Help with understanding PowerWall 2 available energy hours ?

[P@dge]

As an experiment set your Powerwalls to 100% backup. Then let your house only consume grid energy overnight. Post the graph the next day so we can see what your Home load was overnight. It should overlay the grid graph. The PW graph should obviously be flat.

Thanks Aesculus, I'm currently scheduled to turn ALL OFF except for my Water Pump and Water Filter system tonight.
I will capture that Grid usage since Solar and Battery are already dark and I will set up for Backup only.
I am trying to see how each device shows kW's used / added to the total over the next few days... Will keep everyone updated.

 

[getakey]

get one of these
Sense: Track energy use in real time to make your home more energy efficient.

 

[dareed1]

I'm using Emporia Vue Gen 2. $110 for 8 50A CTs plus 2 200A CTs, so close to one third the cost of Sense.
Emporia Vue is an Interesting Companion to Solar and Powerwalls
Some people get the $170 set with 16 50A CTs; my panel would be getting a little cluttered if I mounted 16.

Anyway I have a Mitsubishi 2.5 ton heat pump with a single ducted air handler. I went with Mitsubishi partly for efficiency and partly for low noise from the outdoor unit. The outside air "never" goes below freezing here so I don't have a Hyper Heat version. The Hyper Heat versions take about 25% more power for a given heating output, but of course are able to run lower than 15F.

You probably can see how much power your heat pumps are supposed to use by navigating around at MyLinkDrive. For example the 900 page M-series Technical Data Book 01_2021 contains a wealth of information including heating output versus power draw at 5 degree intervals.

 

[P@dge]

You guys and gals are AWESOME !! Thanks so much... I'll respond here to everyone's analysis
NOTE: I misquoted in the original post... I didn't turn off ALL energy consuming devices !!
I turned of ALL lights, oven, washer, dryer, pc's, clocks, with exception to the devices found
below in item #2 .
RESPONSES:
1. YES, I need to get a better grip on what's actually consuming my energy if I'm using above 3kW overnight.
2. My energy uses overnight for my 1,100 sq.ft. , OPEN SECOND FLOOR LOFT (20' ceiling) are as follows:
a. (4) Mitsubishi Mini Splits running 24 hours with single compressor and distribution box in crawl space.
Set to 68deg.
b. (1) Whirpool Energy Efficient 25cu.ft. fridge.
c. (1) ancient RCA 20.6cu.ft. fridge in garage(attached, unheated).
d. (1) Rheem Energy Efficient 45gal. elec. water heater (no additional insulation wraps) in garage.
e. (1) Fridgidaire Energy Efficient 12.8cu.ft. chest freezer in garage (apocalypse ready)
f. (1) Standard, deep well, water pump (usually doesn't run during overnight) in garage.
g. (1) Rainsoft water filter (2 tanks), with Ultra-violet light attachment in garage.
3. We had just been in our new home for 5 months when the third party installer did the sizing based
on the Grid usage they reviewed from our provider... we added (2) Energy consuming devices
that we turn OFF during our testing now that would really skew any numbers for our consumption via
normal home device consumption. i.e. Greenhouse Heater this Winter (turn off for overnight testing),
and an Airstream Heat Pump on 19ft.er that would be turned OFF also , but run other times during
Solar hours, so we can't give true consumption rates with past data, only our "controlled" test data.

I think all of you have hit the nail on the head for us to find out each consumption rates, over and above,
staying warm, including turning off all of a. thru g. above for the overnight, turning on individual things
1 at a time over a period of 7 nights I guess... this actually sounds kinda cool.... getting controlled usage
by device, then devices and reviewing the Tesla Mobile App data for the given hours .
I certainly will be writing back with our plans for device usage and report back on consumption

OK.. here we go after last night's first test...
Start Time = 10:30pm Eastern, 46deg.
End Time = 6:30am Eastern, 48deg.
Devices Running = Water Pump
Water Filter with UV Light
Inside House Fridge
Supporting Graph(s) and Mobile App Data below :

 

[aesculus]

So from 10PM to 6Am your energy use is trivial. So your Powerwalls should not be draining during that period.

Did you check the SoC of the Powerwalls between 10PM and 6AM? You might loose a few percent which is normal.

 

[h2ofun]

OK.. here we go after last night's first test...
Start Time = 10:30pm Eastern, 46deg.
End Time = 6:30am Eastern, 48deg.
Devices Running = Water Pump
Water Filter with UV Light
Inside House Fridge
Supporting Graph(s) and Mobile App Data below :
View attachment 640677 View attachment 640676

what are those spikes? Do you turn your mini splits on then?

 

[jhn_]

Looks like the high energy offenders are in the group of things you turned off in this test.

 

[jjrandorin]

So from 10PM to 6Am your energy use is trivial. So your Powerwalls should not be draining during that period.

Did you check the SoC of the Powerwalls between 10PM and 6AM? You might loose a few percent which is normal.

I took those graphs to be "we turned off everything we could" not " this is my homes normal overnight energy usage". I am not 100% sure of that though, and am also not sure what OP is now attempting to figure out.

I am not sure if they are trying to figure out how long they "could" go if they turn everything off in a power outage, or how long they "should" be able to go if their home uses its normal amount of electricity overnight.

 

[P@dge]

So from 10PM to 6Am your energy use is trivial. So your Powerwalls should not be draining during that period.

Did you check the SoC of the Powerwalls between 10PM and 6AM? You might loose a few percent which is normal.

I'm learning What is SoC ? I was not awake, so if it takes monitoring then I did not. Oh.. and do the Powerwalls
use energy just sitting there ?

 

[Vines]

I'm learning What is SoC ? I was not awake, so if it takes monitoring then I did not. Oh.. and do the Powerwalls
use energy just sitting there ?

