Yes, you can rent an electric car at selected locations via billiger-mietwagen.de. A relevant filter simplifies the search.
At billiger-mietwagen.de there is a separate filter for electric cars. This allows you to display only offers with this vehicle type. You will find the relevant filter on the search results page.
Here you can also find the filter "Electric" under the heading "Vehicle type" . There is also a filter for hybrid cars. The filter only appears if electric or hybrid cars are available at the selected destination. Unfortunately, no filter means no electric or hybrid car.