Hamburg's weird attempt to regulate AC

At the onset of energy abundance, a German city is fighting cold air

Geographically, Germany’s second largest city Hamburg is north of the border of the continental US. So you would think heat is not that big of an issue. But Hamburg’s citizens are 13 times more likely to die from the effects of heat than people in the US: There were 2,300 heat-related deaths in Hamburg (population: 1.9 million) between 2000 and 2023, so 100 per year, or 5 per 100,000 people. According to the CDC, the yearly number in the US is 1,220 (population: 334 million), or 0.36 per 100.000 people. Why is that?

For one, Germans really don’t like AC. We believe it gives us stiff necks, colds and weakens our immune system. And there was no need – between 1961 and 1990 (that’s 29 years!), the thermometer in Hamburg crossed the 30°C/86°F mark on only 76 days. But the summers have become hotter here too, and from 1991 to 2020, the number more than doubled to 185 days above 30°C/86°F.

So Germans are looking for ways to cool down. And the most popular newspaper BILD started to publish the same illustration every year that shows how to construct a makeshift AC:

A fan is directed towards a wet cloth. Moisture evaporates and creates cold.

It’s a ludicrous setup and barely works – I’ve tried. Another common tip is to cover windows with rescue blankets from the outside. If one can ignore the tinfoil hat vibes it does help. But landlords are allowed to ban the practice, and in a country of renters rather than owners (53% to 47%) it’s a discussion some prefer to avoid.

Barely Used: AC In Germany

The obvious solution for everyone outside of Germany would be to install an AC unit. And demand is slowly picking up. They come in several forms but the two most commonly used in Germany are split-system AC and portable AC. Split-system AC consists of a compressor mounted outside, and an evaporator mounted inside. A cable and a coolant tube connects the two:

A portable AC unit contains all parts in a single box. While easy to deploy, they have a huge disadvantage. Heat is generated in the form of hot air rather than hot coolant in a tube. The most common solution is to open a window and cover it with a piece of plastic. A large hose is attached that transfers the hot air from the unit and out of the window:

Of course, single sheet of plastic provides nowhere near as much insulation as the double- or triple-glazed windows that are common in Germany. More warm air flows inside, making portable AC unit some of the most inefficient ways to cool a room.

Regulating Cold Air

Now which one of the two solutions is Hamburg trying to regulate into non-existence? The main culprit is the Behörde für Umwelt, Klima, Energie und Agrarwirtschaft or Bukea in short (translates roughly to Agency for Environment, Climate, Energy, and Agriculture. It is one of 11 agencies that make up the Hamburg government (also a federal state in Germany). As described in a recent article in Die Zeit weekly newspaper, Bukea believes AC units to be “climate catastrophes” that guzzle energy and heat up the environment. So it decided to try and limit their installation, using the Hamburg Climate Protection Act.

Since 2024, §13 requires independent energy consultants. They must verify that installing a split-system AC unit is the most economic way to reach the desired maximum room temperature. “Economic” here means that the long-term costs are lower than the long-term savings. Depending on how you define the maximum room temperature and project energy prices over the next 10 years or so, window blinds will always come out on top.

Hamburg’s law is in addition to plentiful federal regulation already. Most split-system AC units contain a coolant that, if evaporated into the air, contributes to the greenhouse effect. Only certified companies are allowed to install AC. Online shops that sell split-system AC units to private customers are required to ask for written confirmation that they will be installed by certified personnel.

A Post-Fukushima Policy

Two forces are at work here. First is some degree of regulatory capture. There are very strong trade cooperatives and guilds that publish best practices and norms. While they are technically not law, they are relied upon by the judiciary as a benchmark when assessing disputes. By tightening norms, these organizations have some degree of influence over regulations. Stricter regulations limit the number of market participants and leads to increasing prices.

More interesting is the second force. After the Fukushima disaster and for various political reasons, nuclear power was phased out. At the time production costs of renewable energy were much higher than they are today. The basic deal between the German government and its people following the decision can be rewritten like this: You'll pay higher prices per kWh while we help you save energy. Since then, successive governments introduced subsidy programs for insulating homes, new heating appliances, wall boxes, EVs, PV, battery storage etc. That defines the energy transition as a transition to consume less energy, rather than more.

Energy Consumption As A Development Marker

Historically the more developed a country is the more energy it consumes (see Vaclav Smil, Energy & Civilization for more). Germany has been bucking the trend for some years now:

Its energy consumption has come down, alongside greenhouse gas emissions. Despite large energy savings, GDP has been growing steadily.

Saving Energy When Prices Are Negative?

However, in the case of AC usage during hot summer days, that energy savings strategy is misguided and costs more lives than necessary. The Renewable Energy Sources Act (EEG) has subsidized production of renewable energy, especially solar. In fact, Germany’s solar capacity is so extensive that, on sunny summer days, the country often produces more electricity than it can immediately use. This oversupply has led record number of days with negative prices.

Despite this abundance, the fear of overconsumption persists, driving policies that discourage the use of energy-intensive appliances like air conditioners. But this overlooks a crucial point: technological advancements in energy storage have the potential to turn this surplus into a lifesaving asset.

The Role of Energy Storage

In the past, the intermittent nature of renewable energy—solar power only during the day, wind power when it’s windy—was a significant limitation. However, the growing adoption of energy storage solutions, especially batteries, is transforming this landscape. Large-scale battery systems can store excess energy generated during peak production times, such as sunny afternoons, and release it when demand is high, like during hot summer evenings when people need cooling. The same applies to residential batteries paired with rooftop PV.

The benefits of this are twofold. First, it ensures that renewable energy isn’t wasted during periods of negative pricing, making the grid more efficient. Second, and more relevant to Hamburg’s AC dilemma, it allows for increased energy consumption without raising carbon emissions. When energy is abundant, cheap, and clean, using it to power air conditioning units is not just logical but lifesaving.

Policy Implications

Hamburg’s current regulatory framework does not fully account for these developments. By focusing narrowly on reducing energy consumption rather than optimizing it, the city’s policies are out of step with the realities of a rapidly evolving energy landscape. Encouraging the use of AC units during periods of excess renewable energy, particularly when paired with storage solutions, could help save lives without compromising the city’s climate goals.

Conclusion

We are about to enter the age of energy abundance. Cheap solar coupled with cheap storage will allow us to use more energy, while still reducing CO2 emissions. Hamburg’s reluctance to embrace this shift reflects an outdated mindset focused on scarcity rather than abundance. As storage technology continues to advance, it’s time to rethink how we use energy—especially when it’s free, clean, and desperately needed to cool our homes during increasingly hot summers.