Solar production is not automatically your electricity bill saving. Useful monitoring separates production, grid imports and exports. This researched guide covers data integration for an already correctly installed system. It does not explain mains electrical work, changing export limits, or authorise installation across different countries.
1. Choose the question before the sensor
| Your question | Data you need |
|---|---|
| How much is the system producing now? | Current active power in W |
| How much did it generate today? | Energy in Wh or kWh over the period |
| How much do I use myself? | Production and export readings covering matching periods |
| How much money does it save? | Self-consumption, your actual import tariff and any export payment |
An inverter alone normally cannot see every household load. Without additional measurement at the appropriate point, its production reading cannot prove self-consumption. Consumption measured at one socket is not total household consumption either.
2. A concrete local option: APsystems EZ1
Home Assistant has an existing APsystems integration for EZ1 microinverters. Its documentation covers local polling, current power and cumulative production. This does not promise support for every APsystems range. Check the exact model before buying.
According to the documentation, enable the local API and select continuous local operation. Setup uses the manufacturer app over Bluetooth, depending on the model; cloud registration and local mode can be related. Record the initial state and check the documented consequences before changing an existing association. Then add APsystems in Home Assistant under Settings → Devices & services → Add integration.
Start with reading data only. The integration also exposes switching and output-limit controls, but a production chart does not need them. Leave them unchanged. The documentation also warns about wear from excessively frequent limit changes on certain older hardware. Monitoring is not a reason to introduce those writes.
3. An alternative for compatible Hoymiles models: OpenDTU
OpenDTU is an existing open-source project for communicating with supported Hoymiles inverters. It offers MQTT and Home Assistant discovery, among other features. This is an established option, so a separate custom cloud connector is not needed just to create a chart.
For example, the OpenDTU inverter overview lists HM-800-2T with NRF24L01+ and HMS-800-2T with CMT2300A. It explicitly excludes models with integrated Wi-Fi identified by a W in the name, such as HMS-xxxW. Resolve these differences before buying a DTU.
Before buying, check the current compatibility list, exact inverter family and required radio hardware. The Hoymiles brand name alone is insufficient. Changing a dashboard card cannot make a DTU with the wrong radio generation compatible. For beginners, a documented, compatible and maintained setup matters more than an unclear low-cost kit. We make no fixed price or availability claims here.
4. Use the correct units in the Energy dashboard
Add production energy as a solar source in the energy settings. Select an appropriate energy entity, not instantaneous power by mistake. The Home Assistant solar documentation explains existing integration and metering options. Work involving distribution boards or current transformers requires qualified expertise.
W measures power at a moment. kWh measures energy over time. An illustrative calculation, not a measured yield: a constant 400 W for two hours gives 0.8 kWh. With changing sunlight, actual power must be integrated over time. A single midday reading must not be extrapolated over a whole day.
Check units, device class, statistics support and counter behaviour against the integration documentation. A daily counter resets; a lifetime counter behaves differently. Do not blindly change metadata just to make a sensor appear in a list. If only power is available, use an appropriate time-integration method and understand its sampling and outage behaviour.
5. Validate the data before decorating the dashboard
- Compare several current readings with the local device display or manufacturer app, allowing for different update intervals.
- Check a complete day transition: do the time zone and counter reset behave correctly?
- Observe the state during a device or network outage. Unavailable does not mean a measured zero watts.
- After a normal restart, check that cumulative energy continues correctly without artificial spikes.
- Record gaps in reports instead of inventing missing production readings.
6. Assess self-consumption and automation realistically
Without a battery and using matching measurement boundaries, self-consumed PV energy can be approximated as production minus the corresponding exported energy. Batteries, other generation sources and differing time intervals change the calculation. Multiplying daily production by the electricity tariff is therefore often not the actual saving.
Begin with a notification when production plausibly persists, rather than automatically changing inverter settings. Later, controlled loads need minimum run times, hysteresis and defined behaviour when data is missing. Safety-related loads must not depend on an incomplete solar chart.
Conclusion: establish a compatible, preferably local data connection; verify units and measurement boundaries; then analyse the result. A simple chart of reliable kWh is more useful than an elaborate dashboard with incorrectly calculated savings. Prices, export rules and payments require separate checks for the relevant country.