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Renewable energy

The ideal energy home

Photovoltaics, heat pump, EV and a dynamic electricity tariff — designed as one system, not four separate appliances.

The hardware for a largely self-sufficient family home has been off the shelf for years: PV modules, battery storage, a heat pump, a wallbox. What's usually missing isn't technology — it's integration. Only when every component talks to the others, and one central logic decides where each kilowatt-hour goes, do separate appliances become a system that cuts costs instead of merely generating electricity.

This page describes a reference architecture: which components belong in such a house, which software connects them, and which strategies the system uses to weigh sunshine, electricity price and demand against each other. That integration work is exactly the part softleb takes on.

Where does a kilowatt-hour go?

The heart of the system is a priority cascade: for every kilowatt-hour generated, the energy management decides in real time where it creates the most value. The order below is the sunny-day default — it is continuously re-sorted against electricity price, weather forecast and charge levels.

PV generation on the roof

  1. Household consumption

    Base load and running appliances are covered directly. The self-consumed kilowatt-hour is the most valuable one in the whole system: it replaces grid electricity at the full retail rate instead of earning only the feed-in tariff.

  2. Heat & hot water

    The SG-Ready heat pump uses surplus to overheat the hot-water tank and pre-heat the house — heat is the cheapest storage in the building. A continuously modulated heating element mops up even the smallest remaining surplus as the final stage.

  3. Battery storage

    Whatever house and heat don't absorb fills the battery for the evening and night. If tomorrow's forecast is sunny, the battery may discharge deeper tonight — the forecast controls the reserve.

  4. The EV

    With the car at home, surplus charging modulates the charging power second by second between roughly 1.4 and 11 kW — single-phase under thin clouds, three-phase in full sun. Targets like “80% by 7 a.m.” remain guaranteed throughout.

  5. Feed-in

    Only the remainder goes to the grid. With variable feed-in remuneration via direct marketing, it pays to shift feed-in from the battery into the evening price peak instead of selling at midday's daily low.

… and only then the public grid

With a dynamic supply tariff the cascade inverts at night: in the cheapest hours the grid charges battery and car — and when exchange prices go negative, consuming actually earns money.

The components

The bill of materials for such a house — with what really matters about each component for integration: open interfaces and local controllability. The products named are proven examples, not requirements.

The software that connects it all

The intelligence of the house is a software stack of proven open-source building blocks — read top to bottom: from the dashboard the residents see, down to the small computer in the basement that runs it all.

What the residents see

  1. Interface & dashboards

    One glance at the phone shows generation, storage level, charging power and the current exchange price. Operating the system mostly means one thing: setting targets — the system decides the rest.

  2. Decision logic & automations

    Home Assistant is the control centre: PV forecast, price signal, charge levels and weather data converge here, and this is where the automations live — overheating the tank, boosting the heat pump, applying §14a dimming signals without anyone noticing.

  3. Charge control

    EVCC is the specialised controller for the car: surplus charging with second-by-second tracking, price-optimised target charging, phase switching, battery prioritisation. It supports well over a hundred wallboxes and the APIs of most vehicles.

    • EVCC
    • Target charging
    • PV & price modes

  4. Protocols & data bus

    The devices speak different languages — Modbus TCP, MQTT, OCPP, SG-Ready contacts, vendor REST APIs. An MQTT broker as the central data bus decouples the components; every control loop runs entirely locally.

  5. Foundation & operations

    A frugal small computer carries the whole system, buffered by a UPS. Readings land in a time-series database for long-term analysis; remote access runs over VPN, the configuration is versioned, backups run automatically.

… down to the hardware

Local-first as a principle: every control loop runs inside the house. Cloud services only supply auxiliary data — prices, forecasts, the vehicle's state of charge — and their outage slows the system down instead of stopping it.

Operating strategies

Only integration makes these strategies possible — each one cuts costs or raises self-consumption, and together they are the difference between a PV installation and an energy system.

Surplus charging

The car charges exclusively on electricity that would otherwise be exported. The control follows the cloud cover second by second, modulating between 1.4 and 11 kW — and a target still guarantees a full battery in the morning.

Heat instead of feed-in

Overheat the 300-litre tank to 60 °C at noon instead of exporting for a few cents: the hot-water tank is the cheapest kilowatt-hour of storage in the house, shifting PV energy into the evening's shower and heating.

Price-led charging

If the PV forecast is weak, battery and car charge in the cheapest night hours of the dynamic tariff. When exchange prices go negative, the market pays for consumption — the system takes such hours along automatically.

Intelligent feed-in

With variable remuneration, not every exported kilowatt-hour is worth the same. The battery holds energy back and feeds into the evening peak on purpose — direct marketing turns the PV system into a small power plant on the market.

Forecast-based planning

PV-yield and load forecasts decide each morning how the day is run: reserve in the battery or free discharge, shifting the heat pump into the sunny midday hours, placing the car's charging window.

Pricing in §14a EnWG

Heat pump and wallbox registered as controllable loads noticeably lower the grid fees. The operator's rare dimming signals are applied automatically by the energy management — with a battery and thermal mass, nobody in the house notices.

What such a system achieves

Typical target figures for a family home with 10–15 kWp, storage, heat pump and EV — the exact numbers depend on load profile, roof and location.

60–80%
self-sufficiency over the year — the share of consumption covered by PV and storage
1.4–11 kW
control range of surplus charging thanks to 1-/3-phase switching
COP 3–5
the heat pump turns one kilowatt-hour of electricity into three to five kilowatt-hours of heat
15 min
resolution of the exchange prices that charging, storing and feed-in react to

What softleb takes on

softleb plans and builds the integration — vendor-independent, on open standards, coordinated with your electrical and heating contractors.

For clarity: electrical and heating installation belongs in the hands of certified contractors. softleb delivers concept, software and integration — working closely with your installer throughout.

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