Heat pumps are considered an efficient and future-proof heating solution. What is often overlooked in everyday life: Without electricity, even the best heat pump stands still. Especially in single-family homes, agricultural properties, or commercial buildings, the question therefore arises as to which emergency power generator is suitable to reliably keep a heat pump running during a power outage. The requirements are higher than for many other household consumers.
Fundamentals: Why heat pumps place special demands
A heat pump is not a simple consumer. It consists of several electrical components such as compressors, circulation pumps, controls, and sometimes electric auxiliary heaters. The most crucial factor here is the starting current of the compressor. This is significantly higher than the normal operating power and must be reliably supplied by the emergency power generator without voltage or frequency drops.
An undersized generator often leads to:
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the heat pump not starting
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protection mechanisms being triggered
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the electronics being disturbed or damaged
Correctly sizing power – more than just comparing kW
When selecting a suitable emergency power generator, it is not enough to just look at the rated power of the heat pump. More important are:
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Starting power (inrush current) of the heat pump
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Type of compressor (On/Off or inverter)
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Additional consumers that are to be supplied in emergency power mode
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Simultaneity of loads
In practice, this means:
An emergency power generator should be significantly more powerful than the pure electrical connection power of the heat pump suggests. Depending on the system type, a power reserve of 30–100% may be useful or even necessary.
Single-phase or three-phase – crucial for practical use
Many heat pumps, especially larger systems, operate three-phase (400 V). Accordingly, the emergency power generator should also be three-phase. However, an often underestimated issue arises: unbalanced load.
Unbalanced load with emergency power generators
An unbalanced load occurs when the three phases of a power generator are unequally loaded. In practice, this often happens when:
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the heat pump is operated three-phase
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single-phase household consumers (lights, refrigerator, sockets) are connected to individual phases at the same time
Many power generators have limited unbalanced load capability. If one phase is significantly more loaded than the others, the generator can shut down or be damaged. For emergency power operation with a heat pump, it is therefore important:
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high permissible unbalanced load of the generator
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clean load distribution in the house network
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if necessary, clear separation between the heat pump and other consumers
Especially with permanently installed emergency power solutions, this topic should be considered already in the planning phase.
Do not underestimate voltage and frequency stability
Modern heat pumps have sensitive electronics. A suitable emergency power generator must therefore:
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supply a stable voltage
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keep the frequency constant even with load changes
Inverter technology or high-quality conventional generators with good regulation (AVR) clearly have an advantage here. Cheap or very simple power generators are usually unsuitable for operating heat pumps.
Conclusion: The right emergency power generator for heat pumps
An emergency power generator for a heat pump must be able to do more than just "supply electricity". Crucial factors are sufficient power reserves, clean voltage, stable frequency, and controlled handling of unbalanced loads in three-phase systems. If you also want to supply household consumers, you should consider the entire system and not just individual components.
Properly sized, an emergency power generator ensures that heating, hot water, and essential consumers continue to run reliably even during extended power outages.