Make energy-date-selection dates usable for front-end templating

[danir-de]

Currently we have a pretty awesome date-time range selector in form of the energy-date-selection card.
The values of this card (start date, end date,...) can currently be used by three types of cards using the "energy_date_selection" variable:

• Statistic card
• Statistics graph card
• Energy cards

When trying to build custom dashboards, for example to manually visualize and calculate meter readings of a specific timeframe and to use that data in for example Jinja templates for visualizing anything, you'll quickly discover that you cannot use any variables from the energy-date-selection, because it won't expose anything.

I've created a dashboard that shows what this could be used for:

In my opinion this is missing core functionality that currently needs very wonky workarounds or the use of datetime helpers collecting unnecessary data or custom scripting that just builds around existing - but not-exposed data for this kind of front-end visualization.

I've found some related discussions, posts and feature requests that show the need of exposing these data points to avoid more custom trickery for seemingly existing functionality and showing what could be done if this wasn't an issue:

• https://community.home-assistant.io/t/wth-why-cant-we-utilise-the-energy-date-selection-card-like-an-input-date-time-helper/482069
• https://community.home-assistant.io/t/energy-date-selection-value/828333
• https://community.home-assistant.io/t/access-to-daily-energy-dashboard-values/475329/4
• https://www.reddit.com/r/homeassistant/comments/1kyksi2/energydateselection_with_utility_meter/
• https://community.home-assistant.io/t/a-simple-energy-entity-card-that-works-with-the-energy-date-selection/737582/5
• https://community.home-assistant.io/t/how-to-use-a-date-picker-card-for-a-time-start-end-input-for-graphcards/619237/7
• https://community.home-assistant.io/t/using-values-of-energy-management-in-dashboards/337876/8

[karwosts]

Imagine a custom cost calculation using the meters value at the start and end of the period.

Even if you had the value of the date selector, how would you get the value of the meter at those timestamps? Historical values are not available in templates either.

[danir-de]

There are already vanilla cards as well as HACS dashboard extensions that can query historical statistical data.
Displaying currently is mostly limited to graphs, but nothing would prevent just someone from creating a card that would just display a specific value. The problem is that there is no native way to use a template variable to extract specific values from energy-date-selection to use for parsing a cards configuration.

I wasn't aware that you cannot query statistical data by using templates, which is another problem altogether.

[karwosts]

I'd expect any custom cards should also be able to extract the value of the date selection for their own usage.

There just really isn't a concept in the ha core of a "front-end template", so there's no language to specify something like this. And we do not implement features that are only consumed by custom cards, anything we build has to make sense as a standalone feature.

[danir-de]

I understand that.
This feature request is meant to show the need of an official way to handle these things, that's also why I've linked multiple related threads, to raise awareness of the issue of home assistant lacking an official way, despite seemingly being able to do part of these things in very limited ways already.

As I understood reading the blog for years, Home Assistant wants to make dashboards more powerful and more easily usable for everyone via the GUI.
Not being able to use the provided tools like one would think it would be possible, when Home Assistant itself creates default dashboards with these features enabled (energy dashboard in this case), is leading to frustration for users.

If the topic of this discussion is not general enough I understand that, but I didn't find related discussions about this general issue on GitHub.