Good day!
Due to the power outage in southern Berlin, my father considers it necessary to examine to what extent it is possible to prepare for such an event, and he has asked me to gather relevant information. Before I speak with an electrical contractor, I would like to understand the technical and legal conditions under which this could be done.
It is important to distinguish between a "temporary solution" (where only the heating system is powered) and a proper installation (where the entire house is supplied). Additionally, one should clarify whether major appliances such as the stove and oven are included or not.
In theory, a diesel generator (with HVO 100 fuel in the tank to prevent degradation) could suffice if a supply connection point has been created at both houses, for example under a stair landing or similar. The supply lines to the heating systems would then be disconnected (each originating from the emergency switch) and connected to the supply point, while the generator runs outside.
A proper installation as part of the overall system would, however, need to ensure that when the generator is in use, the connection to the public grid is simultaneously disconnected. This is necessary firstly to prevent backfeeding, and secondly because the grid power would eventually be restored.
I don’t believe that a well-insulated house would cool down enough over a week for the heating pipes to freeze, but he wants me to clarify this.
Thank you, Matthias!
Due to the power outage in southern Berlin, my father considers it necessary to examine to what extent it is possible to prepare for such an event, and he has asked me to gather relevant information. Before I speak with an electrical contractor, I would like to understand the technical and legal conditions under which this could be done.
It is important to distinguish between a "temporary solution" (where only the heating system is powered) and a proper installation (where the entire house is supplied). Additionally, one should clarify whether major appliances such as the stove and oven are included or not.
In theory, a diesel generator (with HVO 100 fuel in the tank to prevent degradation) could suffice if a supply connection point has been created at both houses, for example under a stair landing or similar. The supply lines to the heating systems would then be disconnected (each originating from the emergency switch) and connected to the supply point, while the generator runs outside.
A proper installation as part of the overall system would, however, need to ensure that when the generator is in use, the connection to the public grid is simultaneously disconnected. This is necessary firstly to prevent backfeeding, and secondly because the grid power would eventually be restored.
I don’t believe that a well-insulated house would cool down enough over a week for the heating pipes to freeze, but he wants me to clarify this.
Thank you, Matthias!
Just a note about what happened to us around the turn of the year regarding this issue.
Due to capacity reasons, our department temporarily relocated in mid-December to an older office building within an industrial complex. Shortly after, there was a power outage in the city area. Apparently, the medium-voltage system supplying our office building and the surrounding production halls of other companies was damaged. The repair of the medium-voltage system took an astonishingly long time—over one month.
In the meantime, our company’s own diesel generator was connected to our office building, so we were actually able to switch back from working from home to the office at the beginning of January.
However, there were regularly double-digit negative temperatures (Celsius) during that period, and the generator froze. I have no idea whether the winter/summer diesel issue played a role here, but I suspect this was fixed after the first failure at the latest, yet it happened several times anyway.
After that, we were asked to switch back to working from home until the final repair of the medium-voltage system was completed.
I have no idea what the surrounding production companies did. Their energy demand is likely much higher than that of our office building.
What I want to say with this is that even if you prepare, things can still go differently in an emergency than you expected, because such a solution naturally also needs to be regularly maintained and, if necessary, must work under extreme conditions.
Due to capacity reasons, our department temporarily relocated in mid-December to an older office building within an industrial complex. Shortly after, there was a power outage in the city area. Apparently, the medium-voltage system supplying our office building and the surrounding production halls of other companies was damaged. The repair of the medium-voltage system took an astonishingly long time—over one month.
In the meantime, our company’s own diesel generator was connected to our office building, so we were actually able to switch back from working from home to the office at the beginning of January.
However, there were regularly double-digit negative temperatures (Celsius) during that period, and the generator froze. I have no idea whether the winter/summer diesel issue played a role here, but I suspect this was fixed after the first failure at the latest, yet it happened several times anyway.
After that, we were asked to switch back to working from home until the final repair of the medium-voltage system was completed.
I have no idea what the surrounding production companies did. Their energy demand is likely much higher than that of our office building.
What I want to say with this is that even if you prepare, things can still go differently in an emergency than you expected, because such a solution naturally also needs to be regularly maintained and, if necessary, must work under extreme conditions.
J
Jesse Custer9 Feb 2026 10:02At the end of the day, you have two options:
- The heating system becomes disconnectable – this is the cheapest option. Instead of a direct connection, the heating system’s cable basically has a plug, which then goes into a socket. If you unplug it in case of a power failure, you can simply connect an emergency generator. Problem solved – as long as the heating system can handle the generator’s power supply (keyword stability / continuity / frequency). In such cases, a small buffer battery is often used in between...
- However, if you want to equip an entire house with a certain level of supply security, you first need a transfer switch box, for example from enwitec. This device disconnects the house’s main electrical system from the grid in the event of a power outage. Behind it, there must be an appropriate power supply, such as a battery with an inverter (often connected to a solar system), which draws its energy from the battery (something has to be "there" first) and then provides a connection for an external generator. Such a system runs as long as you have fuel.
But based on the last solution, also be aware of the following:
- You will attract attention from outsiders – a large generator is noisy...
- You need fuel – and quite a lot of it. Expect about 1 liter per kW per hour, which means roughly 24 liters per day at 1 kW, which may not even be enough.
In the case of Berlin, that’s not a problem – you just drive once a day to a neighboring area where there is still power and fill up a few spare jerry cans. For myself, however, in the event of a widespread outage, it looks different – I have, at best, about 200 liters of fuel available (2 cars, 4 motorcycles, 40 liters in spare cans)...
