Sweden Car Rental

Does anyone know how easy it is to find charging stations, especially
outside of the main cities?

In general pretty easy. Here is an unofficial map of charging stations: https://www.uppladdning.nu/Map.aspx?ln=sv

Do hotels provide chargers onsite?

Many do, but not all.

Do most charging stations have a fast charger?

In general they do, although not at hotels since they are probably for guest staying overnight.

How do tolls work with a rental car? Does the car come with a pass or
transponder to add the toll to the rental account?

You have to ask the rental company. I would not assume any kind of pass or transponder and you probably have to pay them yourself. But toll roads are rare in Sweden, and the only one you are likely to encounter is the Stockholm congestion charge.

However, you should probably rethink this plan a bit in my opinion. Instead of renting a car in Stockholm, take the train to e.g. Jönköping or Nässjö and rent the car there. Then return the car in Kalmar and take the train back to Stockholm. That will save you a bit of time, and the long and boring drive south from Stockholm. And you don't have to deal with the traffic around Stockholm.

Thanks Badger, that is really helpful, especially the charging station map! I will do some math and see if it makes more sense just to rent a car closer to Jönköping.

In my opinion it makes a lot more sense. I guess it will save you a bit of money. But the important reason is in my opinion that it will save you a long and boring drive. There is nothing fun about the E4 south from Stockholm, and the train is a lot faster. The E4 is also prone to congestion, so if you're unlucky driving from Stockholm can mean a lot of time spent sitting in traffic jams.

If a one way rental from Jönköping to Kalmar is expensive, consider renting a car in Linköping or Norrköping instead.

And if you're going to Norway after, returning to Stockholm does not sound like the best idea. That is a bit of a detour.

Thanks for the info Badger. I have been looking into trains and rental cars for the part of my trip away from Stockholm and you are giving me the information I need to finalize my choice!

Glad I can be of help, where are you going?