SG-Ready (Smart Grid Ready) is a standardised heat pump control interface defined by the German Heat Pump Association (BWP) in 2012. Two switching contacts encode four operating states — from a temporary block to forced operation — letting utilities and home energy managers shift heat pump operation toward cheap or surplus electricity. Germany's BEG subsidy requires grid-responsive capability of this kind.
What does the SG-Ready label mean?
SG-Ready is a certification label of the German Heat Pump Association (Bundesverband Wärmepumpe, BWP), introduced in 2012 together with leading manufacturers. It confirms that a heat pump exposes a standardised control interface: two potential-free switching contacts whose combinations select four defined operating states.
The design is deliberately low-tech — plain relay logic rather than a data protocol — which is exactly why it spread across the industry. Any energy management system, PV inverter or utility ripple-control receiver that can close a relay can steer any SG-Ready heat pump, regardless of brand.
How do the four SG-Ready operating states work?
The two contacts form a binary code, and every certified unit interprets it identically:
| State | Contacts | Meaning |
|---|---|---|
| 1 — Blocked | 1:0 | Operation paused for a limited period; heat supply must remain assured |
| 2 — Normal | 0:0 | Efficient automatic operation (default) |
| 3 — Recommended on | 0:1 | Cheap or surplus electricity available: raise setpoints, charge storage |
| 4 — Forced on | 1:1 | Unit is ordered to run, within its protection limits |
State 1 mirrors the classic German utility lock tariffs, which allowed at most three two-hour blocks per day — the building's heat supply may never be endangered. State 3 is the workhorse in practice: the controller typically raises buffer tank and hot water setpoints by 5–10 K to soak up the favourable electricity.
Why do subsidies and grid rules demand SG-Ready?
Germany's BEG heating grant (KfW programme 458) only funds heat pumps with a grid-responsive interface, and SG-Ready is the accepted standard implementation. In parallel, §14a of the German Energy Industry Act treats new heat pumps as controllable consumption devices: the grid operator may briefly dim them to a guaranteed minimum of 4.2 kW — never fully off — and the owner receives reduced network charges in return.
The motive is scale. EHPA counted 2.88 million heat pumps sold in Europe in 2025 alone (+13%), and millions of compressors switching with the weather are either a grid problem or, coordinated through interfaces like SG-Ready, a grid resource.
How does SG-Ready raise PV self-consumption?
A home energy manager watches the PV surplus and closes the state 3 contact when export begins. The heat pump then overheats its thermal storage: a 300-litre cylinder raised by 10 K banks about 3.5 kWh of heat — storage capacity at a fraction of battery cost per kWh. In the evening the stored heat displaces grid electricity.
The pairing is strongest where generation and heat meet: a PVT hybrid collector field produces the surplus electricity while pre-warming domestic hot water, and the SG-Ready signal times the compressor to run exactly when the roof produces.
Is SG-Ready used outside Germany?
Yes — the interface travelled with German-market heat pumps and is now commonly specified across Central and Northern Europe, and heat pump tenders increasingly list it by name. The EU's planned rescaled heating energy label adds a smart-readiness pictogram (consultation closed January 2026; check the current adoption status). Digital protocols such as EEBUS offer richer control — modulating power in watts rather than four coarse states — but they complement rather than replace the relay interface, which remains the lowest common denominator every device understands.
Frequently asked questions
Is SG-Ready mandatory for heat pumps?
There is no EU-wide legal obligation, but Germany's BEG subsidy requires grid-responsive capability for funded heat pumps, and German grid rules require new units to be controllable. Commercially, SG-Ready is now a default specification item across much of Europe.
Can the utility switch my heat pump off completely via SG-Ready?
No. State 1 only pauses operation for limited periods and the heat supply must remain assured; under German §14a rules the grid operator may only dim consumption to a guaranteed minimum, not disconnect it. Comfort protection stays with the heat pump controller.
Do I need SG-Ready to use my solar PV surplus for heating?
It is the simplest proven route: the inverter or energy manager closes the recommended-on contact and the heat pump charges its storage with surplus power. Without it you need brand-specific digital integrations, which not every inverter and heat pump pair supports.
What is the difference between SG-Ready and §14a EnWG control?
SG-Ready is a voluntary industry interface standard defining how a heat pump receives signals; §14a is the German legal framework defining when a grid operator may reduce the power of controllable devices and what fee reductions the owner gets. In practice the §14a control command often arrives through the SG-Ready contacts.