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Cooling Strategies with PV + ESS

airboyd

Member
Sep 10, 2020
28
8
Southern California
I'm having a similar problem. 37 panels 11.84Kw system 2 Powerwalls.
SDGE On Peak 4-9 running TOU EV 5 running advanced balanced for TOU.

Both PW are full well before 4PM. At 4PM the software send excess to the grid and starts discharging the PW.

Sunset is about 7:30 right now and I'm making power until right up to sunset. I'm still generating enough solar at 5PM to run an AC.

AC set to 78 and it clicks on about 4:30. Cool enough to use Whole House Fan at about 6:30PM.

Balanced seems to do what it's supposed to using only PW 4-9. However, I could run an AC for about 2 hours of solar at that time instead of using battery.

MY charges midnight to 6:00, super off peak. It looks like the only way for the app to maintain the super off peak being grid only, is to use the advanced settings, so I'm stuck with balanced. I tried cost savings and it doesn't seem to change.

Is there any other way to force it to use the solar instead of the PW at 4PM until the solar can't support the AC so that I can run the AC right at the beginning of On Peak?

It seems like Tesla REALLY wants me to send excess to the grid on peak, but I'd rather it powered the house. Starting using the Powerwalls at 4 instead of 6/7 means they get really low overnight while using whole house fan when they'd be better off starting later. I'm afraid to move on peak later to trick it because that doesn't account for cloudy days etc...

I need a self powered, except for 4-6 if the PW are charged and MY always charges super off peak midnight-6 not touching the battery setting...

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MorrisonHiker

S 100D 2021.4.18.2
Mar 8, 2015
9,833
9,203
Colorado
I need a self powered, except for 4-6 if the PW are charged and MY always charges super off peak midnight-6 not touching the battery setting...
To accomplish that, try using one of the Time Based Control options. We use TBC-Balanced but extend the part-peak hours so that our household is self-powered for 20+ hours a day. Our peak period is always covered by our solar and Powerwalls. One of our cars charges from the grid during off-peak, right when the Powerwalls stop powering things. Another car later charges with grid power, solar and whatever surplus is leftover in the Powerwalls. A third car is always charged via solar.
 

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airboyd

Member
Sep 10, 2020
28
8
Southern California
To accomplish that, try using one of the Time Based Control options. We use TBC-Balanced but extend the part-peak hours so that our household is self-powered for 20+ hours a day. Our peak period is always covered by our solar and Powerwalls. One of our cars charges from the grid during off-peak, right when the Powerwalls stop powering things. Another car later charges with grid power, solar and whatever surplus is leftover in the Powerwalls. A third car is always charged via solar.
I'm on balanced now, but my system keeps sending useable solar to the grid the first few hours of peak instead of running my house and discharging the batteries because it's on peak.

That's the issue I'm trying to figure out here. I can use the AC in the early evening (4-6) but it always discharges battery on Balanced. I've got solar production down to almost sunset at 7:20 right now login from high 5Kw at 4 down to 600 at the end.

It's sending solar to the grid, enough solar to run an AC unit. You can see the flip flop in my graph above where I changed to self powered to see if it would take the AC unit. It was enough to run the AC and the house of pure solar at 5:30.

I'd rather it ran the A/C for an hour or so instead of fed the grid and, especially - not take 2 hours of high Kw use out of the Powerwalls while I'm making solar.
 

MorrisonHiker

S 100D 2021.4.18.2
Mar 8, 2015
9,833
9,203
Colorado
I'm on balanced now, but my system keeps sending useable solar to the grid the first few hours of peak instead of running my house and discharging the batteries because it's on peak.

That's the issue I'm trying to figure out here. I can use the AC in the early evening (4-6) but it always discharges battery on Balanced. I've got solar production down to almost sunset at 7:20 right now login from high 5Kw at 4 down to 600 at the end.

It's sending solar to the grid, enough solar to run an AC unit. You can see the flip flop in my graph above where I changed to self powered to see if it would take the AC unit. It was enough to run the AC and the house of pure solar at 5:30.

I'd rather it ran the A/C for an hour or so instead of fed the grid and, especially - not take 2 hours of high Kw use out of the Powerwalls while I'm making solar.
We always used Balanced for our needs as we want to export all solar during peak since we earn peak credits on all power exported. Have you tried the Cost Saving mode to see if it would work better for you?
 
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MJ_CA_2019

Member
Aug 19, 2020
149
37
Central CA
We always used Balanced for our needs as we want to export all solar during peak since we earn peak credits on all power exported. Have you tried the Cost Saving mode to see if it would work better for you?
@airboyd Are you saying you don't want credits at peak rates? You are in SoCal so assuming you are on Net Metering; are you on a TOU plan?

The Advanced modes (balanced / cost savings) appear to be built specifically for TOU users. Even with the 90% round trip efficiency it should be worth it to store at off peak rates and run your house off the PW while exporting at peak rates.
 

airboyd

Member
Sep 10, 2020
28
8
Southern California
@airboyd Are you saying you don't want credits at peak rates? You are in SoCal so assuming you are on Net Metering; are you on a TOU plan?

The Advanced modes (balanced / cost savings) appear to be built specifically for TOU users. Even with the 90% round trip efficiency it should be worth it to store at off peak rates and run your house off the PW while exporting at peak rates.

SDGE EV TOU 5

I'm fine with it trying to maximize credits, but in this case I disagree with it's logic using storage, but it might just be me...

On a non-foggy/marine layer morning, my PWs are usually full by noon. I'm shoving ~30Kwh back into the grid in the next 4 hours.

AC is using approx 3500Kwh at 4PM while my PWs are full and solar is still generating in excess of that and returning to the grid.

