Solar forecast and production graph is not correctly aligned in time axis

[javitonino]

Checklist

• [X] I have updated to the latest available Home Assistant version.
• [X] I have cleared the cache of my browser.
• [X] I have tried a different browser to see if it is related to my browser.

Describe the issue you are experiencing

The solar forecast production and forecast graph is not correctly aligned. The forecast line is 1 hour later than it should be. This is what it looks like in my installation.

Describe the behavior you expected

I expect the forecast to be closer to the actual production values. This is what it looks like if I shift the solar forecast by one hour (by doing time -= 3600000 in the javascript console while rendering the graph):

I think the problems comes from how the timestamp is picked for each data source:

• For solar production, the data comes from statistics. The time shown in the graph is the start of the measurement period, e.g: the energy produced between 10:00 and 11:00 will be shown at 10:00
• For solar forecast, the data comes from forecast.solar API. In this case, only a timestamp is returned per period, and it's the end of the period, i.e: it works as a meter, the timestamp reflects the measurement time and the value is the power estimated to be produced up to that date.

Steps to reproduce the issue

1. Configure the energy component with a source of data for photovoltaic production and forecast
2. Wait to gather some data
3. Observe that the forecast always seems to be shifted by one hour in time

What version of Home Assistant Core has the issue?

2021.10.6

What was the last working version of Home Assistant Core?

No response

In which browser are you experiencing the issue with?

Firefox 93.0

Which operating system are you using to run this browser?

Arch Linux

State of relevant entities

No response

Problem-relevant frontend configuration

Using the energy component to display solar production and forecast.

Solar production comes from a photovoltaic power sensor in Fronius integration. Since this reports power, I use a integration platform to sum the data into energy values per hour.
Solar forecast uses the default forecast.solar integration.

Javascript errors shown in your browser console/inspector

No response

Additional information

I think there are two possible solutions:

• Use the end date of each statistics period as the timestamp for the X axis. This probably means adjusting it in other energy-component graphs for consistency.
• Shifting the forecast data by one hour in the graph.

The changes should be easy enough. I'll try to set up the development environment and test both approaches in order to submit a PR later this week if I get some time 🤞.

[bramkragten]

Solar production comes from a photovoltaic power sensor in Fronius integration. Since this reports power, I use a integration platform to sum the data into energy values per hour.

Wait, you update the energy sensor value ones an hour? When do you do that?

[bramkragten]

For me personally, the forecast and production do line up correctly, so I'm not sure if your analysis is correct, I'll do some research.

[bramkragten]

(btw, maybe stupid question, are your browser and home assistant in the timezone of your solar panels location?)

[javitonino]

Wait, you update the energy sensor value ones an hour? When do you do that?

It's done continuously, by adding up the power values. It's achieved with the integration sensor: https://www.home-assistant.io/integrations/integration/. My PV system does not report the energy values (only power), so this basically calculates an integral of the power over time to get the energy.

(btw, maybe stupid question, are your browser and home assistant in the timezone of your solar panels location?)

There are no stupid questions :). Yes, everything is in the same timezone.

For me personally, the forecast and production do line up correctly, so I'm not sure if your analysis is correct, I'll do some research.

Hmmm, it's possible that this is caused by some weirdness with the sensors, but it really seems like a graphing issue. Maybe the graph makes some assumptions that do not hold in my configuration.

I have verified the following data manually:

• My PV system produced 1.73kWh of electricity between 9:00 and 10:00 local time.

  • This is shown in the graph as a bar at 9:00 in the X axis.
  • The legend (on hover) for that bar correctly displays that this value is for 9:00-10:00

• The solar forecast API returns 1.78kWh for the timestamp at 10:00. The result also identifies the correct timezone.

  • This is displayed in the graph as a point of the line at 10:00
  • The legend (on hover) incorrectly displays that this value is for 10:00-11:00

I am assuming that the PV production data is correct and that the solar forecast one is shifted based on the legend that appears on hover. Can you check if you get reasonable start/end times in that tooltip? Are your bars also centered around the start time of the measured period?

Otherwise, in my configuration, it would make sense that the incorrect data is from the production sensors because it's using the integration platform which is probably less used. The solar forecast integration should be pretty much the same in all configurations, so it should be less problematic.

Maybe there is a bug with the legend here? I may have a misconfiguration regarding the production values and the solar forecast may be alright. I'm only assumming the problem is in the forecast because of that tooltip.

[KNXBroker]

I have recognized the same.

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