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Heat Pump & Hot Water

Your hot water tank is a battery, one you never had to buy. Franzl fills it with solar power, and keeps it within your comfort limits.

What Franzl does

Heat is the most rewarding storage in the house: a hot water tank heated to 55°C at midday with surplus power saves grid kilowatt-hours in the evening, with no battery at all. Franzl turns this into an automatic process:

• Heating up on surplus: If there's solar power left over (after the loads that matter more to you), Franzl heats water, the heat pump, or the pool toward your comfort maximum, never past it.
• Holding back when power is expensive: Within your comfort band, Franzl puts the temperature to work: pre-heating when it's cheap, letting it drop when it's not. Your band sets the limits, Franzl picks the timing.
• You say what, Franzl decides when: "Heat now" works anytime: one tap in the app, and your request beats the plan.

Schedules a human can understand

For heat pumps and AC, you set day/night segments with temperature bands: no expert-device menu, just a hand-drawn 24-hour bar with presets. Hot water and pool need just a single band ("between 45°C and 55°C").

Safety is non-negotiable

Two limits are hard-wired into Franzl and can never be undercut by any optimization: frost protection for heating and AC, and legionella protection for hot water. A weekly 60°C legionella cycle can be switched on if your device doesn't already handle it itself; many modern devices do, in which case Franzl doesn't interfere.

Will this work with my heat pump?

The honest answer: it depends on the model, which is exactly what the device database is for. Franzl controls some heat pumps directly (local interface), many through SG-Ready contacts, and some read-only. A simple immersion heater on a switchable outlet works too, by the way, as a surplus heater with a bound temperature sensor.