Home energy management: letting the house decide when to use power
A home energy management system watches the roof, the battery, the tariff and the weather, and moves the large loads to the right hour.
Solar panels, a battery, a heat pump and a wallbox each come with their own controller and their own app. Left alone, they compete: the battery fills itself at noon while the car waits, the heat pump runs at night on grid power. A home energy management system (HEMS) sits above them, reads the meter, the solar forecast and, if you have one, a dynamic tariff, and decides which device gets power when.
What a good HEMS actually does
- Surplus routing: sends solar surplus first to the loads that benefit most, often the car and the hot water tank, and only then to the battery and the grid.
- Forecasting: uses the weather forecast to leave room in the battery on a sunny morning, or to preheat the house before a cloudy afternoon.
- Tariff awareness: with a dynamic tariff, shifts flexible loads into the cheapest hours.
- Grid limits: keeps total consumption within the house connection or a feed-in limit, and responds to signals from the grid operator.
The interfaces that matter
A HEMS is only as good as its connections. Before buying any large device, check which of these it supports:
- SG Ready: a simple two-contact interface on heat pumps with four operating states, from blocked to forced on. Almost universal, but coarse.
- EEBus: a richer protocol for heat pumps, wallboxes and grid operator control, increasingly common in Europe.
- Modbus TCP and SunSpec: the workhorses for inverters, batteries and meters on the local network.
- Matter: the smart home standard backed by the major platforms; recent versions added device types for energy reporting, EV chargers, heat pumps, batteries and solar.
Germany: §14a EnWG
Since 2024, newly installed heat pumps and wallboxes above 4.2 kW in Germany must be controllable by the grid operator. In return for a reduced grid fee, the operator may temporarily dim them when the local grid is congested, but never below 4.2 kW. A HEMS that speaks to the operator's control box can then spread that limit intelligently across all devices instead of switching one off entirely.
Local control first
Many systems run their logic in a manufacturer's cloud. That is convenient, but it means your heating and charging depend on someone else's server and business model. Prefer systems that keep the control loop on a device in your home and use the internet only for forecasts and remote access. Ask what happens if the manufacturer's service ends, and whether you can read your data locally.
Choosing a system
Start from the devices you already own or plan to buy, and make a list of their interfaces. Then choose a HEMS that supports all of them natively. Open platforms such as Home Assistant or openHAB offer the widest device support for technically minded owners; installer systems from inverter and heat pump makers are simpler but often favour their own brand. Either way, ask the installer to document every connection and every rule, so the system remains understandable in five years.
Questions and answers
Do I need a home energy management system?
If you combine solar with at least one large flexible load, such as a heat pump or an electric car, a HEMS usually raises self-consumption noticeably. With solar alone, the inverter app is often enough.
What is SG Ready?
SG Ready is a simple interface on heat pumps with two switching contacts and four operating states. It lets a controller block the heat pump or ask it to run harder when power is plentiful.
Written by the sunaliv editorial team. Figures are typical ranges for Central Europe unless stated otherwise and reflect the state of knowledge in October 2026. Spotted an error? Write to info@nextao.de and we will correct it openly.
