Apps shows kWh while download has kW

[GoingSolar]

I am really having a hard time understanding how they come up with large kW. When you multiply with total time (h), it is hugely large kWh value. Let alone the total kW to begin with is larger than kWh reported by the app.

I need to understand their logic so I can pull and process it for further analysis.

Example:
Home (kW) = 317.90 in 24 hours. So to get you would do 317.90 x 24 yields 7,639.6 kWh. Whereas Tesla app says 26.0 kWh

From Powerwall (kW) = 161.4 app says 13.1 kWh

Solar (kW) = 446.6, app says 37.4 kWh

Of course for Solar and PW, I found exact hours based on each line item 5 min apart.

math just doesn’t work?
Am I doing something wrong?

 

[gpez]

I am really having a hard time understanding how they come up with large kW. When you multiply with total time (h), it is hugely large kWh value. Let alone the total kW to begin with is larger than kWh reported by the app.

I need to understand their logic so I can pull and process it for further analysis.

Example:
Home (kW) = 317.90 in 24 hours. So to get you would do 317.90 x 24 yields 7,639.6 kWh. Whereas Tesla app says 26.0 kWh

From Powerwall (kW) = 161.4 app says 13.1 kWh

Solar (kW) = 446.6, app says 37.4 kWh

Of course for Solar and PW, I found exact hours based on each line item 5 min apart.

math just doesn’t work?
Am I doing something wrong?

A screenshot would be super helpful

 

[Hebert]

Let's see if this helps... Kw is an measurement without time. It could have been measured at any instant during the day. A home consumes a variable amount of watts as time goes on.

Kwh for the day would be a series summation of many Kw and time duration measurements.

 

[charlesj]

Someone may explain this better but here is what is happen ing>
That 317.7 is Watts, instantaneously at the time of display, that is power. I you'd watch it constantly all day, it would read different at each change of consumption and time as the readout may not be constantly instantaneous. At end of day or when you tap the home in the power flow window, you will have all sorts of spikes all day and the app automatically integrates very small time periods of Watt power and you will see the Watt hour total from midnight to the time of day when you look.

Same applies to the other buttons, solar, PW and Grid. Over time it becomes Wh; a snippet a small slice in time is just Watts.

I am watching my app this instant and home power fluctuates from 0.6kW to 0.7kW as that is what the house happens to need at that time;

Hope this helps.

 

[tkizzy]

I’m not sure exactly what you’re asking, but...
kW is a measure of instantaneous power, kWh is a measure of stored/used energy content.

if you charge at power level 7 kW, 1 hour of charging will give you 7 kWh capacity.

I doubt you have a 317 kW solar array unless you have a palace.... that’s like a Tesla hard accelerating to use that much instantaneous power.
Maybe it’s 0.317 kW (317 Watts) average power level ....> .317 W *24h = 7.6 kWh ... which also doesn’t match 26 kWh....

 

[GoingSolar]

Let's see if this helps... Kw is an measurement without time. It could have been measured at any instant during the day. A home consumes a variable amount of watts as time goes on.

Kwh for the day would be a series summation of many Kw and time duration measurements.

Correct. So in the download it has entries every 5 minutes. The sum of all these entries is 317.90 kW, and the total time span is 24 hours. The header row says kW.

 

[GoingSolar]

Someone may explain this better but here is what is happen ing>
That 317.7 is Watts, instantaneously at the time of display, that is power. I you'd watch it constantly all day, it would read different at each change of consumption and time as the readout may not be constantly instantaneous. At end of day or when you tap the home in the power flow window, you will have all sorts of spikes all day and the app automatically integrates very small time periods of Watt power and you will see the Watt hour total from midnight to the time of day when you look.

Same applies to the other buttons, solar, PW and Grid. Over time it becomes Wh; a snippet a small slice in time is just Watts.

I am watching my app this instant and home power fluctuates from 0.6kW to 0.7kW as that is what the house happens to need at that time;

Hope this helps.

I agree, in THE App it has kW spikes of power, and above the graphs it tallies that into one single data kWh. So in essence, it has taken into sum of these kW of power drawn in a time duration and multiplied against the time yielding kWh. I want to compare previous days final app data against the one I download as a .cvs

 

[tkizzy]

Correct. So in the download it has entries every 5 minutes. The sum of all these entries is 317.90 kW, and the total time span is 24 hours. The header row says kW.

Again, kW is a measure of instantaneous power - you need time for any given kW value to know how much absolute energy was used. So if the list has entries every 5 minutes (assuming these aren’t arbitrary samples and are in fact zero-sum), you need to calculate how much absolute energy was used for each 5 minute period (5/60 hour period) and then add THOSE up together. so if list is (2 kW, 1.5 kW, 3 kW), do:

(5/60)*2+(5/60)*1.5+(5/60)*3 = 0.54kWh... would give you the energy used inside of 15 minutes (3x5min, again assuming that’s what this data is)

 

[GoingSolar]

I’m not sure exactly what you’re asking, but...
kW is a measure of instantaneous power, kWh is a measure of stored/used energy content.

if you charge at power level 7 kW, 1 hour of charging will give you 7 kWh capacity.

I doubt you have a 317 kW solar array unless you have a palace.... that’s like a Tesla hard accelerating to use that much instantaneous power.
Maybe it’s 0.317 kW (317 Watts) average power level ....> .317 W *24h = 7.6 kWh ... which also doesn’t match 26 kWh....

Do this, from your app (see attached screenshot), do a download, I generally use Excel to open it as csv file. You will get header showing (kW) with some like 285 rows. Total the column will give you a sum of data points. Each data point increments in 5 min time.

