(Code available at harningle/useful-scripts)

I just don’t understand why we don’t have AC in Switzerland…

I saw a post somewhere claiming that the heat-related death rate in Europe is roughly the same as the gun-violence death rate in the US. I was a bit surprised and checked the Swiss data. I know there can be plenty of measurement error, but it seems to be true!1

Source: CDC WONDER. 2018--2024. Multiple Cause of Death, 2018-2024. Atlanta, GA: United States Department of Health and Human Services. https://wonder.cdc.gov/mcd-icd10-expanded.html. Federal Office for the Environment. 2026. Heat-Related Deaths. Bern, Switzerland: Federal Department of Environment, Transport, Energy and Communications. https://www.bafu.admin.ch/en/indicators.

Notes: The gun-death series includes the following ICD-10 codes: W32, W33, W34 (accidental), X93, X94, X95 (homicide), Y22, Y23, Y24 (undetermined intent), and Y35 (legal intervention). We exclude suicide here. The shade is the 95% confidence interval.

It’s getting hotter and hotter

Many people say Switzerland doesn’t have AC because it wasn’t hot in the past. Indeed. But it has been getting astonishingly hot recently in Geneva!

Source: MeteoSwiss. 2026. Climate Stations - Homogeneous Data Series. Zurich, Switzerland: Federal Department of Home Affairs. https://data.geo.admin.ch/browser/index.html#/collections/ch.meteoschweiz.ogd-nbcn/items/gve?.asset=asset-ogd-nbcn_gve_d_historical-csv.

Notes: The colour indicates the number of days with the highest temperature falling inside the temperature range in the year. This figure was generated on 2026/06/28, so we only have partial data for 2026; all previous years have full-year data.

Switzerland is a net electricity exporter in the summer

One reason against AC is the environment. I don’t think it makes sense electricity-wise. Switzerland has been a net electricity exporter during the summer for quite a few years.

Source: Swiss Federal Office of Energy. 2026. Schweizerische Elektrizitätsbilanz - Monatswerte. Bern, Switzerland: Federal Department of Environment, Transport, Energy and Communications. https://www.bfe.admin.ch/bfe/en/home/supply/statistics-and-geodata/energy-statistics/electricity-statistics.html/.

Notes: This figure plots each year's net export value since 1990. It overlays year on year with transparency. The more transparent a region, the fewer years have data there.

Source: Same as above.

Notes: Same as above, but for production and consumption.

You can argue much of the electricity comes from hydro, which eventually is from melting glaciers and snow, so not that green. You can argue that, beyond electricity, Switzerland is a net importer of energy overall. I agree AC is not green. But would you rather pollute the environment and enjoy a 28-degree room temperature, or sleep at 31 degrees and not use AC?2

My tips

Use Libraries. Many libraries have AC or are water-cooled, and most are open to the public for free, even if you are not a student.3 I’ve personally verified that Graduate Institute Library, Uni MAIL, and Uni CMU are all cool. But note they may not be open at weekends as it’s summer vacation.

Avoid Local Heavy Compute. If possible, move local compute, especially those machine learning ones, to some free cloud like Colab or Kaggle. That helps a lot. For me, the biggest heat generator is my GPU.

Bernoulli Effect. If you do feel outside is much cooler than your room, directing your fan to blow towards outside works way better than towards inside. Let the Bernoulli effect do its job.

  1. I feel the heat-related death data should be OK, but the gun-death data not so much. It may suffer from underestimation. ↩

  2. This 31 degrees Celsius isn’t hypothetical. My thermometer right now shows my bedroom is at 31 Celsius, at 2:20 a.m., with windows and door open. ↩

  3. I very much like GeniLac from SIG. Basically they use cool water from Lake Geneva to cool down the buildings. Check their video here. ↩