Introduction: SG Ready heat pumps respond to grid signals through a few controller inputs, and those four states explain what load shifting really does to heating and hot water.
A heat pump wearing an SG Ready label is usually sold as a "smart grid" appliance, which sounds like the machine somehow optimises itself. What the label actually describes is narrower and far more useful: a defined way for an outside signal — from a utility, a home energy management system, or a photovoltaic controller — to reach the heat pump controller and change what it does next. Once you separate that input layer from the heat pump's own operating logic, the four signal states stop being marketing language and become a simple map: one state pauses the machine, one lets it run normally, and two push it to store extra heat while electricity is cheap or abundant. this guide walks through that map, then looks at why receiving a signal is a different thing from paying less.
What the SG Ready label adds to a heat pump controller
The SG Ready label comes from BWP, the German heat pump association, and its purpose is interoperability. Before it existed, a "grid-ready" heat pump meant whatever the manufacturer decided it meant, so a utility could not send the same instruction to two brands and expect the same result. SG Ready fixes that by defining a small, standard input interface — in practice a pair of digital contacts on the controller — that any grid operator or energy management device can switch. The two contacts read together produce four combinations, and those four combinations are the four signal states. Nothing in this layer touches the refrigerant circuit, the compressor, or the hydraulic design; it only changes the instruction the controller is currently following. That distinction matters because it explains what a heat pump with SG Ready can and cannot do. Without a defined input, a "smart" heat pump is really just following its own clock, its outdoor-temperature curve, and its own sensors. With the input, part of the decision about *when* to run moves outward — to a utility running a demand-response programme, or to a home controller watching spot prices or rooftop solar output. The wider grid world uses protocols such as OpenADR to automate exactly this exchange, sending price and event signals that buildings respond to without anyone touching a dial. SG Ready is a heat-pump-sized version of the same idea: a listening port rather than a new efficiency class. On a machine like the Green Power R290 monobloc, this port sits alongside Wi-Fi control and a 5-inch colour touchscreen that reports energy consumption by day, month, and year. That combination is genuinely practical, because the screen is where a household can see what the signals actually did to running hours and consumption, rather than guessing from a monthly bill.
How the four signal states change heating, hot water, and storage behavior
The four states form a scale from "pause" to "run hard now," and each one maps to a different operating behaviour rather than a different efficiency level. The standard BWP definitions read roughly as follows:
- State 1 — blocked. The grid asks the heat pump to stop drawing power, usually during a peak or a grid bottleneck. The controller suspends space heating and hot water production, keeping only frost protection and safety functions alive so the building and the water circuit stay protected.
- State 2 — normal operation. No special request is active. The heat pump follows its own schedule, weather-compensated flow temperature, and hot water setpoint exactly as it would without any grid connection, which is where most units spend most of their time.
- State 3 — recommended boost. The grid signals favourable conditions, such as surplus renewable output or a low spot price. The controller can lift the buffer tank or cylinder setpoint a few degrees and let the heat pump charge storage beyond its usual target.
- State 4 — mandatory boost. A stronger "start now" request. The controller drives the heat pump toward higher storage temperatures to absorb as much electricity as the system can reasonably take, still within its own safety and operating limits.
What makes states 3 and 4 meaningful is thermal storage, not the signal itself. A hot water cylinder is the cheapest storage a house owns: it is stratified, it holds temperature for hours, and nobody notices a tank sitting at 55 °C instead of 48 °C. A buffer tank on the heating circuit does the same job for space heating, and a concrete slab or underfloor loop can absorb even more energy slowly. A house with a large cylinder and a buffer can shift a useful block of operation; a house with a small cylinder and no buffer has very little to work with. How far setpoints move, how long a boost lasts, and whether state 1 blocks hot water as well as heating are all controller settings, so two SG Ready heat pumps can behave quite differently in the same house.
Why SG Ready load shifting is not the same as a guaranteed electricity saving
The signal is a message about the grid, not a message about your bill. For load shifting to turn into money, two things have to be true at once: the price you actually pay has to move in a way that tracks the signal, and the heat you store has to displace heat you would otherwise have bought at a higher price. On a flat-rate tariff, states 3 and 4 mostly shuffle consumption around the clock — the kilowatt-hours are largely the same, minus a little extra standing loss from the hotter tank. On a dynamic tariff, or with rooftop solar, the same states can genuinely move consumption into cheap or self-generated hours. There is also a small efficiency trade-off worth understanding. Charging a cylinder to a higher temperature means the heat pump runs at a higher condensing temperature during those hours, which lowers its coefficient of performance for that period. That is usually acceptable, because the goal is buying cheaper kilowatt-hours rather than fewer of them. Heat losses from a hotter tank and a warmer slab rise slightly too, so a boost that is far larger than the building can absorb is wasted. The US Department of Energy frames this whole area as load flexibility, and its value depends on controls, envelope quality, and available storage — not on the presence of a badge on the appliance. That is the honest way to read SG Ready on a product like the Green Power R290 monobloc: it is a control feature that lets the heat pump respond to grid signals, and the touchscreen's daily, monthly, and yearly consumption display is what turns that into something a household can actually evaluate. Whether it lowers a bill depends on the utility's signals, the installed controller configuration, and the tariff in force. Two identical heat pumps on two different tariffs can produce two very different results.
Conclusion
SG Ready is best understood as a listening interface with four defined states: block, normal, recommended boost, and mandatory boost. What those states do to a house depends on how much thermal storage exists and how the installer configured the controller, and what they do to a bill depends on whether the electricity price actually varies with the signal. Readers comparing heat pumps should therefore check three things rather than one: that the controller exposes the SG Ready inputs, that the system has enough cylinder or buffer volume to make shifting worthwhile, and that a tariff or solar setup exists to reward the shift. Everything else is potential rather than performance.
FAQ
Q: What do the four SG Ready signal states usually mean for a heat pump?
A: They form a scale from pause to boost. State 1 blocks the heat pump from drawing power while keeping frost protection active, state 2 is ordinary operation with no special request, state 3 is a recommended boost that lets the controller raise storage temperatures, and state 4 is a stronger mandatory boost that pushes the heat pump to charge thermal storage as far as its limits allow.
Q: How does SG Ready load shifting differ from a simple timer schedule?
A: A timer follows your clock and knows nothing about the grid; it will happily run the heat pump during a peak. SG Ready follows an external signal, so the decision about when to charge storage comes from a utility, a dynamic tariff feed, or a home energy controller. The heat pump still uses its own schedules and weather compensation, but an outside actor can override the timing within defined states.
Q: Does SG Ready certification guarantee lower electricity bills?
A: No. It confirms the controller can receive and act on the four standard signals. Lower bills need a tariff or solar setup where those signals line up with cheaper electricity, plus enough cylinder or buffer storage for the shifted heat to be useful. SG Ready is a control feature, and its value varies with utility signals, controller setup, and the tariff in force.
Sources / References
Grid-Interactive Efficient Buildings | Department of Energy
Comments
Post a Comment