I'm one of those travelers who avoids self driving while on a European holiday. Public transportations, trains and coaches work well for me. But if you want to self drive, here are some Norwegian links that explain the toll systems:
Why register foreign rental / leasing cars? If you register, you as
the renter / lessee will receive the invoice directly. If you don’t
register, the invoice will be sent to the rental / leasing company.
The company may add administration fees to cover their cost of
handling the invoice and collecting the amount from the renter /
lessee. Please register to get started.
There are also tolls to enter Oslo:
Congestion charge and environmental differentiation rates apply to the
prices at Oslo's toll points:
It is more expensive to pass during rush hour, i.e. 6.30–9 am and 3–5
pm. It is more expensive to pass with a diesel vehicle, and free with
electric and hydrogen vehicles. Regular prices apply to gasoline and
You are charged every time you drive into the city, not when you drive
out of the city.
The hotels I use in Oslo, Helsinki and Copenhagen were city hotels and did not appear to have parking lots attached to the property. See:
Given the hassle and expense of driving a car into the city centers, one strategy if you must have a private car is to rent when you leave on major city and return when to get to your next major city designation. Use transit in the city and not pay to have a parked car sitting around in the metro areas.