An emergency power generator is used wherever there is no electricity or no power connection available. Here, we provide an overview of different types, their functions, specific requirements, as well as the advantages and disadvantages of purchasing one.
Table of Contents
What is an Emergency Power Generator?
An emergency power generator, also called a power generation unit or simply a generator, is a self-contained system for generating electrical energy. Its main function is to ensure a reliable power supply in the event of a failure of the public power grid or in locations without a built-in power connection.
An emergency power generator consists of two main components:
- Engine: Usually an internal combustion engine (petrol, diesel, gas) that generates mechanical energy
- Generator: Converts the mechanical energy from the engine into electrical energy (electricity)
The units are designed to start manually or automatically in an emergency and take over the power supply in the shortest possible time.
What Types of Emergency Power Generators Are There?
Emergency power generators can be differentiated according to different criteria.
1. Generator Design
| Type | Function | Advantages | Disadvantages | Application |
|---|---|---|---|---|
| Synchronous Generator | Generates AC directly; provides a constant frequency and voltage, but is sensitive to load fluctuations | Suitable for inductive loads (motors, pumps) and sensitive electronics (with AVR control) | More complex and expensive than asynchronous generators | Construction, industry, home supply |
| Asynchronous Generator | More robust and simpler in design; the frequency is not as stable as with the synchronous generator | Robust, low-maintenance, more affordable | Not ideal for sensitive electronics; can have problems with inductive loads | Construction sites, simple tools |
| Inverter Generator | First generates DC, which is then converted into pure sine wave AC via an inverter | Delivers a very clean and stable voltage/frequency; fuel-efficient by adjusting engine speed to the load | Higher purchase price | Sensitive electronics (computers, laptops, modern heating systems), camping |
2. Fuel Type
- Petrol Generators: Common for smaller, mobile devices; easy to start, but petrol has limited storage life
- Diesel Generators: Dominant for medium and large, stationary systems; diesel is safer to store and the engines are more durable
- Gas Generators (LPG/Natural Gas): Are often connected directly to the gas line, which allows for a very long running time
How Does an Emergency Power Generator Work?
The basic functional principle is a simple energy conversion process:
- Start-up: The internal combustion engine is started (manually or automatically).
- Mechanical Energy: The engine burns fuel (petrol, diesel, gas), thereby generating a rotational movement (mechanical energy).
- Conversion: The engine’s crankshaft is directly connected to the generator. The generator converts the mechanical rotational movement into electrical energy.
- Regulation: A control unit ensures that the generated voltage and frequency remain constant to avoid damaging connected devices.
- Feed-in: The generated electricity is fed into the house network via sockets or a permanently installed transfer switch.
When is an Emergency Power Generator Needed?
The main purpose is the safety and maintenance of critical infrastructure during power outages.
General Applications:
- Bridging Power Outages: Supplying households, hospitals, data centers, or agricultural businesses
- Mobile Power Supply: On construction sites, at events, or in agriculture where there is no grid connection
- Disaster Preparedness: Operating pumps (e.g., after floods), lighting, and communication devices
In the Context of Mobile Heating:
In the context of mobile heating systems (e.g., in the event of a heating failure, renovations, or events), emergency power generators are essential for, among other things:
- Operating the Burners: Most mobile heating systems require electricity to operate the burner, the control electronics, and the pumps.
- Fans and Blowers: For warm air generators, powerful blowers are necessary to distribute the heat. These require a reliable power source.
If the mobile heating system has to be operated in a location without a grid connection or during a power outage, the generator is the only source of power. Especially in the field of mobile heat supply, generators with outputs from 5.4 kVA to over 250 kVA are used to supply even large heating containers.
How Powerful Must an Emergency Power Generator Be for a Single-Family Home?
The required output depends heavily on which consumers are to be operated in an emergency. A distinction is made between starting power and continuous power.
Calculating the Output:
- List of Consumers: Create a list of all devices that absolutely must run (heating pump, refrigerator, light, communication devices).
- Starting Current (Inductive Loads): Devices with electric motors (refrigerators, pumps, compressors) require a multiple of their nominal power when starting (starting current). This factor can be 3 to 5. The maximum starting power of all devices starting simultaneously determines the minimum output of the generator.
- Continuous Current: The sum of the nominal powers of all devices running simultaneously determines the continuous power.
Rule of Thumb for Single-Family Homes:
For the emergency supply of an average single-family home, where only the most essential consumers (heating, refrigerator, light, internet) are to be operated, a generator with a continuous output of 5 kW (approx. 6.25 kVA) to 10 kW (approx. 12.5 kVA) is usually sufficient.
- Minimal Supply (Light, Refrigerator, Communication): approx. 2 kW (approx. 2.5 kVA) – 3 kW (approx. 3.75 kVA)
- Comfort Supply (incl. Heating, Stove, Hot Water): approx. 5 kW (approx. 6.25 kVA) – 10 kW (approx. 12.5 kVA)
It is advisable to choose a synchronous or inverter generator, as this provides a more stable voltage, which is important for modern heating controls and sensitive electronics.
Does it Make Sense to Buy an Emergency Power Generator?
The purchase of an emergency power generator is an insurance measure against the consequences of a prolonged power outage. The sensibility depends on individual risk tolerance and potential damages:
| Argument | Pro Purchase | Contra Purchase |
|---|---|---|
| Safety | Protection against failure of critical systems (heating, water supply, medical devices) | Power outages in Germany are rare and usually short |
| Cost | One-time purchase that can prevent major damage in an emergency (e.g., frost damage to the heating system) | High purchase costs, running costs for fuel, maintenance, and storage |
| Comfort | Maintenance of a certain standard of living (cooking, light, communication) | Noise pollution, emissions (exhaust fumes), storage of fuel |
| Application | Immediate availability and independence | Installation (feeding into the house network) must be carried out by qualified personnel |
Conclusion: For homeowners who live in a rural area, rely on a functioning heating system, or operate sensitive medical devices, the purchase of an emergency power generator is a sensible investment. For short-term, one-off use (e.g., for a construction project), renting a generator may be the more economical solution.
References:
SFC. (seen on 10/16/2025). Notstromaggregat | Einfach erklärt.
Ho-Ma Nostrom. (seen on 10/16/2025). Auf Stromausfälle vorbereitet: Wie funktioniert ein Notstromaggregat?
Bauer Generatoren. (seen on 10/16/2025). Welches Notstromaggregat für Ihr Einfamilienhaus?
MVV Energie. (seen on 10/16/2025). Notstromaggregat: sinnvoll oder nicht?
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