Emergency generators

Emergency power generators are used to generate electrical energy and differ in terms of their drive and mode of operation. In the following article, we explain which emergency power generators are available and how they work.

Emergency generator – briefly explained

What is an emergency generator? An emergency generator (also emergency power generator or mobile emergency power system) is a device for generating electricity that is used in the event of a failure of the regular power supply – for example, during a power outage.[1]

Emergency generators differ in terms of the type of power they provide. The most common backup power units are the following:

  • Emergency generator with diesel or gasoline (combustion engine): The liquid fuel is stored in a tank and is thus reliably available to the generator.
  • Gas emergency generator: Especially in larger plants, gas turbines are often used to drive the generators.
  • Battery-powered emergency generators: Rechargeable batteries or accumulators are often used to operate emergency generators in conjunction with an inverter. However, since these devices usually offer limited backup time, they do not always pass as emergency generators.
  • Combinations of batteries and combustion engines: In the event of a power failure, the batteries initially provide the power supply. The engines take over a little later.
  • Emergency generator with inverter:Since with inverter technology the combustion engine and generator run independently of each other, they operate at different frequencies and the emergency generator has the ability to adapt the engine speed to the amount of energy required (in partial load operation). The results are a much quieter emergency generator and lower fuel consumption. If you want to be independent in terms of power supply and are looking for an emergency generator for home, you can get a mini emergency generator. An emergency generator for a single-family home generates electricity for one’s own needs and can also be used, for example, for camping or in allotments.

Emergency generator function

The function of emergency power systems is quickly explained, as an emergency generator consists of only two basic components: an internal combustion engine (drive) and a generator (energy producer). While the engine drives the generator, the latter generates a voltage that is delivered to the user through a socket.[2]

Regardless of whether the emergency generator is powered by diesel or gas – in emergency situations such as a power outage, its job is to generate electricity for as long as possible. However, there is no one-size-fits-all answer to the question of how long the emergency generator is capable of doing this. This is due, for example, to the fact that small, compact models have a smaller tank than larger emergency gensets. Some gensets also consume more fuel than others. Models with inverter technology have the great advantage that they optimally adjust the speed downward and therefore consume less fuel.[2]

How much power should an emergency generator have? Of course, the type of consumer that you want to operate with the generator also has an influence on the power of the generator. How much power an emergency generator should have cannot be answered in a general way. For example, it makes a significant difference whether you want to operate a radio with 100 watts or an electric hotplate with 1,500 watts. In order to narrow down the power class for the emergency generator, it is therefore essential to think carefully about what you want to use the generator for before you buy it. It is advisable to plan for a 20 to 30 percent "buffer" upwards in terms of output. After all, emergency generators that deliver more power than the consumer needs are not only much quieter in operation, but also have a longer service life.[2]

Handling and testing of emergency power system

How do I connect an emergency generator? In any case, the installation of the emergency generator at the meter box should be done by an electrician. Once the distribution box has been prepared for the operation of the generator, non-professionals can then get to work. Connecting the generator is usually quick and easy. During commissioning, one should only make sure that the main fuse is switched off. In addition, the consumers must not all be switched on at the same time, but one after the other.[4]

Most smaller emergency gensets do not require grounding, i.e. discharge of electric current into the ground via a ground terminal. This is because no dangerous touch current is generated during their operation – even if contact should occur between active conductors and the genset housing. Consumers are only required to ground if there is a risk of electrostatic charge. This is the case if the power is fed into a fixed installation or the fuel is pumped through hoses.[5]

Costs emergency generator

How much a mobile power generator costs depends primarily on one’s own requirements. In addition to the type and number of devices that are to be operated with the emergency generator, the fuel also plays an important role for the price. For example, the purchase price of gasoline generators is comparatively low, but emergency generators with diesel are more durable.

In addition, the price is also determined by the required accessories. If the emergency generator is installed outdoors, a sound insulation hood is required to protect the unit and for noise protection reasons. Gensets that are placed indoors must be equipped with an exhaust hose that safely conducts the exhaust gases outdoors.[6]

Also, how much fuel a generator consumes and how many costs this incurs depends on various factors. What does an emergency generator consume? The main determining factor is the type of fuel: generators that run on diesel are more fuel-efficient than those that generate gasoline power. In addition, it is worthwhile to purchase a generator that can also be used in partial operation and consumes less fuel during this time.[7]

To find the most cost-effective emergency generator that meets 100 percent of your needs, you should consult an expert. To save effort and nerves, it is advisable to seek the advice of a specialist dealer such as SFC before making a purchase.[6]

The difference between emergency power system and UPS systems

A backup power system (or emergency generator or emergency power supply) is used to generate electrical energy from existing resources. As a rule, it is driven by a gasoline or diesel internal combustion engine, but electric drives are also available. The drive energy generated is then converted into electricity with the aid of a generator.[10]

Depending on the desired application, emergency power systems are available as stationary and mobile units. They are used where it is essential to maintain the flow of electricity during a failure of the regular power supply – for example, in hospitals and nuclear power plants, but also in private households.

UPS systems are also used for power supply. The abbreviation UPS stands for "uninterruptible power supply". The systems are used to guarantee the supply in the event of a power failure. They are used not only in hospitals and railroad signal boxes, but also in data centers and offices.

What is the difference between emergency power systems and UPS? While emergency power systems interrupt the power supply for a short time during switching, UPS systems supply power without any interruption.[11]

The solutions of SFC

How do SFC’s solutions help me when I am looking for emergency power generators? SFC Energy AG is one of the leading manufacturers of hydrogen and direct methanol fuel cells for hybrid power supply. The sustainable fuel cell producer offers its customers both methanol and hydrogen fuel cells for use as emergency power generators.[9]

Regardless of whether the fuel cell is powered by hydrogen or methanol, fuel cell technology has been gaining in importance for several years now. This is due not only to its energy efficiency and environmentally friendly fuels, but also to the fact that it is a real all-rounder in terms of application. Fuel cells provide feasible solutions for e-mobility in cars, trucks, and buses, and also show great potential in stationary applications. For example, SFC uses fuel cell technology as an emergency generator or off-grid alternative for private households or camping vacations.

The function of the fuel cell can be compared to that of a battery. As electrochemical cells, both have an anode and a cathode, but are powered by different operating materials. Fuel cell technology relies on hydrogen or methanol, which is not stored in the unit as in the battery, but is supplied to the anode from a tank. To generate electricity, both hydrogen and direct methanol fuel cells require oxygen, which is fed to the cathode. The hydrogen reacts with oxygen to form water, and the methanol reacts with the water to form carbon dioxide and H+ ions.

The biggest advantage of fuel cell technology compared to internal combustion engines is its environmental friendliness. The hydrogen fuel cell does not produce any harmful exhaust gases such as nitrogen oxides or carbon monoxide, but only waste heat and water vapor. In addition, the fuel cell operates much more quietly than conventional combustion units.

SFC already manufactures direct methanol fuel cells for private users. These are used as power generators in single-family homes, on board of motor homes and sailboats, and in vacation homes that do not have access to the conventional power grid.[8]


Emergency generators maintain the power supply in emergency situations and thus play an important role in industry, but also for private households. How long a backup power system produces electricity and how much fuel is consumed in the process depends on the size and performance of the model and the type of consumer. If you are looking for a cost-effective variant for private use, you should seek advice from a specialist dealer. SFC is a competent partner for all those who rely on environmentally friendly power production with hydrogen and methanol fuel cells.