Self-consumption and battery protection: the priorities in the energy flow

A photovoltaic system is a good investment, but the real economy hides in self-consumption: the more of your own energy you use on site, the less you buy from the grid, and the less you export at an unattractive buy-back price.

The flow: Sun → Battery → Boiler → Grid → Consumption

HoumeOS watches the energy flow in real time and steers the surplus by priority, not at random:

1. First the battery — the surplus charges the accumulator so you have energy when the sun sets. 2. Then the boiler — with enough charge and the solar priority enabled, the remainder heats the hot water. 3. Finally the grid — only then is energy exported outward.

This is the same logic described in Solar surplus for hot water: instead of an expensive export and then an expensive buy-back, the home consumes its own energy in the right order.

"Self-consumption" in simple words

Imagine the panels give 5 kW at noon and the home draws 1 kW. The 4 kW difference is either exported to the grid at the buy-back price, or steered into the battery and the boiler. Every pointlessly exported kilowatt-hour is energy you buy back in the evening. That is why a sensible distribution of the surplus is the fastest way to raise the share of your own energy you actually use.

Battery protection comes first

Consumption optimization must not suck the accumulator to zero. When solar energy is short, the battery covers the deficit — but never below the emergency reserve (the minimum charge required for the specific chemistry and a long life). This threshold is not overridden by any economic optimization.

Why it matters: deep and frequent discharges shorten the battery's life. A long accumulator life is part of the saving — how big a battery you need and what reserve to set is covered in How big a battery and the MIN_SOC reserve.

What you see on the screen

The Energy screen shows the flow at a glance — production, consumption, battery charge, and how the surplus is being distributed right now. For a deeper analysis of production and net consumption, see Monitoring a solar system.

Realistic expectations

Self-consumption depends on the size of the panels, the battery, your tariffs and your habits. There is no universal number — there is a correct distribution, tuned to your home. That is why we start with a demonstration and site survey, to set the thresholds and priorities against your real production.