[FR]Slow loading when using template sensors (history) with aggregation: last

[ElianST]

Please describe the idea

Hi,

I noticed a performance difference when using sensors that only provide recorder history instead of long-term statistics.

Utility Meter sensors in Home Assistant use Long-Term Statistics and load almost instantly in the header of the Statistics Graph Chart Card when using the preset last instant.

However, when I use a Template Sensor helper, the card takes noticeably longer to load. Template sensors only expose recorder history, so I assume the card needs to process a much larger dataset.

My use case is calculating my own energy consumption with a template:

consumption = production - returned_to_grid

This works correctly, but when this sensor is used in the card header (for example daily or monthly values with aggregation: last), loading the card becomes slower compared to sensors that use statistics.

Since template sensors cannot provide long-term statistics, I was wondering if the card could potentially optimize history-based sensors when using aggregation: last. For example by:

• only requesting the last datapoint of the selected period
• reducing the amount of history that needs to be processed
• or caching the result

Utility meter sensors load almost instantly, so it would be great if history-only sensors could behave similarly in this case.

Loading takes 10 to 20 seconds everytime:

type: custom:statistics-graph-chart-card
card_header: Maandverbruik
card_background_color: rgba(36, 37, 41, 0.3)
card_border: false
show_tooltip_total: false
animate_graph: true
stacked: true
points_per_hour: 1
height: 300
show_full_period: true
x_grid_style: long-dash
y_grid_style: long-dash
show_date_picker: true
date_picker_group: "1"
date_picker_modes:
  - month
state_layout: horizontal
group_by: date
entities:
  - entity: sensor.dagverbruik_p1_import
    statistic_id: null
    name: Import
    color: "#ff3cdd"
    graph_type: bar
    aggregate_func: last
    state_size: 24px
    show_trend_icon: false
    primary_state_as: sum
    name_position: below
    state_color: "#ffffff"
  - entity: sensor.dagverbruik_p1_export
    statistic_id: null
    name: Export
    color: "#36ec22"
    graph_type: bar
    aggregate_func: last
    icon_size: 22px
    state_size: 24px
    invert: true
    show_trend_icon: false
    primary_state_as: sum
    name_position: below
    state_color: "#ffffff"
    align_state: center
  - entity: sensor.eigenverbruik_maand
    statistic_id: null
    name: Eigen verbruik
    color: "#04a2ff"
    graph_type: bar
    aggregate_func: last
    icon_size: 22px
    state_size: 24px
    invert: true
    show_trend_icon: false
    primary_state_as: last
    name_position: below
    state_color: "#ffffff"
    align_state: right
    points_per_hour: 1
    show_graph: false
    show_line: false
    show_fill: false
annotations: []
grid_options:
  columns: 15
  rows: auto