To integrate solar energy control into KNX ETS programming, you map your solar inverter’s output data to KNX group addresses, then use ETS logic functions or an external controller to switch loads based on available surplus. The key is treating solar production as a real-time input that drives automated load management rather than relying on manual switching or fixed schedules. The sections below break down exactly how to build, refine, and validate that logic step by step.
What KNX datapoints are needed to read solar inverter output?
To read solar inverter output in a KNX installation, you typically need datapoints for current power production (DPT 9.x, in watts or kilowatts), total energy yield (DPT 12.x or 13.x, in watt-hours), and grid feed-in or consumption values. Most inverters expose these via Modbus TCP or SunSpec, which a KNX gateway or controller then translates into group addresses readable by ETS.
The exact datapoints depend on your inverter brand and the gateway you use to bridge the protocol. Common values to map include:
- Instantaneous PV power output (W or kW)
- Net grid import or export power
- Battery state of charge, if a storage system is present
- Inverter status or fault flags
Once these values arrive on the KNX bus as group address telegrams, ETS can reference them in logic blocks or pass them to a controller for decision-making. Choosing the right DPT matters: using a floating-point type like DPT 9.002 for power values ensures the precision needed for meaningful threshold comparisons later in your control logic.
How does ETS logic link solar production to load switching?
ETS logic links solar production to load switching by comparing the live power production datapoint against predefined thresholds and triggering switch or dimming commands to group addresses when those thresholds are crossed. In practice, a logic block receives the current PV output value, evaluates it against a setpoint (for example, 1500 W surplus), and sends an ON telegram to a load group address when the condition is met.
The most straightforward implementation uses ETS logic functions such as comparators and AND gates. A comparator checks whether the solar surplus value exceeds the minimum power draw of a target load, such as a heat pump or dishwasher. An AND gate can add a secondary condition, such as time of day or occupancy, before the switch command is sent. This keeps the logic readable and maintainable inside ETS without requiring external scripting.
For more complex scenarios, many installers extend ETS with a dedicated controller. This is where a platform like xxter adds value: its scripting and trigger engine can handle sequential load switching, hysteresis timers, and priority hierarchies that would be cumbersome to build purely in ETS logic blocks.
What’s the difference between rule-based and dynamic solar control in KNX?
Rule-based solar control in KNX uses fixed thresholds and static conditions to trigger loads, while dynamic solar control continuously recalculates decisions based on real-time variables such as current surplus, weather forecasts, energy prices, and load priorities. Rule-based logic is simpler to configure in ETS but reacts only to what is happening now, whereas dynamic control anticipates what is likely to happen next.
A rule-based setup might say: if PV output exceeds 2 kW, switch on the pool pump. That works reliably on sunny days but cannot distinguish between a brief cloud shadow and a genuine drop in production. It also ignores whether electricity prices make it smarter to delay a load by thirty minutes.
Dynamic control introduces a feedback loop. The system reads forecast data, current grid tariffs, battery charge level, and household consumption simultaneously, then decides which loads to activate, defer, or shed. This approach consistently outperforms static rules in terms of self-consumption rate and cost savings, but it requires a controller capable of running continuous calculations rather than simple ETS comparator blocks.
How do you avoid backfeed conflicts when multiple loads compete for solar surplus?
To avoid backfeed conflicts when multiple loads compete for solar surplus in a KNX system, you assign each load a priority level and implement sequential switching logic that activates only one load at a time, waits for the system to stabilize, and then evaluates whether enough surplus remains to switch the next load. Without this sequencing, simultaneous switching can cause total consumption to overshoot available production and trigger unwanted grid import or inverter backfeed protection.
A practical approach is to define load tiers. High-priority loads like a heat pump or EV charger get first access to surplus. Medium-priority loads such as a washing machine or dishwasher activate only when the surplus after high-priority consumption still exceeds their minimum draw. Low-priority loads like a secondary water heater switch on last and are the first to be shed when production drops.
Hysteresis is equally important. If you switch a load on at exactly 1500 W surplus and off at exactly 1500 W, the system will oscillate with every minor cloud. Setting a wider band, for example on at 1800 W and off at 1200 W, prevents relay chatter and protects both the loads and the inverter from rapid cycling.
Can KNX solar control work with dynamic energy tariffs?
Yes, KNX solar control can work with dynamic energy tariffs by feeding real-time price data into the control logic alongside solar production values. When the grid tariff is high, the system prioritizes solar self-consumption aggressively. When the tariff is low or negative, it may defer loads or allow grid import instead of cycling batteries unnecessarily. This combination of solar surplus management and price-aware switching significantly improves the financial return of a KNX automation installation.
Implementing this requires a data source for tariff signals, typically an API feed from a dynamic pricing provider, and a controller that can ingest that data and expose it as a KNX datapoint or internal variable. Once the tariff value is available in the system, it becomes another input to your comparator logic, just like PV output or battery charge.
In 2026, dynamic tariff integration is increasingly relevant as more European markets move toward hourly or even quarter-hourly pricing. A KNX installation that ignores tariff signals leaves money on the table, particularly for high-draw loads like heat pumps and EV chargers that can tolerate flexible scheduling.
How do you test and validate solar control logic in ETS before going live?
To test and validate solar control logic in ETS before going live, use ETS’s group monitor to simulate input telegrams manually, observe whether the correct output commands are triggered, and verify that threshold conditions, hysteresis bands, and priority sequences behave as designed. Testing in simulation mode before connecting real loads prevents relay damage, unintended switching, and inverter faults caused by logic errors.
A structured validation process typically follows these steps:
- Send test values to the solar production group address and confirm that comparator outputs change state at the correct thresholds.
- Simulate rapid fluctuations to verify that hysteresis timers prevent oscillation.
- Test edge cases: zero production, maximum production, and values just above and below each threshold.
- Verify priority sequencing by simulating a surplus that is only sufficient for one load tier at a time.
After bench testing, a staged live commissioning approach is advisable. Connect one load first, monitor its behavior over several days across varying weather conditions, then add subsequent loads one at a time. This makes it far easier to isolate and correct any logic errors without the complexity of multiple simultaneous interactions.
How xxter Supports Professionals with KNX Solar Integration
xxter is built specifically for professional KNX installers who need to go beyond what ETS logic blocks alone can deliver. When it comes to solar energy control, the xxter controller acts as the central intelligence layer that reads inverter data, evaluates real-time conditions, and executes switching decisions with precision and flexibility.
Concretely, xxter helps professionals with solar integration in the following ways:
- The Smart Energy Manager (SEM) combines live PV production, dynamic energy tariffs, weather forecasts, and customer priorities to minimize grid consumption and reduce energy costs.
- The scripting and trigger engine handles priority-based load sequencing, hysteresis logic, and time-based conditions that would be complex to build in ETS alone.
- Native support for Modbus and BACnet means most inverter brands can be integrated without additional middleware.
There are no license fees or subscription costs, so the full feature set is available from day one on every installation. If you are working on a KNX project that includes solar energy management, explore what the xxter controller and Smart Energy Manager products can add to your setup, or get in touch with the xxter team to discuss your specific project requirements.