... so, in the event of an attack from space, that’s already pretty tight...
And before anyone gets the wrong idea: no, I’m not a prepper – we simply have solar with emergency power, which I have thought through a bit more…
Addendum – I forgot:
- I would estimate solution 1 at about 5,000 euros – electrician and installation materials, a decent battery, and a decent generator
- Solution 2, depending on the battery and generator, will definitely run into five figures.
- The heating system becomes disconnectable – this is the cheapest option. Instead of a direct connection, the heating system’s cable basically has a plug, which then goes into a socket. If you unplug it in case of a power failure, you can simply connect an emergency generator. Problem solved – as long as the heating system can handle the generator’s power supply (keyword stability / continuity / frequency). In such cases, a small buffer battery is often used in between...
- However, if you want to equip an entire house with a certain level of supply security, you first need a transfer switch box, for example from enwitec. This device disconnects the house’s main electrical system from the grid in the event of a power outage. Behind it, there must be an appropriate power supply, such as a battery with an inverter (often connected to a solar system), which draws its energy from the battery (something has to be "there" first) and then provides a connection for an external generator. Such a system runs as long as you have fuel.
But based on the last solution, also be aware of the following:
- You will attract attention from outsiders – a large generator is noisy...
- You need fuel – and quite a lot of it. Expect about 1 liter per kW per hour, which means roughly 24 liters per day at 1 kW, which may not even be enough.
In the case of Berlin, that’s not a problem – you just drive once a day to a neighboring area where there is still power and fill up a few spare jerry cans. For myself, however, in the event of a widespread outage, it looks different – I have, at best, about 200 liters of fuel available (2 cars, 4 motorcycles, 40 liters in spare cans)...
... so, in the event of an attack from space, that’s already pretty tight...
And before anyone gets the wrong idea: no, I’m not a prepper – we simply have solar with emergency power, which I have thought through a bit more…
Addendum – I forgot:
- I would estimate solution 1 at about 5,000 euros – electrician and installation materials, a decent battery, and a decent generator
- Solution 2, depending on the battery and generator, will definitely run into five figures.
M
MachsSelbst9 Feb 2026 21:11Also keep in mind:
In a real emergency—such as an extended power outage or even worse situations—your system will become the number one attraction point. This fact is often forgotten or deliberately ignored.
If the entire neighborhood is at risk of freezing during winter with outdoor temperatures of -10°C (14°F), people won’t stay quietly in their cold, dark homes; they will come knocking at your door. At first politely, but if you don’t respond, they may quickly try to break in with a hammer or a shovel.
This is similar to the misconception that having a weapon at home or carrying one will protect you. In reality, people with weapons are more likely to be killed during an assault because the situation escalates faster, often even as a result of their own weapon.
Save yourself the 10,000 to 20,000 euros and instead spend that money on food 100 or 200 times. It supports local restaurants and benefits you much more than an expensive system that will probably never be needed—and if it is, could even put your life at real risk.
In a real emergency—such as an extended power outage or even worse situations—your system will become the number one attraction point. This fact is often forgotten or deliberately ignored.
If the entire neighborhood is at risk of freezing during winter with outdoor temperatures of -10°C (14°F), people won’t stay quietly in their cold, dark homes; they will come knocking at your door. At first politely, but if you don’t respond, they may quickly try to break in with a hammer or a shovel.
This is similar to the misconception that having a weapon at home or carrying one will protect you. In reality, people with weapons are more likely to be killed during an assault because the situation escalates faster, often even as a result of their own weapon.
Save yourself the 10,000 to 20,000 euros and instead spend that money on food 100 or 200 times. It supports local restaurants and benefits you much more than an expensive system that will probably never be needed—and if it is, could even put your life at real risk.
In der Ruine10 Feb 2026 06:56I also believe that a fireplace and a photovoltaic system with a battery and emergency power function provide enough light and power for the freezer.
Thank you for all the helpful thoughts—I basically see it the same way. My father is quite old and ill, which probably explains his particular perspective on all kinds of problems that he prefers to block out. His entire house is secured with all kinds of crossbar locks and rods on the windows to prevent break-ins. I find it really annoying, especially since he considers anyone who can’t follow his line of thought to be clueless.
As a gesture of goodwill, showing that I’m taking care of his concerns, I plan to suggest installing an external power feed point on both houses. This way, if needed, the two heating systems can be powered from outside. Does anyone have an idea of the approximate power requirements for a roughly 25-year-old Viessmann oil-fired central heating system with burner, control unit, and circulation pump?
A relatively small generator should be sufficient in any case, and if it’s fueled with HVO100 and started every six months or so, it should remain operational.
For my own house, I would much rather consider a small UPS to at least be able to shut down computers safely. While you wouldn’t be able to continue working during a power outage, you would at least avoid further damage. The most realistic scenario is that an excavator might accidentally cut a cable, which would then be repaired within a few hours.
As a gesture of goodwill, showing that I’m taking care of his concerns, I plan to suggest installing an external power feed point on both houses. This way, if needed, the two heating systems can be powered from outside. Does anyone have an idea of the approximate power requirements for a roughly 25-year-old Viessmann oil-fired central heating system with burner, control unit, and circulation pump?
A relatively small generator should be sufficient in any case, and if it’s fueled with HVO100 and started every six months or so, it should remain operational.
For my own house, I would much rather consider a small UPS to at least be able to shut down computers safely. While you wouldn’t be able to continue working during a power outage, you would at least avoid further damage. The most realistic scenario is that an excavator might accidentally cut a cable, which would then be repaired within a few hours.
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