How to use solar surplus for hot water

A photovoltaic system produces the most energy around midday — exactly when there is often nobody home to use it. Without management, the surplus simply flows to the grid at a buy-back price lower than the price you pay for electricity. The whole point of energy automation is to keep as much of your own energy as possible.

Where the surplus goes

• Charging the home battery — up to the configured minimum charge (MIN_SOC).
• Heating the water tank — hot water is a cheap, slow buffer.
• Running flexible-appliance loads — washing machine, dishwasher, air conditioning.
• Only the remainder is exported to the grid.

The distribution priority

HoumeOS watches production, consumption and battery charge in real time and distributes along a fixed priority: first the battery, then the water heater (once there is enough charge and solar priority is enabled), and finally export. The battery reserve is absolute — the system never drains it below the configured minimum, so you keep lights and internet in the evening.

Why a water heater is a good battery

A kilowatt-hour invested in hot water costs the same as a kilowatt-hour invested in an expensive battery — except the "storage" is nearly free, because you already own the tank. That is why diverting surplus to hot water is the fastest way to raise your self-consumption without new capital.

What to expect

The real effect depends on the property, but in a typical house with an 8 kWp system and a water heater, self-consumption rises noticeably and the bill falls. What matters is testing the rules on live data — which is why we start with a demonstration and a site survey, not with blind preset configurations.