?)

That's not my car, that's my AC, and they are backed up. The car is the spike on the far left of the graph.

 

[power.saver]

Monitored I am OK with. Mine is monitored too. The OP said his PWs were discharged. I am still struggling with how a load on the other side of the backup would be discharged. That's the reason you put some loads in backup and other loads not backed up, to avoid this.


That's not my car, that's my AC, and they are backed up. The car is the spike on the far left of the graph.

You were in StormWatch on June 27, right? Because after the peak period, you turned it on again, causing the PW to charge from the grid. That's why the PW shows a steady 6kW charge rate past sundown. That probably also explains why your car charging did not cause a discharge. The grid was up and you were essentially in backup only mode.

 

[jjrandorin]

Monitored I am OK with. Mine is monitored too. The OP said his PWs were discharged. I am still struggling with how a load on the other side of the backup would be discharged. That's the reason you put some loads in backup and other loads not backed up, to avoid this.


That's not my car, that's my AC, and they are backed up. The car is the spike on the far left of the graph.

Thats a choice. You put loads in or out of the backup loads so they dont run "during an outage". Running during an outage, or being able to be powered by powerwalls when the grid is up, are not the same thing. In fact, setup this way (so that non backed up loads can be powered by the powerwall when the grid is up) is VERY common, so its not like we have some "one off" setup or something.

In any case, as I mentioned, its not correct to say that non backed up loads are not powered by the powerwall when the grid is up. I am 100000% percent sure that statement is not correct. It all depends on where the CTs are located.

If you dont have the CTs in a place where the powerwall can monitor the non backed up loads, they are not seen by the system at all, thus the powerwall CANT power them. It appears that what you are showing is a screenshot of your car charging, but not showing in the app, which would make sense if your CTs are placed such that the powerwall has no idea of that load.

In many (not sure I would say "most" but definitely "many" non backed up loads are monitored by the powerwall, such that the powerwall can power them when the grid is up.

Here is a screenshot of My car charging. Note, my tesla wall connecter is NOT backed up, and in fact is the only thing in my home that is still in my main panel and not backed up. I have verified it is not backed up during my "simulated outage" tests, so I am 10000% sure this load is NOT backed up but still monitored so the powerwall can provide power:

That spike at noon (ish) is me charging my car. I was generating 6.2 ish of solar at that time, and with the car charging you can see the home load, and the fact that the powerwall is providing power.

Since you dont see your car charging in your app at all, it simply means the CTs are setup such that, that circuit is outside of the monitoring (so, your home usage numbers in the app will not include your car charging a all, and it is not monitored in the slightest in your case).

 

[aesculus]

While I was sort of in Stormwatch on the 27th I don't think that had anything to do with it. Since my car has not seen much serious driving for weeks I had to go way back to June 2nd to find anything more than an instantaneous spike at midnight to show the charging. Here is that one with NO stormwatch possible.

 

[jjrandorin]

While I was sort of in Stormwatch on the 27th I don't think that had anything to do with it. Since my car has not seen much serious driving for weeks I had to go way back to June 2nd to find anything more than an instantaneous spike at midnight to show the charging. Here is that one with NO stormwatch possible.

View attachment 561118

Ok now I am even more confused, because I was under the impression if the CTs were not placed so that you could use powerwall energy to power your backup loads, they wouldnt show in the app, but your charging shows in the app.

Shrug.. Im confused about that, but not confused about using powerwall energy to power non backed up loads, as I mentioned (yes, I am sure, like 10000%, that my HPWC is not on the backed up load side, I have tested it myself).

 

[aesculus]

If you dont have the CTs in a place where the powerwall can monitor the non backed up loads, they are not seen by the system at all, thus the powerwall CANT power them. It appears that what you are showing is a screenshot of your car charging, but not showing in the app, which would make sense if your CTs are placed such that the powerwall has no idea of that load.

I am totally confused on this. It sounds like our systems are the same but behave differently. Maybe it's the mode we are in?

My charger is also on my main panel. I checked the graph and yes, both the grid and home show the charger load, but no energy is coming from the powerwalls. But in your case they are.

I was in Cost Savings mode. What mode were you in when you charged and took the snapshot?

 

[BrettS]

While I was sort of in Stormwatch on the 27th I don't think that had anything to do with it. Since my car has not seen much serious driving for weeks I had to go way back to June 2nd to find anything more than an instantaneous spike at midnight to show the charging. Here is that one with NO stormwatch possible.

View attachment 561118

But in this case the powerwall isn’t powering anything in your house at that time. If you look after the car finishes charging you are still on 100% grid at that time, and the same thing in the following evening. After 8PM nothing in your house is being powered by the powerwall. So either the powerwall had no charge, was in backup only mode, or was below it’s backup threshold.

 

[BrettS]

I am totally confused on this. It sounds like our systems are the same but behave differently. Maybe it's the mode we are in?

My charger is also on my main panel. I checked the graph and yes, both the grid and home show the charger load, but no energy is coming from the powerwalls. But in your case they are.

I was in Cost Savings mode. What mode were you in when you charged and took the snapshot?

You need to do the test again at a time when the powerwall is powering your house.

 

[jjrandorin]

I am totally confused on this. It sounds like our systems are the same but behave differently. Maybe it's the mode we are in?

My charger is also on my main panel. I checked the graph and yes, both the grid and home show the charger load, but no energy is coming from the powerwalls. But in your case they are.

I was in Cost Savings mode. What mode were you in when you charged and took the snapshot?

Self Powered, same as OP.

My original guess was that your system is setup like mine, but since you are in cost saving mode it doesnt use powerwall energy because of the algorithms? I never use cost saving (or any of the advanced). i use either backup only, or self powered... mostly self powered.

 

[aesculus]

My original guess was that your system is setup like mine, but since you are in cost saving mode it doesnt use powerwall energy because of the algorithms? I never use cost saving (or any of the advanced). i use either backup only, or self powered... mostly self powered.

I think this must be it.

The powerwalls must be monitoring both the costs and the energy required and is making the best decision based on cost. Since my off peak charging is a fraction of my regular rate, it would probably never use powerwall power to charge the car.

As @BrettS stated if I did the same test during peak like you did, I would probably see the powerwalls contributing since they would be cheaper than the grid costs. I will try that later today for a few minutes to confirm.