Powerwalls consume energy just keeping themselves awake and healthy. They monitor temperature and circulate coolant as needed. If very cold they will use power to keep warm.

I understand this to be something as small as 300wH per day per Powerwall in ideal conditions.

 

[P@dge]

I took those graphs to be "we turned off everything we could" not " this is my homes normal overnight energy usage". I am not 100% sure of that though, and am also not sure what OP is now attempting to figure out.

I am not sure if they are trying to figure out how long they "could" go if they turn everything off in a power outage, or how long they "should" be able to go if their home uses its normal amount of electricity overnight.

Hey JJ... I'm just trying to see which devices are the "drivers" of our overnight usage by turning on for that test period of time overnight.
Like, tonight , I'm planning on adding my Water Heater to the mix and see total usage when that's on for the time, then Freezer Chest next night, Garage Fridge next, and finally the Mitsubishi units , which will be ALL of the units for the test... I think h2o has it right that it is probably going to be the (4) Split units driving my overnight use.... that will be a bummer for me :-( Made assumptions the design was created to cover ALL YEAR USE, not just Spring thru early Fall right ?

 

[Electrph]

not sure if mentioned in thread already but u can purchase something like this monitor 110v non hard wired loads
seems less of a chore

 

[jjrandorin]

Hey JJ... I'm just trying to see which devices are the "drivers" of our overnight usage by turning on for that test period of time overnight.
Like, tonight , I'm planning on adding my Water Heater to the mix and see total usage when that's on for the time, then Freezer Chest next night, Garage Fridge next, and finally the Mitsubishi units , which will be ALL of the units for the test... I think h2o has it right that it is probably going to be the (4) Split units driving my overnight use.... that will be a bummer for me :-( Made assumptions the design was created to cover ALL YEAR USE, not just Spring thru early Fall right ?

You can probably skip the rest of the testing except for the mini splits. If someone told you that 2 powerwalls would be enough, given your 70kWh a day of home usage, and the desire for "days" of backup, they told you incorrectly.

 

[charlesj]

I see you mentioned "water pump" as on. What is the purpose for that as my imagination is running rampant what it could be.
Perhaps that is the spike when it came on for a bit? Is it a well pump? Or recirculating hot water pump? Or any other I could imagine?
Water filter with UV light operates when water is being drawn or used and off when not?

 

[Electrph]

I see you mentioned "water pump" as on. What is the purpose for that as my imagination is running rampant what it could be.
Perhaps that is the spike when it came on for a bit? Is it a well pump? Or recirculating hot water pump? Or any other I could imagine?
Water filter with UV light operates when water is being drawn or used and off when not?

OP mentioned "standard deep well water pump" believed did not run at night .. also has some other interesting electrical devices ..whole house water filter w/ UV ?
but i too would like to hear more details on these pump(s) / filters etc

 

[P@dge]

what are those spikes? Do you turn your mini splits on then?

No... actually turned off the Branch Box and the main Mitsubishi breaker at 10:00pm ...
The short spike at Midnight for 15min. (per graph data), were basically still below 1kW .
I just don't know what that would have been unless the Fridge turned on for that 15min maybe ?
It would not have been the water pump cause I tested that prior and the pump used 2kW for 1 minute.
i.e. I had everything shut down and then ran the cold water until the pump turned on... where I noted
the Mobile App usage as 2kW and the pump turned of in 60seconds, returning the App usage to .3kW

 

[P@dge]

I see you mentioned "water pump" as on. What is the purpose for that as my imagination is running rampant what it could be.
Perhaps that is the spike when it came on for a bit? Is it a well pump? Or recirculating hot water pump? Or any other I could imagine?
Water filter with UV light operates when water is being drawn or used and off when not?

Hey Charlesj, The water pump is from Deep Well (country boy here) and I never turn that off. I just posted that usage below
which is nothing for the 1 minute period it would run... There should all but NEVER be a need for that to turn on thru the
night unless I had some sort of water leak .

 

[aesculus]

You can probably skip the rest of the testing except for the mini splits. If someone told you that 2 powerwalls would be enough, given your 70kWh a day of home usage, and the desire for "days" of backup, they told you incorrectly.

I am totally with you on this one. And if these devices are not defective (seriously doubt they are) then this exercise is significant for me to never consider mini-splits, not that I was thinking about it.

My decades old, super inefficient, standard forced air heat pumps use less energy than this during colder outside air in a 4k sq foot house with tons of windows. And I thought the whole value of mini splits was that you could have different temps per system so you were not heating spaces you were not occupying.

OP says they have them set to 68F in a 1100 sq foot loft but did not note the main living space setting.

 

[P@dge]

OP mentioned "standard deep well water pump" believed did not run at night .. also has some other interesting electrical devices ..whole house water filter w/ UV ?
but i too would like to hear more details on these pump(s) / filters etc

Hey Electrph,... the filters are inline between the pump/well and the standard expansion tank.
There are 2 tanks, RainSoft EC4 Technology which feed the water thru the RainSoft UV device (S8Q-PA-R).
There is a scheduled "backflush" process the filter beds go thru every Wednesday which takes about an hour.
This happens at 1:00am .... so that would not have showed up last night .

 

[n.one.one]

You can probably skip the rest of the testing except for the mini splits. If someone told you that 2 powerwalls would be enough, given your 70kWh a day of home usage, and the desire for "days" of backup, they told you incorrectly.

For someone planning a system would 3 Powerwalls be enough for 70kWh a day? Should 4 PW be given any consideration.

Let me add that obviously there are other important factors like system size in kW, geographic location (solar production), roof direction/angle, utility rates and rules (is system kW size limited to qualify for net metering as it is in Georgia), budget, etc.