 

[power.saver]

317/12=26

317kWh (your total) divided by 12 (the number of periods in an hour) = 26kWh

 

[GoingSolar]

Again, kW is a measure of instantaneous power - you need time for any given kW value to know how much absolute energy was used. So if the list has entries every 5 minutes (assuming these aren’t arbitrary samples and are in fact zero-sum), you need to calculate how much absolute energy was used for each 5 minute period (5/60 hour period) and then add THOSE up together. so if list is (2 kW, 1.5 kW, 3 kW), do:

(5/60)*2+(5/60)*1.5+(5/60)*3 = 0.54kWh... would give you the energy used inside of 15 minutes (3x5min, again assuming that’s what this data is)

I did a exactly that for each 5 min data point and multiplied with 5/60 yields. I did that for smaller data point like from PW.

i am now going to do what you are referring to, i.e. in excel create extra column and apply the math and then sum it. What I did was write up the formula to do match do the count and come up with single kWh value. Now I am going to break it step by step by adding columns and then doing match.

I suspect same results, but I won’t know till I try it

 

[GoingSolar]

317/12=26

317kWh (your total) divided by 12 (the number of periods in an hour) = 26kWh

I will go back and try that. Funny you mentioned periods in an hour. So I remember taking the sum and dividing with what solar would give and the values were always around 12, like 12.2, 12.3, 12.1, 11.9 and I wondered the whole number factor was around 12, but couldn’t explain why?
It makes sense the reason of +/- .3 is probably due to rounding on the app or at my end. I think you are on the track. Let me plug this and see what I come up with.

 

[gpez]

I will go back and try that. Funny you mentioned periods in an hour. So I remember taking the sum and dividing with what solar would give and the values were always around 12, like 12.2, 12.3, 12.1, 11.9 and I wondered the whole number factor was around 12, but couldn’t explain why?
It makes sense the reason of +/- .3 is probably due to rounding on the app or at my end. I think you are on the track. Let me plug this and see what I come up with.

This is the answer.

The column you're seeing as "kW" is probably better described as "average kW over the period" where the period is 5 minutes. To convert that value to kWh you would multiply the average kW over that time period by the time period. If you add up all of those calculated kWh values you should get very close to the total the app is reporting for the day.

For example if your average kW for a 5 minute period was 2kW then your produced 2 * 5 / 60 = 0.166kWh during that time.

EDIT:
Maybe this will help

 

[wjgjr]

The column you're seeing as "kW" is probably better described as "average kW over the period" where the period is 5 minutes.

While I agree that for most purposes, including the one under discussion, this is a very good approximation, I would note for anybody needing more precise data that I believe Tesla is correct in labeling the data as "kW" as it seems to be instantaneous power readings. Having looked at the app output, I found that on sunny days, there is very good alignment between the data logged from the API and the app. However, on cloudy days, there is much more variability, though in the end it typically mostly balances out.

As a note, it also appears to be the case that the daily totals reported by the app are based on the "meter" data that can be pulled from the API, so they are not directly tied to the instantaneous data. That is why they may not match, and, where there is a discrepancy, it is likely the daily totals are more accurate, with a couple of caveats. First, because of the way Tesla rounds its meter data, you can have a day where you produce 10.01 kWh of solar, and Tesla might report it as 10.1 kWh, or a day with 9.99 kWh that Tesla might report as 9.9 kWh. Second, as I mention elsewhere, there is a bug I was reminded of again that (at least for a few of us) causes the data from 3 days ago to be reported low.

 

[GoingSolar]

Thank you. All great answers. Both "gpez" and "power.saver" gave yields same answer. As "wjgjr" indicated, these are good approximations as they are close, so don't know which is really accurate, but since Tesla is recording every 5 minutes in the downloaded data, I would assume it is more accurate than the App, more so as it is unknown how they compute to what decimal places, etc. etc.

So it worked for - Home & Solar, but not so for the Powerwall and the Grid.

I wanted to know how much power is coming from & going to Powerwall, and same for Grid, from Grid and into Grid.

So I broke down each into 2 buckets. If +ve, then From PW, and -ve To PW. Same for Grid.
Using either gepz's or power.saver, I got good results for Powerwalls & Grid for the "From's". Could not validate the "To's", but assuming it should be good if same method is applied for the From.

Thanks everyone for replying, like I said, all great answers with good explanations.

 

[GoingSolar]

I realized that if you scroll down a bit it will provide you To PW and under Grid, To Grid as well. So I should be able to validate those numbers also.

Question: if you push more than you draw, does SCE or PG&E complain to you for the month end total? I have SCE. Currently I am at 100% self sufficient for this week, and have been pushing back to SCE.

Since I don’t have PTO as yet still waiting on City inspection, anything that I push probably will not show on the Tiered plan bill.

 

[jrweiss98020]

You may find out that you will be charged for the electricity you push to the grid...

Some non-net-metering meters have 'tamper detection' that detects reverse flow of electricity, and will record it as electricity being drawn from the grid. If you do not have PTO, you should disconnect from the grid when you power on the solar panels.

 

[Ampster]

New You may find out that you will be charged for the electricity you push to the grid...

I have never seen that happen with SCE or PG&E on the few instances where a circuit was turned on before PTO. However there are many other situations where that is true. In all cases it is not recomended.
A good friend, on PG&E, had a 14 month delay on a PTO with one of the above companies and to this day he still does not know how his breaker was turned on but he did charge his cars from the power generated so as not to send too much to the grid. He remarked that it was the least he could do to help PG&E through the bankruptcy.

 

[gcsutton]

He remarked that it was the least he could do to help PG&E through the bankruptcy.

Funny