Forecast Solar in Home Assistant: Predicting Your Solar Production with Precision
If you have solar panels connected to your home, one of the most useful things you can add to Home Assistant is production forecasting. Knowing how much energy your system is expected to generate over the next few hours or days makes it much easier to optimise automations, reduce electricity costs, and intelligently schedule high-consumption devices.
That is exactly what the official Forecast Solar integration documentation provides.
The Home Assistant Forecast Solar integration connects your Home Assistant installation to the Forecast.Solar service and delivers highly useful estimated solar production data based on:
- Your panel orientation
- Panel tilt angle
- Installed peak power
- Geographic location
- Weather forecast data
- Solar irradiance models
This gives you a reliable estimate of how much electricity your solar installation will produce throughout the day.
In this article, we will look at how Forecast Solar works, explain its key components, and build a practical automation that uses the forecast to run appliances when solar production is expected to be high.
What is Forecast Solar?
Forecast Solar is a cloud-based prediction service designed specifically for photovoltaic systems.
It calculates expected solar generation using weather forecasting models combined with the physical characteristics of your solar installation.
Once integrated into Home Assistant, it creates sensors that allow your automations, dashboards, and energy management logic to react based on predicted production rather than only current measurements.
This is particularly valuable if you want to:
- Run appliances when excess solar energy is expected
- Charge EVs during peak production
- Preheat water when generation is high
- Reduce grid imports
- Improve self-consumption of your solar energy
For households with dynamic electricity pricing, combining Forecast Solar with spot pricing sensors can create very powerful automations.
Why Forecasting Matters
Without forecasting, automations react only to current production.
For example, if your inverter currently reports 4.5 kW production, that tells you what is happening right now — but not whether clouds are about to reduce output in 15 minutes.
Forecast Solar solves this by giving your automations future context.
Instead of reacting blindly, Home Assistant can make smarter decisions such as:
“The forecast predicts 12 kWh production today, so it is worth scheduling the water heater at 11:00.”
This predictive capability makes Home Assistant feel significantly more intelligent.
Components Created by the Integration
When you configure Forecast Solar, Home Assistant creates several useful sensors.
Estimated Energy Production Today
This sensor reports the total expected production for the current day in kWh.
Example:
sensor.forecast_solar_energy_todayPossible value:
18.4This means your system is expected to generate 18.4 kWh today.
This is ideal for deciding whether to schedule large loads.
Estimated Energy Production Tomorrow
This sensor provides the forecast for the following day.
Example:
sensor.forecast_solar_energy_tomorrowUseful for:
- Planning EV charging overnight
- Deciding whether to postpone appliance loads
- Preparing heating schedules
Estimated Power Production Now
This sensor predicts current production in W.
Example:
sensor.forecast_solar_power_nowThis is useful for real-time automation triggers.
Estimated Peak Production Time
Some configurations expose information about when production is expected to peak.
This allows automations to target the best production window.
For example:
- Dishwasher start
- Washing machine
- Domestic hot water heating
- Battery charging
Remaining Energy Today
One of the most practical sensors.
It estimates how much production is still expected for the rest of the day.
Example:
sensor.forecast_solar_remaining_todayThis is perfect for late-day decisions.
Configuring Forecast Solar
The integration is added directly through the Home Assistant UI.
You will need:
- Your solar installation location
- Panel azimuth
- Panel tilt
- Installed peak power in kW
- Optional inverter efficiency adjustments
Panel Orientation Explained
This is often the most confusing part.
Azimuth defines compass direction:
- 0° = North
- 90° = East
- 180° = South
- 270° = West
For most European rooftop systems:
- South-facing: 180°
- South-east: 135°
- South-west: 225°
Tilt is the roof angle relative to horizontal.
Typical European roofs are often between 25–45°.
Entering accurate values significantly improves forecast precision.
Building a Useful Automation
A great practical example is automatically starting your water heater when enough solar production is forecast.
This helps convert excess generation into stored thermal energy rather than exporting it to the grid.
Automation Logic
The automation should:
- Run every morning at 08:00
- Check if forecasted production exceeds 10 kWh
- Turn on the water heater
- Only run if the outdoor temperature is below 18°C
The temperature condition ensures hot water heating is prioritised during cooler periods when demand is higher.
YAML Automation Example
alias: Heat Water When Solar Production Is High
description: Uses Forecast Solar prediction to heat water efficiently
trigger:
- platform: time
at: "08:00:00"
condition:
- condition: numeric_state
entity_id: sensor.forecast_solar_energy_today
above: 10
- condition: numeric_state
entity_id: sensor.outdoor_temperature
below: 18
action:
- service: switch.turn_on
target:
entity_id: switch.water_heater
- service: notify.mobile_app_phone
data:
title: Solar Automation
message: >
Water heater started.
Forecast production today is
{{ states('sensor.forecast_solar_energy_today') }} kWh.
mode: singleWhy This Automation Works
This automation intelligently combines weather-based solar forecasting with environmental conditions.
If the forecast predicts strong production and the outdoor temperature is relatively low, Home Assistant proactively heats water.
Benefits include:
- Better solar self-consumption
- Reduced grid electricity usage
- Lower electricity costs
- More efficient use of renewable energy
Combining Forecast Solar with Other Integrations
Forecast Solar becomes even more powerful when combined with other Home Assistant integrations.
Nord Pool
If you use Nord Pool integration, you can decide whether to:
- Use solar production
- Buy cheap electricity
- Delay loads
This is particularly useful in Europe where dynamic pricing is increasingly common.
EV Charging
Forecast data can help schedule EV charging when:
- Solar production exceeds expected household load
- Electricity prices are low
- Battery charging can be delayed
For EV owners, this is one of the best automation use cases.
Battery Storage
If you have home battery storage, Forecast Solar can help determine:
- When to reserve battery capacity
- When to discharge
- When to charge from grid power
Dashboard Visualisation
Forecast Solar data looks excellent on a Home Assistant dashboard.
Recommended cards include:
- Energy forecast gauge
- Remaining production graph
- Daily forecast comparison
- Current vs predicted production
A simple energy dashboard showing expected daily kWh can provide excellent visibility into your system performance.
Accuracy Considerations
Forecast Solar is very good, but no forecast is perfect.
Accuracy depends on:
- Correct panel configuration
- Local weather variability
- Cloud cover prediction accuracy
- Shading effects not modelled by the service
The best approach is to monitor actual production for a few weeks and adjust panel parameters if needed.
Final Thoughts
Forecast Solar is one of the most practical integrations available for solar-powered Home Assistant users.
It transforms your automations from reactive to predictive.
Instead of simply responding to what your solar system is doing right now, Home Assistant can make intelligent decisions based on what your system is expected to do next.
If you already use Home Assistant’s energy dashboard and have rooftop solar, this integration is absolutely worth installing.
Combined with smart automations, it can help maximise self-consumption, lower energy costs, and make your home considerably smarter.
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