Using 3500Kwh for 2 hours out of the batteries vs using the sun for 2 hours sees like a waste to me. It's taking the PWs down below 68% before dark and while I'm producing sun. It just feels like I'm using a lot of PW energy that could be better allocated. I could be wrong and, as it's a new system, I've got a few more weeks to find out where my TOU NEM is sorting itself out.

It's just the bridge of the AC from hot afternoon until we can switch to the whole house fan. It's a 2-3 hour window.

Like I said, it might just be me, but I I'd rather have those 2 hours of high draw AC powered by the sun. IF NOT for running the AC, I wouldn't care. I jumped in here on this thread because it's a cooling vs efficient discussion and it's had me thinking for a while.
 
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h2ofun

Active Member
Aug 11, 2020
2,658
490
auburn, ca
SDGE EV TOU 5

I'm fine with it trying to maximize credits, but in this case I disagree with it's logic using storage, but it might just be me...

On a non-foggy/marine layer morning, my PWs are usually full by noon. I'm shoving ~30Kwh back into the grid in the next 4 hours.

AC is using approx 3500Kwh at 4PM while my PWs are full and solar is still generating in excess of that and returning to the grid.

Using 3500Kwh for 2 hours out of the batteries vs using the sun for 2 hours sees like a waste to me. It's taking the PWs down below 68% before dark and while I'm producing sun. It just feels like I'm using a lot of PW energy that could be better allocated. I could be wrong and, as it's a new system, I've got a few more weeks to find out where my TOU NEM is sorting itself out.

It's just the bridge of the AC from hot afternoon until we can switch to the whole house fan. It's a 2-3 hour window.

Like I said, it might just be me, but I I'd rather have those 2 hours of high draw AC powered by the sun. IF NOT for running the AC, I wouldn't care. I jumped in here on this thread because it's a college vs efficient discussion and it's had me thinking for a while.
Can you not change your peak to 6pm then?
 

airboyd

Member
Sep 10, 2020
28
8
Southern California
We always used Balanced for our needs as we want to export all solar during peak since we earn peak credits on all power exported. Have you tried the Cost Saving mode to see if it would work better for you?

It didn't seem to make much difference in playing around this week, but I might have to let it sit longer on a few more days and see if it sorts itself out.
 

airboyd

Member
Sep 10, 2020
28
8
Southern California
Can you not change your peak to 6pm then?

I guess that hack is the only real choice for summer and then put it back to 4PM for winter. I wanted to try and leave it at 4PM since that's a constant year round, but it might not be possible. I'll have to look into the SmartThings App and see if I can just automate that function.
 

h2ofun

Active Member
Aug 11, 2020
2,658
490
auburn, ca
I guess that hack is the only real choice for summer and then put it back to 4PM for winter. I wanted to try and leave it at 4PM since that's a constant year round, but it might not be possible. I'll have to look into the SmartThings App and see if I can just automate that function.
only takes seconds to change
 

MJ_CA_2019

Member
Aug 19, 2020
149
37
Central CA
Like I said, it might just be me, but I I'd rather have those 2 hours of high draw AC powered by the sun. IF NOT for running the AC, I wouldn't care. I jumped in here on this thread because it's a cooling vs efficient discussion and it's had me thinking for a while.
Ideally the battery would make it through all the way until the sun comes back up.
If not, then the next best thing is making sure that zero draw from the grid happens during peak rates.
Exporting during peak rates > storing energy off peak and using battery during peak.

I'm fairly convinced not that it's not worth trying to pre-cool. That's a slightly different question than you are asking, because I was wanting to do it BEFORE peak rates start at 4:00 pm. I'm happy with the Balanced behavior and how it exports.
 
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ccrowder

Member
Mar 25, 2021
12
24
San Diego
It basically is trying to maximize your cost savings. By using the PW after 4p to run the AC while dumping the PV to the grid you are getting more bang for your buck. You are using energy in the PW that would have exported to grid at ~0.30/kW instead of using PV energy at that time which is now being exported to grid at 0.60/kW. And since with the EV5 TOU of 0.09/kW for midnight to 6am it does not matter if you deplete your PW (up to your minimum for backup) and pull from the grid over night since it is so cheap.

It basically boils down to money. If you use your PV 'excess' to power the AC after 4pm just to save more PW for use late evening/early morning you are using energy that has a "higher" value more to have more battery power later when it has 'less' value. (if that makes sense)
 

airboyd

Member
Sep 10, 2020
28
8
Southern California
It basically is trying to maximize your cost savings. By using the PW after 4p to run the AC while dumping the PV to the grid you are getting more bang for your buck. You are using energy in the PW that would have exported to grid at ~0.30/kW instead of using PV energy at that time which is now being exported to grid at 0.60/kW. And since with the EV5 TOU of 0.09/kW for midnight to 6am it does not matter if you deplete your PW (up to your minimum for backup) and pull from the grid over night since it is so cheap.

It basically boils down to money. If you use your PV 'excess' to power the AC after 4pm just to save more PW for use late evening/early morning you are using energy that has a "higher" value more to have more battery power later when it has 'less' value. (if that makes sense)
It’s just the change in adding the PWs for me. My house is now charging/powering a large device and that’s new to me.

We exported more than we produced before the PW. Even on rate DR.

My pool equipment and AC run off solar until the sun went down with all excess going to the grid.

A lot of excess charges the battery first then the grid and it’s just a new concept seeing it.

If not for AC and MY charging, we could stay on self powered.

I’ve had 3 years of running the pool equipment off the sun and now it’s sharing with the grid. It’s just new and I’ll adjust the time later in the day to make up for it.

It clearly says that it will use the battery in all periods. It’s just not how I was using pure solar alone….

Will see how it tracks over the summer.

A9FFCFF7-B049-440C-AA24-F87DCA348E23.jpg
 
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