Failed to generate forecast: No historical data available for sensor

[F21]

System Health details

System Information

version	core-2026.1.0
installation_type	Home Assistant Container
dev	false
hassio	false
docker	true
container_arch	amd64
user	root
virtualenv	false
python_version	3.13.11
os_name	Linux
os_version	6.6.87.2-microsoft-standard-WSL2
arch	x86_64
timezone	Australia/Melbourne
config_dir	/config

Home Assistant Cloud

logged_in	false
can_reach_cert_server	ok
can_reach_cloud_auth	ok
can_reach_cloud	ok

HAEO

error	failed to load: unknown

Dashboards

dashboards	2
resources	0
views	0
mode	storage

Network Configuration

adapters	lo (disabled), eth0 (enabled, default, auto)
ipv4_addresses	lo (127.0.0.1/8), eth0 (172.18.0.2/16)
ipv6_addresses	lo (::1/128), eth0 ()
announce_addresses	172.18.0.2

Recorder

oldest_recorder_run	January 9, 2026 at 2:11 AM
current_recorder_run	January 16, 2026 at 1:48 PM
estimated_db_size	46.80 MiB
database_engine	sqlite
database_version	3.49.2

Checklist

• I have enabled debug logging for my installation.
• I have filled out the issue template to the best of my ability.
• This issue only contains 1 issue (if you have multiple issues, open one issue for each issue).
• This issue is not a duplicate issue of any previous issues.

Describe the issue

I am using HAFO to estimate a sensor for my eletrical load. The sensor is derived from another sensor using a template and works correctly.

This is the configuration for that sensor in my configuration.yaml:

template:
  - sensor:
    - name: "House Load"
      state: "{{ state_attr('sensor.homekit_homekit_gw_homekit_no_serial', 'load') }}"
      unit_of_measurement: "W"

I can see that it generates the correct data and it is visible when plotted in history:

I have HAFO set to use 3 days for history and to use the house load sensor as its source:

But it doesn't seem to produce any data:

In my logs I see the following:

home-assistant  | 2026-01-16 04:13:46.295 INFO (MainThread) [custom_components.hafo] Setting up forecaster: House Load
home-assistant  | 2026-01-16 04:13:46.307 WARNING (MainThread) [custom_components.hafo.forecasters.historical_shift] Failed to generate forecast: No historical data available for sensor.house_load
home-assistant  | 2026-01-16 04:13:46.307 DEBUG (MainThread) [custom_components.hafo.forecasters.historical_shift] Finished fetching hafo_01KF2G4RDQ7ARWNN3BH3DCF7MZ data in 0.012 seconds (success: True)
home-assistant  | 2026-01-16 04:13:46.307 INFO (MainThread) [homeassistant.components.sensor] Setting up hafo.sensor
home-assistant  | 2026-01-16 04:13:46.307 INFO (MainThread) [homeassistant.helpers.entity_registry] Registered new sensor.hafo entity: sensor.house_load_forecast
home-assistant  | 2026-01-16 04:13:46.308 INFO (MainThread) [custom_components.hafo] Forecaster setup complete: House Load

Reproduction steps

1. Create a sensor derived from another sensor
2. Set up HAFO to use that sensor as the source.
3. HAFO forecast sensor is unknown and does not produce any data.

Debug logs

See: https://gist.github.com/F21/0e1ef9d757e2d29ec53fa8b3e885d4f6

[deverton]

Sensors used by HAFO for forecast look like they need to have what Home Assistant calls "long term statistics". To get that for your template sensor you need to set the state_class to one of the settings that allows for long term stats.

See https://developers.home-assistant.io/docs/core/entity/sensor/#long-term-statistics

Long-term Statistics

Home Assistant has support for storing sensors as long-term statistics if the entity has the right properties. To opt-in for statistics, the sensor must have state_class set to one of the valid state classes: SensorStateClass.MEASUREMENT, SensorStateClass.TOTAL or SensorStateClass.TOTAL_INCREASING. For certain device classes, the unit of the statistics is normalized to for example make it possible to plot several sensors in a single graph.